essay on dietary supplements

• - Google Chrome

Intended for healthcare professionals

• Access provided by Google Indexer
• My email alerts
• BMA member login
• Username * Password * Forgot your log in details? Need to activate BMA Member Log In Log in via OpenAthens Log in via your institution

Search form

• Advanced search
• Search responses
• Search blogs
• News & Views
• Health effects of...

Health effects of vitamin and mineral supplements

Read our food for thought 2020 collection.

• Related content
• Peer review
• Fang Fang Zhang , associate professor 1 ,
• Susan I Barr , professor 2 ,
• Helene McNulty , professor 3 ,
• Duo Li , professor 4 ,
• Jeffrey B Blumberg , professor 1
• 1 Friedman School of Nutrition Science and Policy, Tufts University, Boston, USA
• 2 University of British Columbia, Vancouver, Canada
• 3 Nutrition Innovation Centre for Food and Health, Ulster University, Coleraine, UK
• 4 Institute of Nutrition and Health, Qingdao University, Qingdao, China
• Correspondence to: F F Zhang fang_fang.zhang{at}tufts.edu

Growing numbers of healthy people are taking dietary supplements but there is little evidence that they protect against non-communicable diseases, say Fang Fang Zhang and colleagues

Vitamin and mineral supplements are the most commonly used dietary supplements by populations worldwide. 1 2 3 4 The amount of micronutrients they provide ranges from less than recommended intakes to much more, making them important contributors to total intakes. While supplements can be used to correct micronutrient deficiency or maintain an adequate intake, over-the-counter supplements are most often taken by people with no clinical signs or symptoms of deficiency. However, the effect of vitamin and mineral supplements on the risk of non-communicable diseases in “generally healthy” populations is controversial. We examine patterns of supplement use and the evidence on their effects from randomised trials.

Who uses supplements?

Vitamin and mineral supplements have a large worldwide market, but we will focus on their use in North America and Europe, where there is most evidence on patterns of use and health outcomes. The use of vitamin, mineral, and fish oil supplements 5 is common among adults in North America ( fig 1 ). 6 The prevalence of use has increased for some individual nutrients—for example, there was a fourfold increase in use of vitamin D supplements among US adults from 1999 to 2012, excluding intake obtained from multivitamin and mineral. 7 The use of omega-3 fatty acid supplements also increased sevenfold. 7

Proportion of US adults taking commonly vitamin, mineral, and fish oil supplements, National Health and Nutrition Examination Survey 1999-2014 6

• Download figure
• Open in new tab
• Download powerpoint

Supplement use is generally less prevalent in other countries than in the US and Canada but varies widely (eg, Denmark 51%, South Korea 34%, Australia 43%, UK 36%, Spain 6%, Greece 2%). 2 3 4 Different methods for assessing supplement use may contribute to the different prevalence in high income countries. National survey data for supplement use in the general population remain scarce for low and middle income countries.

Supplement use varies considerably among population subgroups within North America and Europe. In the US, >70% of adults aged ≥65 years use supplements 8 compared with a third of children and adolescents. 9 More women than men use supplements. 6 Supplement use correlates positively with educational and socioeconomic status. 10 It also clusters with healthy lifestyle factors such as not being a smoker or heavy drinker, not being overweight or obese, and being physically active. 6 Importantly, people who use supplements tend to have a better overall diet quality than those who don’t use them and their nutrient intake from foods mostly meets recommended intake levels. 11 12

Are supplements needed?

Use of supplements contributes substantially to total vitamin and mineral intakes at the population level. 13 Intake of vitamin B 6 , thiamin, and riboflavin among US adults is at least five times higher from supplements than from foods, and intakes are 15 to 20 times higher for supplements for vitamins B 12 and E. 6 Consequently, supplement use considerably reduces the proportion of the general population with inadequate nutrient intake ( box 1 ).

Population nutrient intake—definitions

Estimated average requirement is the daily level of nutrient intake estimated to meet the requirement of half of healthy people in a population

Inadequate nutrient intake —The population prevalence of inadequate intake is estimated as the percentage of the population with nutrient intake below the estimated average requirement

Tolerable upper intake is the highest daily nutrient intake that is likely to pose no risk of adverse health effects to almost all healthy people in a population. As intake increases above the upper level, the potential risk of adverse effects increases.

Excess intake —The population prevalence of excess intake is estimated as the percentage of the population with nutrient intake above the upper level

This is especially true for vitamins and minerals identified as “shortfall” nutrients such as calcium and vitamin D ( fig 2 ). 14 Despite the high use of supplements, inadequate intakes of micronutrients are still common in high income countries, where dietary patterns are typically energy rich but nutrient poor.

Prevalence of inadequate and excess nutrient intake among US Adults, National Health and Nutrition Examination Survey 1999-2014 6

In low and middle income countries, where specific micronutrient deficiencies are prevalent (eg, of iodine, iron, zinc, and vitamin A), supplementation is recommended when food based approaches such as dietary modification, fortification, or food provision are unable to achieve inadequate intake. 15 In the US and other countries, food fortification and enrichment such as the addition of iodine to salt, vitamin D to milk, and B 1 and B 3 vitamins to refined flour have contributed to the virtual elimination of their syndromes of deficiency (goitre, rickets, beriberi, and pellagra, respectively). 16 17

The widespread use of vitamin and mineral supplements in high income countries seems to contribute to an increase in population prevalence of intake above the upper tolerable level ( box 1 ). 6 Although the overall proportion of US adults with intakes above the upper level is below 5% for most nutrients ( fig 2 ), some population subgroups may have high rates of excess intake. For example, in a Canadian national survey, over 80% of children aged 1-3 years who took dietary supplements consumed vitamin A and niacin at levels above the upper limit. 18 In the US, excessive intake was noted for vitamin A (97%) and zinc (68%) among toddlers who were given supplements. 19 High quality evidence is lacking on the long term adverse effects of excess intake for several nutrients so it is unclear whether this is a cause for concern.

Do supplements protect against non-communicable diseases?

It remains controversial whether supplements are effective in reducing the risk of non-communicable diseases. In contrast to results of observational studies, the accumulated evidence from randomised controlled trials does not support benefits of supplements in reducing risks of cardiovascular disease, cancer, or type 2 diabetes in healthy people with no clinical nutritional deficiencies.

Cardiovascular disease

An updated systematic review of 15 randomised trials published after the 2013 US Preventive Service Task Force (USPSTF) review 20 confirmed the lack of benefits of supplements on cardiovascular events, mostly among patients with risk factors. 21 Although randomised trials of folic acid, alone or in combination with vitamins B 12 or B 6 , found significant reductions in plasma homocysteine levels, total cardiovascular events were not reduced. Another systematic review reported a reduced risk of stroke in association with supplementation of homocysteine lowering B vitamins, 22 but the result was largely driven by one large trial in China. 23 Overall, there is no consistent evidence to support the use of antioxidant supplements for reducing cardiovascular risk. 22 24

The Vitamin D and Omega-3 Trial (VITAL), one of the few randomised trials of supplements for primary prevention of cardiovascular disease, found no effect of vitamin D supplementation (2000 IU/day) on its primary endpoint (myocardial infarction, stroke, or cardiovascular death) in healthy people. 25 Previous large scale trials such as the Women’s Health Initiative Calcium and Vitamin D Supplementation Study 26 and the Vitamin D Assessment Study 27 also showed vitamin D supplements, alone or in combination with calcium, had no effect on cardiovascular risk.

Supplementation with omega-3 fatty acids (1 g/day) did not reduce the risk of major cardiovascular events among healthy people in the VITAL trial. 28 However, benefits were found for some secondary endpoints such as total myocardial infarctions. This result is largely consistent with findings from meta-analyses that fish oil supplementation did not have substantial effects on the primary or secondary prevention of cardiovascular disease. 29 30 However, a meta-analysis including the most recent trials reported a significant reduction in risk of myocardial infarction. 31 Further studies are needed to determine whether fish oil supplementation has a greater effect on risk of heart disease than of stroke. 32

Current evidence does not support a role of vitamin and mineral supplements in reducing cancer risk, with some evidence suggesting potential harm. β-Carotene supplementation increased the risk of lung cancer among high risk individuals in two randomised trials. The α-Tocopherol, β-Carotene Cancer Prevention Study reported an 18% increase in relative risk among smokers randomised to β-carotene (20 mg/day) compared with those who did not. 33 The β-Carotene and Retinol Efficacy Trial found that β-carotene (30 mg/day) plus vitamin A as retinol (25 000 IU/day) increased risk by 28% among smokers and workers with occupational exposure to asbestos. 34 The Selenium and Vitamin E Cancer Prevention Trial found that vitamin E (400 IU/day) supplementation was associated with a 17% increase in prostate cancer risk among men. 35

Although maternal folic acid supplementation has been proved to reduce the risk of neural tube defects, concerns have been raised that high folic acid exposure may promote cancer progression, especially in countries with mandatory fortification. 36 Most notably, folic acid supplementation at ≥1 mg/day may promote the growth of undiagnosed colorectal adenomas. 37 However, a meta-analysis of 11 randomised trials concluded that folic acid supplementation neither increased nor decreased site specific cancer risk within the first five years of supplementation. 38

Randomised trials have failed to detect a benefit of vitamin D supplementation, alone or combined with calcium, on cancer risk at either high or low doses 25 39 despite some evidence suggesting reduced total cancer mortality. 25 40 The limited evidence on fish oil supplementation suggests it does not reduce cancer risk. 28 41

Type 2 diabetes

Current evidence does not support the use of supplements with vitamins C or E, β-carotene, or fish oil to reduce the risk of type 2 diabetes, although the overall evidence from randomised trials is limited. 42 43 A recent placebo controlled trial of vitamin D supplementation (4000 IU/day) failed to reduce the risk of type 2 diabetes despite significantly increasing serum 25-hydroxyvitamin D concentrations. 44

Osteoporosis

Recent evidence regarding the effects of vitamin D and calcium supplementation is inconsistent. A meta-analysis of trials in community living older adults found that vitamin D or calcium supplementation did not reduce the risk of hip fracture or total fracture, 45 whereas another meta-analysis reported that while vitamin D alone did not reduce fracture risk, combined calcium and vitamin D supplementation decreased the relative risk of hip fracture (16%) and all fractures (6%) among older adults. 46 Ongoing research is assessing the effect of high dose vitamin D supplements on several health outcomes, including fractures, 46 but a recent three year trial of 400, 4000, or 10 000 IU/day reported that the higher doses reduced volumetric bone density, suggesting potential for harm. 47 In the absence of clear evidence on supplementation, it is prudent to ensure that dietary recommendations on calcium and vitamin D intakes are met through food and supplementation.

To date, randomised trials have largely shown no benefit of vitamin, mineral, and fish oil supplements on the risk of major non-communicable diseases in people without clinical nutritional deficiency. These results contrast with findings from observational studies, where supplemental nutrient intakes are often associated with a reduced risk of these diseases. The apparent associations from observational studies may result from unknown or unmeasured confounding factors such as socioeconomic status and lifestyle factors, including a better overall diet.

Although randomisation reduces confounding, relying exclusively on the results of randomised trials also has limitations. Trials are often conducted among high risk populations with pre-existing conditions, so the findings may not be applicable to healthy individuals. Supplements may also have health benefits for population subgroups, such as people with inadequate nutrient intake from foods, but randomised trials are not usually designed to evaluate subgroup differences. Furthermore, financial and practical constraints mean that most trials are able to investigate only a single dose, which may result in selection of a dose that is either too low (no efficacy) or too high (untoward outcomes).

Nutrients obtained from foods and supplements may confer different health effects. The Cancer Prevention Study (CPS)-II Nutrition Cohort found that supplemental calcium intake at ≥1000 mg/day was associated with an increased risk of all-cause mortality in men whereas high levels of calcium intake from foods had no harm. 48 Among US adults in the National Health and Nutrition Examination Survey, adequate intake of nutrients from foods, but not supplements, was associated with a lower risk of all-cause mortality. 6 The benefits of nutrient intake from foods may reflect synergistic interactions among multiple nutrients and other bioactive substances in foods.

The effect of supplements in specific populations warrants further investigation. Older adults are at an increased risk of malnutrition because of reduced nutrient intake and age related decreases in the bioavailability of some micronutrients. Vitamin D supplementation is recommended for breastfed infants before the introduction of whole milk and solid foods. Supplements may be more effective in reducing the risk of non-communicable disease in specific ethnic groups or people with low micronutrient intake from foods. 28 With a recent increase in the proportion of people reporting that they follow restricted dietary patterns such as ketogenic, Palaeolithic, vegan, and vegetarian diets, the value of supplements to meet the needs of these specific populations requires evaluation. In addition, potential nutrient-gene interactions have rarely been examined in studies of dietary supplements. Future studies on the role of nutrigenetics should help refine and personalise targeted recommendations for supplement use ( box 2 ).

Areas for research in vitamin and mineral supplementation

Differing health effects of nutrients obtained from foods versus supplements

Synergistic interactions among multiple nutrients and with other bioactive substances

Subpopulation studies (eg, elderly people, ethnic groups, vegans)

Nutrigenetics and “omics” sciences

Personalised supplementation

Specific needs in low and middle income countries

It is also important to recognise that the need for nutrient supplements is different in countries where nutrition deficiency is common. Ensuring adequate nutrition through food fortification and nutrient supplementation can be crucial to prevent serious adverse outcomes of nutrient deficiencies in low and middle income countries, especially among children <5 years, for whom malnutrition contributes to more than half their deaths. 15

In summary, current evidence does not support recommending vitamin or fish oil supplements to reduce the risk of non-communicable diseases among populations without clinical nutritional deficiency. Continuing efforts are warranted to further understand the potentially different roles of nutrients from foods versus supplements in health promotion among a generally healthy population as well as individuals or groups with specific nutritional needs, including those living in low and middle income countries. These efforts, coupled with the integration of new research approaches, will better inform clinical practice and public health policies.

Key messages

Randomised trial evidence does not support use of vitamin, mineral, and fish oil supplements to reduce the risk of non-communicable diseases

People using supplements tend to be older, female, and have higher education, income, and healthier lifestyles than people who do not use them

Use of supplements appreciably reduces the prevalence of inadequate intake for most nutrients but also increases the prevalence of excess intake for some nutrients

Further research is needed to assess the long term effects of supplements on the health of the general population and in individuals with specific nutritional needs, including those from low and middle income countries

Contributors and sources: All authors contributed to drafting the manuscript, with FFZ taking a lead role and serving as the guarantor. Sources of information for this manuscript included published articles based on national surveys, systematic reviews, and primary research of randomised controlled trials and prospective cohort studies. All authors contributed to critical revision of the manuscript for important intellectual content and approved the final manuscript.

Competing interests: All authors have read and understood BMJ policy on declaration of interests and declared the following: FFZ declares funding from the National Institutes of Health, NIMHD (R01 MD 011501) and the Bristol Mayer Squibb Foundation (Bridging Cancer Care Programme). DL declares funding from the National Natural Science Foundation of China (NSFC 81773433) and Key Scientific Research Projects in Shandong Providence China (2017YYSP007). JBB declares funding from Danone. HM declares funding from DSM Nutritional Products, Switzerland. The funders had no role in the design or conduct of the study, collection, management, analysis, or the interpretation of the data. JBB reports service on scientific advisory boards of AdvoCare International, California Prune Board, California Walnut Commission, Church and Dwight, Cranberry Marketing Committee, Guiding Stars, Quaker Oats, Segterra, and SmartyPants, not related to this work.

Provenance and peer review: Commissioned; externally peer reviewed.

This article is part of series commissioned by The BMJ. Open access fees are paid by Swiss Re, which had no input into the commissioning or peer review of the articles. T he BMJ thanks the series advisers, Nita Forouhi, Dariush Mozaffarian, and Anna Lartey for valuable advice and guiding selection of topics in the series.

This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/ .

• MacLennan GS ,
• Avenell A ,
• Bolland M ,
• RECORD Trial Group
• Braaten T ,
• Hjartåker A ,
• O’Brien SK ,
• Malacova E ,
• Sherriff JL ,
• Clarke TC ,
• Barnes PM ,
• Stussman BJ ,
• Blumberg JB ,
• Kantor ED ,
• Giovannucci EL
• Fulgoni VL ,
• Weaver CM ,
• Alexander GC ,
• Guadamuz JS ,
• Bailey RL ,
• Fulgoni VL 3rd . ,
• Harrison RA ,
• Pattison DJ ,
• Murphy SP ,
• West KP Jr . ,
• Institute of Medicine Committee on Use of Dietary Reference Intakes in Nutrition Labeling
• Shakur YA ,
• Tarasuk V ,
• O’Connor DL
• Briefel R ,
• US Preventive Services Task Force
• Jenkins DJA ,
• Spence JD ,
• Giovannucci EL ,
• Martí-Carvajal AJ ,
• Lathyris D ,
• CSPPT Investigators
• Buring JE ,
• Christen WG ,
• Manson JE ,
• VITAL Research Group
• Women’s Health Initiative Investigators
• Stewart AW ,
• Abdelhamid AS ,
• Brainard JS ,
• Kromhout D ,
• Omega-3 Treatment Trialists’ Collaboration
• Bassuk SS ,
• Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group
• Goodman GE ,
• Thornquist MD ,
• Thompson IM Jr . ,
• Tangen CM ,
• Sandler RS ,
• Polyp Prevention Study Group
• Vollset SE ,
• Lewington S ,
• B-Vitamin Treatment Trialists’ Collaboration
• Travers-Gustafson D ,
• Colmers IN ,
• Albert CM ,
• Van Denburgh M ,
• Pittas AG ,
• Dawson-Hughes B ,
• Sheehan P ,
• D2d Research Group
• Bennett D ,
• Billington EO ,
• Raymond DA ,
• Hanley DA ,
• Campbell PT ,
• Gapstur SM ,

We use cookies to enhance our website for you. Proceed if you agree to this policy or learn more about it.

• Essay Database >
• Essay Examples >
• Essays Topics >
• Essay on Dietary Supplements

Example Of Dietary Supplements Essay

Type of paper: Essay

Topic: Dietary Supplements , Heart , Business , Social Issues , Obesity , Health , Marketing , Products

Published: 01/26/2020

ORDER PAPER LIKE THIS

Dietary supplements are orally taken products that contain certain dietary ingredients as specified by the Dietary Supplement Health and Education Act that are intended to supplement diets that contain these ingredients (Dwyer et al, 2005). The products in this category exclude tobacco and are marketed in forms such as tablets and capsules. The ingredients include vitamins, minerals, herbs or other botanicals, amino acids, and other dietary substances and extracts. Dietary supplements have significant benefits to users. According to Dwyer et al (2005), a major benefit of dietary supplements is that they present an opportunity to individuals to improve their health in cases where they may be exposed to inadequate nutrient intake. This could be due to poverty, inappropriate food selection or depression. Dietary supplements are therefore important in achieving nutrient adequacy. Dietary supplements can also be used to stimulate weight loss. Although Dwyer et al (2005) observed that there is scanty scientific evidence on this claim; there are multiple supplements in the market aimed at stimulating weight loss. Dietary supplements are also useful to athletes and other individuals who engage in similar activities in improving performance besides general health. There are a number of risks associated with taking dietary supplements. The Food and Drug Administration (FDA) noted that they can interact with other medication that a person might be taking. For instance, calcium would interfere with certain heart medications if taken concurrently. Another risk related to dietary supplements regards the dosage. If taken in excess, a dosage can have serious side effects such as headaches and liver damage for the case of vitamin, or impaired muscle due to a buildup of calcium deposits. The government’s regulation of dietary supplements revolves around safety of the products before and even after they are introduced to the market rather than their effectiveness. Cite observed that the government does not approve these supplements on the basis of effectiveness, but only reviews new ingredients for safety prior to marketing through its agency, the FDA. The FDA can also ban products from the market if it determines that they are unsafe, have been adulterated or have misleading claims. DSHEA stipulates various regulatory guidelines on dietary supplements. Dietary supplements are used to treat and manage obesity in two different ways: they are used to provide important nutrients that may be absent in calorie-restricted diets; and they stimulate weight loss. Multiple dietary supplements are used for managing obesity (Dwyer et al, 2005). Bitter Orange has been widely marketed as a dietary supplement for weight loss. Bitter Orange contains chemicals that alter the functioning of organs in various ways. When taken, some of the components can increase blood pressure as well as the activity rate of some organs such as the heart. Consequently, the body uses more energy than in a normal condition. For this reason, Bitter Orange is used to treat obesity and manage weight by stimulating weight loss. Primarily, this dietary supplement contains synerphrine and the product’s daily recommended dosage is between 4-6 grams (Blumenthal, 2005, p. 4). There is little evidence on the efficacy of this dietary supplement in managing weight loss or treating obesity and equally scanty data regarding concerns that have been raised regarding the product (National Center for Complementary and Alternative Medicine, 2007). The fact that this product contains substances that speed up the heart rate and raise blood pressure renders it unsafe for use as dietary supplements.

Blumenthal, M. (2005). Bitter Orange Peel and Synerphrine. American Botanical Council. Dwyer, T. J., Allison, B. D. & Coates, M. P. (2005). Dietary Supplements in Weight Reduction. Journal of the American Dietetic Association, 105(5): 80-86. Retrieved from http://www.sciencedirect.com.proxyau.wrlc.org/science/article/pii/S0002822305002889# Food and Drug Administration. (2012). Dietary Supplements: What You Need to Know. Retrieved from http://www.fda.gov/Food/ResourcesForYOu/Consumers/ucm109760.htm National Center for Complementary and Alternative Medicine. (2007) Bitter Orange. Retrieved from http://nccam.nih.gov/health/bitterorange

Cite this page

Share with friends using:

Removal Request

Finished papers: 1584

This paper is created by writer with

ID 270496217

If you want your paper to be:

Well-researched, fact-checked, and accurate

Original, fresh, based on current data

Eloquently written and immaculately formatted

275 words = 1 page double-spaced

Get your papers done by pros!

Other Pages

Grudges essays, furnishes essays, ginnet essays, ecpa essays, expectance essays, guardsmen essays, fromberg essays, fishhooks essays, frisks essays, felts essays, stargazing essays, naked eye essays, mesomorphic essays, fillipo essays, gi tract essays, schnorr essays, chillingworth essays, literacy samples article example, early child development presentation, performance management at the national institute of management presentation example, free presentation on operational plan, social responsibility articles examples, sample presentation on bible in context, example of managing speech anxiety presentation, program director application letters examples, good the third phase of business ethics article example, good article about mediated communication, free criteria for evaluating qualitative research article example, the colonial stereotype presentation, good example of employee turnover presentation, good example of article on two approaches to relieving poverty, sample presentation on neurofeedback training from the prefrontal cortex enhances cognitive functions, marketing is everybodys business article samples, love exemplar essay to follow, human population type to use as a writing model, write by example of this mass extinction assignment 5 essay, mood disorders essay sample, good example of essay on understanding null, good research paper on diverse and global workforce, good essay about operational and classical conditioning, free you cant be neutral on a moving train essay top quality sample to follow, write by example of this quantitative research design essay, should electronic dance music festivals be banned a sample essay for inspiration mimicking.

Password recovery email has been sent to [email protected]

Use your new password to log in

You are not register!

By clicking Register, you agree to our Terms of Service and that you have read our Privacy Policy .

Now you can download documents directly to your device!

Check your email! An email with your password has already been sent to you! Now you can download documents directly to your device.

or Use the QR code to Save this Paper to Your Phone

The sample is NOT original!

Short on a deadline?

Don't waste time. Get help with 11% off using code - GETWOWED

No, thanks! I'm fine with missing my deadline

• U.S. Department of Health & Human Services HHS
• National Institutes of Health NIH
• Division of Program Coordination, Planning, and Strategic Initiatives DPCPSI

Dietary Supplements: What You Need to Know

Many adults and children in the United States take one or more vitamins or other dietary supplements . In addition to vitamins, dietary supplements can contain minerals , herbs or other botanicals , amino acids , enzymes , and many other ingredients . Dietary supplements come in a variety of forms, including tablets, capsules , gummies, and powders as well as drinks and energy bars. Popular supplements include vitamins D and B12; minerals like calcium and iron ; herbs such as echinacea and garlic; and products like glucosamine , probiotics, and fish oils.

The Dietary Supplement Label

Products sold as dietary supplements come with a Supplement Facts label that lists the active ingredients, the amount per serving ( dose ), and other ingredients, such as fillers , binders , and flavorings. The manufacturer suggests the serving size, but your health care provider might decide a different amount is more appropriate for you.

Effectiveness

Some dietary supplements can improve overall health and help manage some health conditions. For example: 

• Calcium and vitamin D help keep bones strong and reduce bone loss. 
• Folic acid decreases the risk of certain birth defects.
• Omega-3 fatty acids from fish oils might help some people with heart disease. 
• A combination of vitamins C and E, zinc , copper , lutein , and zeaxanthin (known as an Age-Related Eye Disease Study [AREDS] formula) may slow down further vision loss in people with age-related macular degeneration (AMD). 

Many other supplements need more study to determine if they have value. The U.S. Food and Drug Administration (FDA) does not determine whether dietary supplements are effective before they are marketed.

Safety and Risk

Many supplements contain active ingredients that can have strong effects on the body. Always be alert to the possibility of a bad reaction, especially when taking a new product.

You are most likely to have side effects from dietary supplements if you take them at high doses, or instead of prescribed medicines, or if you take many different supplements. Some supplements can increase the risk of bleeding or, if taken before surgery, can change your response to anesthesia. Supplements can also interact with some medicines in ways that might cause problems. Here are a few examples:

• Vitamin K can reduce the ability of the blood thinner warfarin to prevent blood from clotting.
• St. John’s wort can speed the breakdown of many medicines and reduce their effectiveness (including some antidepressants, birth control pills, heart medications, anti-HIV medications, and transplant drugs ).
• Antioxidant supplements, such as vitamins C and E, might reduce the effectiveness of some types of cancer chemotherapy .

Manufacturers may add vitamins, minerals, and other supplement ingredients to foods you eat, especially breakfast cereals and beverages. As a result, you may get more of these ingredients than you think, and more might not be better. Taking more than you need costs more and might also raise your risk of side effects. For example, too much vitamin A can cause headaches and liver damage, reduce bone strength, and cause birth defects. Excess iron causes nausea and vomiting and may damage the liver and other organs.

Be cautious about taking dietary supplements, beyond a standard prenatal supplement, if you are pregnant or nursing . Also, be careful about giving supplements to a child, unless recommended by their health care provider. Many supplements have not been well tested for safety in children and in those who are pregnant or nursing.

FDA has established Good Manufacturing Practices (GMPs) that companies must follow to help ensure the identity, purity, strength, and composition of their dietary supplements. These GMPs can prevent adding the wrong ingredient (or too much or too little of the correct ingredient) and reduce the chance of contamination or improper packaging and labeling of a product. FDA periodically inspects facilities that manufacture supplements.

Several independent organizations offer quality testing and allow products that pass these tests to display a seal of quality assurance that indicates the product was properly manufactured, contains the ingredients listed on the label, and does not contain harmful levels of contaminants. These seals do not guarantee that a product is safe or effective. Organizations that offer quality testing include:*

• ConsumerLab.com
• NSF International
• U.S. Pharmacopeia

      * Any mention of a specific company, organization, or service does not represent an endorsement by ODS .

Talk with Your Health Care Providers

Tell your health care providers (including doctors, dentists,  pharmacists , and dietitians) about any dietary supplements you’re taking. They can help you determine which supplements, if any, might be valuable for you.

Keep a complete record of any dietary supplements and medicines you take. The Office of Dietary Supplements website has a useful form, My Dietary Supplement and Medicine Record , that you can print and fill out at home. For each product, note the name, the dose you take, how often you take it, and the reason for use. You can share this record with your health care providers to discuss what’s best for your overall health. 

Keep in Mind

• Consult your health care provider before taking dietary supplements to treat a health condition.
• Get your health care provider’s approval before taking dietary supplements in place of, or in combination with, prescribed medicines.
• If you are scheduled to have any type of surgical procedure, talk with your health care provider about any supplements you take. 
• Keep in mind the term natural doesn’t always mean safe. Some all-natural botanical products, for example comfrey and kava , can harm the liver. A dietary supplement’s safety depends on many things, such as its chemical makeup, how it works in the body, how it is prepared, and the amount you take. 
• What are its potential benefits for me?
• Does it have any safety risks?
• What is the proper dose to take?
• How, when, and for how long should I take it? 

Federal Regulation of Dietary Supplements

Dietary supplements are products intended to supplement the diet. They are not medicines and are not intended to treat, diagnose , mitigate , prevent, or cure diseases. FDA is the federal agency that oversees both supplements and medicines, but FDA regulations for dietary supplements are different from those for prescription or over-the-counter medicines.

Medicines must be approved by FDA before they can be sold or marketed. Supplements do not require this approval. Supplement companies are responsible for having evidence that their products are safe, and the label claims are truthful and not misleading. However, as long as the product does not contain a new dietary ingredient (one introduced since October 15, 1994), the company does not have to provide this safety evidence to FDA before the product is marketed.

Dietary supplement labels may include certain types of health-related claims. Manufacturers are permitted to say, for example, that a supplement promotes health or supports a body part or function (like heart health or the immune system). These claims must be followed by the words, “This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.”

Manufacturers must follow GMPs to ensure the identity, purity, strength, and composition of their products. If FDA finds a dietary supplement to be unsafe, it may remove the product from the marketplace or ask the manufacturer to voluntarily recall the product.

FDA monitors the marketplace for potential illegal products that may be unsafe or make false or misleading claims. The Federal Trade Commission , which monitors product advertising, also requires information about a supplement product to be truthful and not misleading.

The federal government can take legal action against companies and websites that sell dietary supplements when the companies make false or deceptive statements about their products, if they promote them as treatments or cures for diseases, or if their products are unsafe.

Federal Government Information Sources on Dietary Supplements

National institutes of health.

National Institutes of Health ( NIH ) supports research and provides educational materials on dietary supplements.

• Office of Dietary Supplements (ODS) ODS provides accurate and up-to-date scientific information about dietary supplements.
• National Center for Complementary and Integrative Health (NCCIH) NCCIH also has scientific information about dietary supplement ingredients.
• NIH Health Information   Information about healthy living and wellness from across NIH.

U.S. Food and Drug Administration 

Federal trade commission (ftc), u.s. department of agriculture (usda), u.s. department of health and human services (hhs).

This fact sheet by the National Institutes of Health (NIH) Office of Dietary Supplements (ODS) provides information that should not take the place of medical advice. We encourage you to talk to your health care providers (doctor, registered dietitian, pharmacist, etc.) about your interest in, questions about, or use of dietary supplements and what may be best for your overall health. Any mention in this publication of a specific product or service, or recommendation from an organization or professional society, does not represent an endorsement by ODS of that product, service, or expert advice.

Updated: January 4, 2023 History of changes to this fact sheet

• Weight Management
• Nutrition Facts
• Nutrition Basics
• Meal Delivery Services
• Fitness Gear
• Apparel & Accessories
• Recipe Nutrition Calculator
• Weight Loss Calorie Goal
• BMI Calculator
• Body Fat Percentage Calculator
• Calories Burned by Activity
• Daily Calories Burned
• Pace Calculator
• Editorial Process
• Meet Our Review Board
• Benefits and Risks
• Who May Benefit
• Purchasing Tips
• Which To Take
• What To Skip
• What To Buy

Benefits and Risks of Dietary Supplements

Shereen Lehman, MS, is a former writer for Verywell Fit and Reuters Health. She's a healthcare journalist who writes about healthy eating and offers evidence-based advice for regular people.

Elena Klimenko, MD, is a board-certified doctor in internal medicine and is licensed in medical acupuncture and homeopathy.

Potential Problems

• Next in Supplements Guide Why Aren't Dietary Supplements Regulated?

Dietary supplements are products designed to augment your daily intake of nutrients, including vitamins and minerals. Many are safe and offer significant health benefits, but there are some that pose health risks, especially if overused. Dietary supplements include amino acids, fatty acids, enzymes,  probiotics , herbals, botanicals, and animal extracts.

In addition to vitamins and essential minerals , popular supplements include:

• Chondroitin
• Glucosamine
• St. John’s wort
• Saw palmetto

Normally, most people should be able to get all the nutrients they need from a balanced diet . However, supplements can provide you with extra nutrients when your diet is lacking or certain health conditions (such as cancer, diabetes, or chronic diarrhea) trigger a deficiency. Supplements for runners , for example, can provide certain nutrients that can be harder to get enough of on a plant-based diet.

In most cases, a multivitamin/mineral supplement will provide all the micronutrients your body needs. They are generally safe because they contain only small amounts of each nutrient (as measured by the daily value , or DV).

Individual nutrients are available as supplements, usually in doses larger than your typical multivitamin. They can be used to treat a deficiency, such as an iron deficiency, or reduce the risk of a medical condition, such as hypertension. ​

For example, large doses of vitamin B3 (niacin) may help raise "good" high-density lipoprotein (HDL) cholesterol, while folic acid has long been used to reduce the risk of a birth defect called spina bifida. Antioxidants, such as vitamin C and vitamin E, may reduce the toxic effect of chemotherapy drugs (allowing patients to tolerate larger doses of chemo). Turmeric supplements can be helpful for those with inflammation-related conditions.

Unless a specific deficiency is identified, a supplement is usually not necessary if you eat and exercise properly. When it comes to vitamins for women , specific formulations are often recommended for certain stages of life, such as childbearing years and menopause. The appropriate use of supplements can help you avoid side effects and toxicities associated with overuse.

In the United States, dietary supplements are not regulated as strictly as pharmaceutical drugs. Manufacturers do not have to prove that they are either safe or effective. The U.S. Food and Drug Administration (FDA) doesn't even determine whether dietary supplements are effective before they are shipped to market shelves.

The FDA does maintain a list of tainted or potentially harmful products marketed as dietary supplements. The worst offenders are usually weight loss aids, "natural" sexual enhancement pills , and supplements targeted at bodybuilders.

Supplement manufacturers have to follow certain labeling guidelines, including what they can say and not about the purported benefits. That doesn't stop manufacturers from claiming, often misleadingly, that their product can "boost the immune system" or "treat arthritis" even if there is little scientific evidence to support the claims. Generally speaking, the FDA only acts on the most serious infractions.

Large doses of certain nutrients can have adverse effects. You can even overdose on certain supplements, risking serious harm and death. Among some of the harmful interactions or dosing concerns:

• Vitamin K can reduce the effectiveness of blood thinners like Coumadin (warfarin).
• Vitamin E can increase the action of blood thinners, leading to easy bruising and nosebleeds.
• St. John’s wort can accelerate the breakdown of many drugs, including antidepressants and birth control pills, thereby reducing their effectiveness.
• Vitamin B6 (pyridoxine), when used for a year or more at high doses, can cause severe nerve damage. Vitamin B6 can also reduce the effectiveness of the anti-seizure drug Dilantin (phenytoin) and levodopa (used to treat Parkinson's disease). 
• Vitamin A used with retinoid acne medications such as Accutane (isotretinoin) and Soriatane (acitretin) can cause vitamin A toxicity.
• Iron and calcium supplements can reduce the effectiveness of antibiotics, namely tetracyclines and fluoroquinolones, by as much as 40%.
• Vitamin C can cause diarrhea when taken in doses higher than the gut can absorb (but some patients can tolerate 5,000mg to 25,000mg per day).
• Selenium , boron, and iron supplements can be toxic if taken in large amounts.

Speak with a healthcare provider about any supplements you plan to take as well as any medications you are currently taking, whether they be pharmaceutical, over-the-counter, herbal, traditional, or homeopathic.

For the utmost safety and quality, choose supplements tested and approved by a certifying body such as the U.S. Pharmacopeia (USP). Never use expired supplements .

U.S. Food and Drug Administration. Tips for older dietary supplement users .

Afolayan AJ, Wintola OA. Dietary supplements in the management of hypertension and diabetes - a review .  Afr J Tradit Complement Altern Med . 2014;11(3):248-258. doi:10.4314/ajtcam.v11i3.35

National Institutes of Health Office of Dietary Supplements. Niacin fact sheet for health professionals .

Centers for Disease Control and Prevention. Folic acid helps prevent some birth defects .

Singh K, Bhori M, Kasu YA, Bhat G, Marar T. Antioxidants as precision weapons in war against cancer chemotherapy induced toxicity: Exploring the armoury of obscurity . Saudi Pharm J . 2018;26(2):177-190. doi:10.1016/j.jsps.2017.12.013

U.S. Food and Drug Administration. Tainted products marketed as dietary supplements .

U.S. Food and Drug Administration. Center for Biologics Evaluation and Research 2003 .

U.S. Food and Drug Administration. Fortify your knowledge about vitamins .

National Institutes of Health Office of Dietary Supplements. Dietary supplements: What you need to know .

Sulli MM. Ezzo D. Drug interactions with vitamins and minerals . US Pharm. 2007;1:42-55. 

By Shereen Lehman, MS Shereen Lehman, MS, is a former writer for Verywell Fit and Reuters Health. She's a healthcare journalist who writes about healthy eating and offers evidence-based advice for regular people.

Click through the PLOS taxonomy to find articles in your field.

For more information about PLOS Subject Areas, click here .

Loading metrics

Open Access

Peer-reviewed

Research Article

The impact of nutritional supplement intake on diet behavior and obesity outcomes

Contributed equally to this work with: Sven Anders, Christiane Schroeter

Roles Data curation, Formal analysis, Methodology, Software, Writing – review & editing

* E-mail: [email protected]

Affiliation Department of Resource Economics and Environmental Sociology, University of Alberta, Edmonton, Canada

Roles Conceptualization, Investigation, Writing – original draft

Affiliation Agribusiness Department, California Polytechnic State University, San Luis Obispo, California, United States of America

• Sven Anders, 
• Christiane Schroeter

• Published: October 9, 2017
• https://doi.org/10.1371/journal.pone.0185258
• Reader Comments

After decades-old efforts to nudge consumers towards healthier lifestyles through dietary guidelines, diet-related diseases are on the rise. In addition, a growing share of U.S. consumers proactively chooses nutritional supplements as an alternative preventative way of maintaining good health, a $25.5 billion industry in the United States. This paper investigates possible linkages between the economics of consumer supplement choices and the relationship to important dietary and health outcomes. We use National Health and Nutrition Examination Survey (NHANES) data to estimate the impact of nutritional supplements intake on respondent’s body weight outcomes, controlling for diet quality.: The focus of this article is to determine whether nutritional supplements takers differ from non-takers with regard to their health outcomes when controlling for differences in diet quality, based on individual Healthy Eating Index (HEI-2010) score. The analysis applies treatment effects estimators that account for the selection bias and endogeneity of self-reported behavior and diet-health outcomes. The analysis demonstrates a negative association between supplement intake and BMI but no significant effect on an individual’s diet quality. Our findings suggest that individuals proactively invest into their health by taking nutritional supplements instead of improving diet quality through more nutritious food choices. Our results provide important contributions to the literature on a key food policy issue. Knowledge of the determinants of supplement demand in the context of strong diet-health trends should also be helpful to stakeholders in the U.S. produce sector in their competition over consumer market share.

Citation: Anders S, Schroeter C (2017) The impact of nutritional supplement intake on diet behavior and obesity outcomes. PLoS ONE 12(10): e0185258. https://doi.org/10.1371/journal.pone.0185258

Editor: Frank Wieringa, Institut de recherche pour le developpement, FRANCE

Received: January 17, 2017; Accepted: September 8, 2017; Published: October 9, 2017

Copyright: © 2017 Anders, Schroeter. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: The data the authors used stem from the U.S. NHANES database ( https://wwwn.cdc.gov/nchs/nhanes/ContinuousNhanes/Default.aspx?BeginYear=2007 ). The authors used a sample of adult population from the 2007/08 NHANES data that provides the necessary features for their analysis.

Funding: The authors received no specific funding for this work.

Competing interests: The authors have declared that no competing interests exists.

Introduction

Despite the proven health benefits of a diet rich in fruits and vegetables [ 1 – 6 ], the average U.S. adult only consumes 64% of the vegetable servings and half of the fruit servings recommended by the 2010 Dietary Guidelines for Americans (DGAs) (U.S. Department of Agriculture and U.S. Department of Health and Human Services [ 7 ]. At the same time, the consumption of solid fats, alcohol, and added sugars (SoFAAS) is 2- to 3-fold of their recommended limits [ 8 ]. The nutrient deficit from a reduced consumption of fruit and vegetables stands against the widespread intake of nutritional supplements with 62% of U.S. adults reporting to consume supplements at least occasionally and 46% are reported to take supplements regularly [ 9 ]. We solely focus on individual supplementation with nutrients vs. food fortification. Sales of dietary supplements are valued at $25.6 billion in the U.S. and form an area of strong growth and competition for the U.S. produce industry. Population ageing, retiring baby boomers and rising awareness of diet-health related disease (e.g. obesity, diabetes) are driving forces behind the expansion of preventative consumption of dietary supplements as a proactive way of maintaining good health [ 10 ]. Each year, preventative health care could save up to $43 billion, which encompasses direct medical costs and lost productivity resulting from secondary chronic health problems [ 11 ].

However, while the interplay of appropriate food choices, nutrient intakes and physical exercise in consumer health behavior and outcomes [ 12 – 14 ] is well documented, little is known about the role and impact of nutritional supplements as an input into consumer diet quality and health status. The 2010 DGAs state that nutrients should come primarily from food, and recommends that specific supplementation might be needed for at-risk populations, such as postpartum women, as well as older Americans [ 7 ]. However, evidence suggests that the intake of nutritional supplements may be unnecessary and potentially even be detrimental to human health [ 15 – 16 ]. As such, the 2015 Dietary Guidelines Advisory Committee (DGAC) emphasizes that healthy dietary patterns are to be achieved through recommended food and beverage choices rather than with nutritional supplements except as needed for at-risk populations [ 17 ]. These inconsistencies highlight the need for research that expands the understanding of the role of nutritional supplements in U.S. consumer’s diet-health behavior and whether supplements are currently replacing or supplementing a healthy diet. Consumers may not have access to complete information about the costs and benefits of supplements and their potential effects on diet quality and personal health [ 18 ].

This article provides an important research contribution by estimating the relationship between health behavior and its potential linkage to dietary quality outcome measures, utilizing the case of nutritional supplements intake. Our objectives are to identify and quantify (1) determinants of nutritional supplements intake decisions (2) whether and to what extent supplement takers and non-takers differ with regard to diet-health outcomes (e.g. Body Mass Index (BMI)) when differences in diet quality (as measured by the Healthy Eating Index (HEI) are controlled for, and (3) whether and to what extent supplement takers and non-takers differ in diet quality (HEI) outcomes when differences in BMI are controlled for.

Previous studies acknowledge the interdependence of health behavior, dietary choices and health outcomes in terms of their short- and long-term public health impacts [ 19 – 23 ]. However, apart from a few exemptions [ 24 – 25 ] the literature on diet-health and behavior typically neglects to incorporate explicit measures of diet or health or does not account for the possible endogeneity of the determinants of behavior. A common limitation is that key determinants of diet-health behavior such as socio-economic factors and unobserved heterogeneity may simultaneously influence individuals’ behavior and the stock of diet-health. Consequently, empirical estimates of behavior and the effects of exogenous factors will be biased, potentially leading to misguided policy conclusions. Such bias can be avoided by treating direct measures of diet-health behavior as endogenous determinants of health outcomes and by adopting appropriate modelling procedures to avoid this endogeneity bias and related measurement error.

The analysis in this article builds on [ 22 ], to our knowledge the only study that incorporates health indicators and other lifestyle variables into the study of nutritional supplements intake and food quality. We expand on this topic using a more recent dataset from the 2007–2008 NHANES and updated 2010 Healthy Eating Index (HEI-2010) scores. To overcome the issues of endogeneity and measurement error resulting from the possible self-selection bias in the NHANES data, our approach employs propensity score matching (PSM) estimators to determine the possible link between nutritional supplements intake, food quality and obesity outcomes. Nutritional supplements intake does not directly affect the BMI, yet, it might impact food quality choices, which may in turn influence the BMI.

PSM has emerged as a popular approach in the estimation of causal treatment effects in economic analyses. Given the reliance of the diet-health behavioral literature on cross-sectional observational data, such as NHANES, the analysis of treatment effects is often complicated by non-linear relationships and limited dependent outcome variables that are possibly endogenous. Compared against established analytical techniques including fixed effects models [ 26 ], Heckman-type switching regression modeling [ 27 ], and difference-in-difference estimators [ 28 ], PSM methods have been shown to be superior in eliminating the biases resulting from endogenous determinants and self-selection in ensuring the comparability of different groups in the process of outcome evaluations [ 29 – 30 ].

From a policy standpoint, it is important to understand what factors drive consumers’ compliance with nutritional recommendations [ 23 ] and what factors might impact an individual’s decision to consume nutritional supplements as likely substitutes in meeting specific diet quality and health outcomes. Results from our study will help to develop a better understanding of the factors that affect nutritional supplements intake as an input into the development of more efficient and effective promotional strategies for healthy food choices and targeted consumer health education.

Methodology

Economists have long been interested in the study of the interdependencies between dietary choices, nutrition and health outcomes in terms of their short- and long-term impacts on diet patterns and public health outcomes [ 31 ]. Becker’s model of investment in human capital [ 32 ] and Grossman’s seminal work on health capital [ 33 – 34 ] formalize the process by which individuals are endowed with a certain stock of health that deteriorates over a person’s lifetime [ 35 – 37 ]. The deterioration speed of a person’s health status depends, among other things, on investments in health through certain health behaviors.

A diet that follows the recommendations of the 2010 DGAs could be considered as an investment into an individual’s health stock and consuming the recommended amount of fresh fruits and vegetables as an investment in health. If an individual substitutes or complements the fruit and vegetable intake with nutritional supplements, the latter would constitute a similar investment in health capital, given that supplements may contribute to the overall utility derived from good health. Consumption choices such as smoking, alcohol intake, lack of exercise, and poor dietary patterns could accelerate the depletion rate of a person’s health stock. The depletion of the health stock beyond a certain threshold is associated with a higher probability of early death.

There are many intertemporal utility functions that could serve as a theoretical model for our analysis, such as the one developed by [ 33 – 34 ]. The empirical analyzes of individual’s diet behavior in the context of specific health outcomes is typically complicated by potential endogeneity between key variables of interest and a measurement error resulting from self-selection bias, which is an issue often encountered in consumer survey studies. Due to potential misspecification errors, the use of ordinary least squares estimators (OLS) may lead to biased results [ 38 ]. Instrumental variable estimators (IV) form a common econometric solution to minimize endogeneity. However, their application is often constrained by the availability of suitable instruments [ 39 ].

In this study, the nature of the NHANES data and the specific research questions make it even more difficult to find suitable instruments. For these reasons, common IV approaches are deemed less suitable. PSM, originally developed by Rosenbaum and Rubin (1983), has enjoyed increasing popularity in empirical studies of situations where the effect and outcome of a specific treatment is of interest [ 25 , 40 – 41 ]. In the economics literature, PSM has been employed to determine the effects of labor market and training courses on individual’s wage earnings [ 42 – 44 ]. In health economics and food consumption studies, PSM methods have been utilized to analyze how consumers that were exposed to a particular treatment (e.g. food label usage) differed from those who reportedly did not receive the same treatment [ 25 , 45 – 46 ]. In our study, PSM will account for the potential selection bias of the self-reported nutritional supplements intake and possible endogeneity of the supplement intake in the treatment outcome variable.

Theoretical model

Y(1) and Y(0) are the two possible outcomes with and without supplement intake. The parameter of interest is the average treatment effect on the treated (ATT), because it gives the difference between expected outcome values of supplement takers and non-takers. Estimating the average treatment effect on the treated is only possible under certain assumptions, because the counterfactual is not observed. Several assumptions need to hold in order to obtain reliable treatment effects using PSM.

The next assumption is usually referred to as ‘unconfoundedness’ or ‘conditional independence’ assumption (CIA) [ 41 , 49 – 50 ].

This assumption ensures that individuals with the same characteristics X (e.g. income level) are assumed to have an equal chance of being part of the treatment or control group. Once the above assumptions are satisfied, the propensity score of the ATT can then be estimated reliably. To further validate whether our selections models meet the assumption of conditional independence, in other words, whether and to what extend unobserved variables in the treatment selection model may bias the estimates of subsequent treatment effects we perform Rosenbaum bounds tests [ 51 ]. The bounds test statistics allows us to assess the strength unmeasured or unobserved selection variables must have in order that the estimated treatment effects from propensity score matching would have resulted from a purely non-random assignment [ 52 ].

Empirical models

The analysis in this article employs data from the 2007–2008 National Health and Nutrition Examination Survey (NHANES) (Centers for Disease Control and Prevention [ 48 ]. The NHANES is the primary national survey used to assess the health and nutritional status of the U.S. population. Participants in the NHANES are randomly selected civilian residents of the United States. The survey is divided into the physical examination, questionnaire and personal interview components. The interview is used to gather information on demographic, socioeconomic, nutritional, and health related issues. The physical examination component is generally used to conduct laboratory investigations [ 48 ].

Data from various NHANES survey cycles has been used in a number of similar studies focused on individual’s health behavior, food consumption choices, and a multitude of other economic and non-economic research questions [ 16 , 19 – 22 , 53 – 54 ]. For the purposes of the analysis in this article, only adult NHANES participants of at least 20 years were selected, as this sample typically makes their own food, diet or health behavioral (e.g. nutritional supplements intake) decisions.

The Healthy Eating Index ( HEI ) is a tool used to measure the diets of Americans against the DGAs. The HEI is composed of twelve sub-components such as HEI Total Fruits, HEI Total Vegetables, HEI Greens & Beans, which carry individual scores that add up to hundred to give the Total HEI. A higher HEI score indicates a diet of higher quality. Using the code written by [ 54 ], we computed the Healthy Eating Index-2010 (HEI-2010) for all NHANES participants in our sample. A negative relationship between nutritional supplements intake and BMI outcomes has been documented in previous research and is of particular to food policy [ 21 ].

With regard to the variables Diabetes and Blood Pressure, previous literature shows a controversial relationship between these health conditions and nutritional supplements intake. Some reports show no association while others have documented a negative impact [ 19 , 55 – 57 ].

Based on previous research, we expect supplement intake to be positively associated with education, income, female, age and white [ 21 , 58 – 61 ]. Lifestyle factors such as smoking, alcohol intake are expected to have a negative relationship with nutritional supplements intake [ 21 , 59 , 62 ]. In contrast, those following an active lifestyle (e.g. very active) are assumed to be more likely to consider supplements as part of their health behavioural choices. We anticipate that food stamps recipients might form an at-risk population and may need supplements to boost their diet quality.

An ad-hoc approach to the matching of individuals in order to achieve an optimal balancing of pre-treatment characteristics is unfeasible [ 41 ]. Instead, our selection of variables in building the propensity score model in Eq (8) is guided by economic theory and a sound assessment of previous relevant research. Accordingly, our first step of analysis involves the estimation of Eq (8) to achieve the critical identification assumption of unconfoundedness (CIA), a necessary step for the unbiased estimation of treatment effects. The resulting balancing of covariate variables between treatment and control group members is then conveniently expressed in an individual’s propensity score as a single-index variable input into the second-stage matching procedure. Matching algorithms commonly applied in PSM studies are: Nearest Neighbor, Caliper (Radius), Stratification and Kernel matching algorithms. The estimation of propensity scores and matching algorithms is performed using the psmatch2 package in Stata [ 63 ].

A key feature of the propensity score matching approach is its ability to reduce the self-selection bias and resulting measurement error in treatment effects. In order to validate the quality of matching between nutritional supplements takers and the counterfactual group of non-takers, we perform Rosenbaum’s (1991) [ 64 ] standard bias test (see S2 Table supporting information). By comparing the difference of the sample means in the treated and matched control sub-samples for each covariate (see S3 Table supporting information), expressed as a percentage of the square root of the average of the sample variances in both groups, the test allows us to quantify the reduction in selection bias and the quality of the chosen covariate in the propensity score model. Examining the t-test results of unmatched and matched covariates reveals insignificant differences in the matched samples after the propensity score estimation. We also evaluate minor changes in our model specification. Our results are largely insensitive to alternative variables, with the visible exemptions of a few variables (e.g. HEI-Dairy). Overall, the results on matching quality imply that our propensity score specification is reliable and robust. Both propensity score models satisfy the balancing hypothesis (common support), allowing us to test whether nutritional supplement generate significant differences in our selected diet quality and obesity outcomes. In addition, S2 Table presents the mean value of the standard bias measure across the different matching algorithms. For the impact of supplement on NHANES participants BMI the mean standard bias before matching is roughly 12%. PSM is able to reduce this bias significantly for all matching algorithms to levels between 1.2% and 2.7%; a range generally considered reliable [ 41 ].

The focus of this article is to determine whether nutritional supplements takers differ from non-takers with regard to their health outcomes when controlling for differences in diet quality. Supplements are assumed to contribute to an individual’s utility derived from good health and are inputs to the person’s health production function. The factors associated with diet-health behavior and specifically nutritional supplements intake decisions are diet quality, health indicators, demographics, and lifestyle. In order to identify and quantify the determinants of supplement intake decisions, the PSM model in ( 8 ) was estimated to match all the respondents on a wide range of variables. Table 1 shows the factors associated with the selection into the treatment group of supplement takers.

• PPT PowerPoint slide
• PNG larger image
• TIFF original image

https://doi.org/10.1371/journal.pone.0185258.t001

Table 2 indicates no relationship between health indicator variables and nutritional supplements intake. Previous literature shows mixed results with regard to supplement intake and the presence of a health condition like diabetes or high blood pressure. While some of the studies report that there is a negative relationship between supplement intake and diabetes and blood pressure [ 56 – 57 ], others conclude that there is no association between supplement intake and these conditions [ 19 , 55 ]. In addition, we found no association between selection into the nutritional supplements intake group and all the components of the HEI-2010.

https://doi.org/10.1371/journal.pone.0185258.t002

Table 2 shows that with the exception of marital status and high school, all of the demographic factors are significant at explaining the probability of being selected into the treatment group. Demographic factors that positively affect the probability of taking nutritional supplements are age , ethnicity , a higher level of education , and a higher household income . These results conform to previous research [ 21 , 53 , 59 – 61 , 65 ]. We find that males are 59% less likely to take nutritional supplements compared to their female counterparts. This finding confirms the results of previous studies [ 21 , 59 , 62 , 65 ]. The negative relationship between male and supplement intake suggests that females might be more concerned about diet behavior. Our findings suggest that ethnic heritage seems to play an important role in determining selection into the treatment group. In comparison to African American individuals, individuals of other races are more likely take nutritional supplements.

The negative effect of household size on nutritional supplements intake suggests that members of larger households may not consume supplements, given budgetary constraints [ 62 ]. Consumers who completed a higher level of education may be in a more informed position to take control of their health. Participants who fall in the highest income group, often correlated with higher educational attainment have the greatest propensity (69%) to take supplements, which confirms an income and educational gradient in that nutritional supplements intake decisions reported in previous studies [ 47 , 65 ].

Our results for the lifestyle category show that food stamp recipients are 22% less likely to take nutritional supplements compared to other respondents. Food stamps may not be used for the purchase of vitamins and supplements [ 66 ]. Our result suggests that nutritional supplements are not consumed by one important target group of at-risk consumers who may be in need of complementary supplementation with nutrients.

As has been commonly found in previous related literature [ 22 , 57 , 62 , 65 , 67 – 69 ], smokers are 17% less likely to take nutritional supplements as compared to non-smokers. This negative relationship may indicate that smokers are less concerned about their health. Our explanation for the sign change in the smoker variable indicates that smokers tend to be less concerned about their health. However, Table 2 shows that smokers who take supplements tend to have lower BMIs. This confirms the findings of previous research that shows that smokers tend to have lower BMIs on average, compared to non-smoking population. Using NHANES data from the same time frame, Plurphanswat and Rodu (2014) [ 70 ] show that both male and female smokers are more likely to be underweight and normal weight compared to never smokers. We did not find any significant relationship between the heightened consumption of alcohol and taking nutritional supplements. Previous research shows that the health impact of alcohol on diet quality is ambiguous [ 71 ].

Individuals who exhibited active lifestyles are 49% more likely to take nutritional supplements. This is consistent with findings from previous literature [ 20 , 55 , 57 , 62 , 65 , 69 , 72 – 73 ].

Analyzing health outcomes of nutritional supplements consumers

In order to deepen the PSM analysis, we used different matching algorithms to build on the estimated PSM model in order to determine whether regular consumers of nutritional supplements may display improved health outcomes, as measured by their BMI. Thus, we aimed at quantifying whether and to what extent supplement takers and non-takers differ in BMI outcomes when variations in diet quality (HEI) are controlled for. We used the factors discussed in Table 1 to determine the selection into the treatment group. Table 3 shows the average ATTs applying different matching algorithms for the comparison of respondents in the nutritional supplements treatment group versus the control group.

https://doi.org/10.1371/journal.pone.0185258.t003

The results in Table 3 show a clear distinction between nutritional supplements takers and non-takers in terms of their BMI. Our results suggest that the individual HEI components do not have a significant impact on supplement intake. Despite this lack of significance, there exists a relationship between supplement intake and total HEI and thus, BMI. The consistent outcome across all the matching algorithms is worth noting: Across the select matching algorithms, supplement takers have a lower BMI of more than 1 kg/(body height in m). 2

The significant difference in BMI between nutritional supplements takers and non-takers is striking, because the components of the HEI-2010 did not have a significant effect on the selection into the treatment group. Our results expand the findings of previous studies that have found inconclusive results [ 25 ]. According to Kimmons et al. [ 74 ] individuals who are obese or overweight are less likely to take nutritional supplements. Balluz et al. [ 19 ] note that those who are overweight or obese may have a greater tendency to take supplements because they may be making weight loss attempts or are on a special diet that may include nutritional supplements.

Nutritional supplements intake and diet quality

In order to quantify whether and to what extent supplement takers and non-takers differ in diet quality (HEI) outcomes when differences in BMI are controlled for, we repeated the matching procedure while controlling for differences in BMI. Table 1 shows the determinants for selection into the treatment group of nutritional supplements taker. In addition to using the variables presented in Table 1 , we added the variables BMI and some college into our model.

The introduction of another education variable resulted in all of the education variables becoming significant at explaining the selection into the treatment of group of being a nutritional supplements taker. BMI has a significant negative relationship on selection into the treatment group. Previous research has documented the negative relationship between BMI and nutritional supplements intake [ 21 , 60 , 62 , 67 , 69 , 72 – 75 ].

We calculated ATTs to determine whether significant differences exist between supplement takers and non-takers in terms of HEI. Furthermore, we selected three sub-component scores of the HEI-2010 ( HEI Total , HEI Total Vegetables and HEI Total Fruits ) due to the known relationship between fruit and vegetables intake and obesity. Table 4 shows the results of the various matching algorithms.

https://doi.org/10.1371/journal.pone.0185258.t004

For the nearest Neighbor matching method and stratification matching, we find a significant positive relationship between HEI total and nutritional supplements intake confirming previous results by Schroeter, Anders, and Carlson [ 22 ] and Kennedy [ 76 ]. Table 4 also shows a higher score of HEI Total Fruit for supplement consumers However, while both results indicate that supplement consumers have overall higher diet-quality scores the magnitudes of the effects remain insignificant. Finally, we did not find any difference for the HEI Vegetables between nutritional supplements takers and non-takers.

Finally, propensity-score matching estimators critically hinge on the assumption of unconfoundedness or CIA. Hence, PSM cannot provide consistent treatment estimates if the assignment to treatment is endogenous; such that unobserved variables critically affect the assignment process and related outcome estimates. In order to estimate the extent to which potential unmeasured and/or unobserved factors may bias our treatment effects, we conducted Rosenbaum bounds sensitivity analysis on both HEI and BMI models [ 51 ]. The bounds tests validate the estimated ATTs, while setting the level of hidden bias to a certain value, allowing us to directly asses the required size (or strength) of the unobserved selection variables such that the estimated ATTs would violate the CIA condition. Based on Wilcoxon signed rank tests, the results suggest that the average treatment effects in Tables 3 and 4 and underlying propensity score models in Tables 1 and 2 are robust against the hidden bias of unobserved selection variables. The estimated values of hidden bias needed to render our effects estimates a non-random range around 1.1, i.e. a value confirmed to indicate robustness in the literature [ 52 ]. The test results are available from the author upon request.

Conclusions

Our study shows that the propensity to consume nutritional supplements is a function of diet quality, health, demographic and lifestyle factors. Our findings also suggest a possible link between diet-health behavior (supplement intake) and obesity status as measured by BMI. Thus, consumers of diet supplements do show a lower BMI compared to non-takers. Given decreasing intake levels of fruits and vegetables, it is important to determine the role nutritional supplements play in health behavior and in determining diet quality outcomes.

Indeed, we find that nutritional supplements intake may have a positive effect on diet quality of supplement consumers, which in turn may affect diet health outcome indicators, such as the BMI. However, the effect of supplement intake as an explicit health behavior does not significantly alter the levels of overall diet quality or any of its important sub-components observed in this study. This finding expands the results commonly found in consumer stated preference surveys on diet-health in that a direct linkage between preventative health behaviors and the consumption of fruits and vegetables exists [ 10 ].

However, the estimated differences in obesity and diet quality outcomes between nutritional supplement takers and no-takers should not be interpreted as the causal effect of supplementation. Instead, the binary supplement intake variable in the PSM analysis represents a proxy of individual’s (supplement taker’s) health behaviour, which results in significant differences in the chosen outcomes when compared against a control (non-taker) population.

The results of the analysis suggest that several health indicators, demographics, and lifestyle variables significantly affect the selection into the treatment group of nutritional supplement takers. Nutritional supplement intake is positively associated with a significantly lower BMI of above 1kg/ (body height in meters) 2 , when all other observable characteristics between supplement takers and non-takers are controlled for. We also found that supplement takers are likely to be white, highly educated, of higher household income, non-smokers and of overall higher health status.

The findings reveal that food stamp recipients and lower income households do not take nutritional supplements, even though these two groups may be especially at-risk groups of failing to meet recommended intake levels for major fresh food categories (e.g. fresh fruits and vegetables). On the other hand, individuals of normal weight (individuals with a lower BMI) and individuals who consume more fruits were found to proactively hedge against health risks by consuming nutritional supplements a preventative measure for maintaining good health. One way to encourage consumption of nutritional supplements among at-risk groups would be to establish a health policy on consumption, especially with regards to fruits and vegetables and nutritional supplements, in order to target specific at-risk populations.

Given the increasing importance of individuals’ dietary choices to consumer diet-health and public policy in the United States, accurate estimates of existing behaviors and their impacts on relevant health outcomes have become essential tools for the purpose of policy guidance. Moreover, greater general awareness of diet-health issues and trends toward proactive health behaviors have increased consumers’ demand for more products with identifiable health benefits (e.g. superfoods, functional foods). This trend towards “nutritionism” [ 77 ] demands significant adjustments on the side of stakeholders along many agri-food value chains. Given the recent volatility in the in the U.S. produce sector, growth opportunities related to diet-health trends should be of even greater important to the fresh fruit and vegetable industry. In this context knowledge of the determinants of nutritional supplement demand seems particularly essential.

Finally, a key component in the quest for improving food policies is the improvement in analytical methods aimed at eliminating the self-selection bias and resulting mismeasurement commonly associated with working with cross-sectional observational data, such as NHANES. The econometric analysis carried out in this article contributes to the discussion regarding whether consuming supplements leads to positive diet-health outcomes. Appropriate methods such as treatment effects estimators (e.g. PSM) can provide more reliable insights into an individual’s diet and health behavior, which will provide the prerequisite for effective and efficient public policies.

Supporting information

S1 table. descriptive statistics of variables..

https://doi.org/10.1371/journal.pone.0185258.s001

S2 Table. Standard bias for different matching algorithms.

https://doi.org/10.1371/journal.pone.0185258.s002

S3 Table. Reduction in self-selection bias and covariate balancing.

https://doi.org/10.1371/journal.pone.0185258.s003

S1 Dataset.

https://doi.org/10.1371/journal.pone.0185258.s004

• 1. Agudo A. Measuring Intake of Fruit and Vegetables. Background paper for the Joint FAO/WHO Workshop on Fruit and Vegetables for Health, September 1–3, 2004, Kobe, Japan 40. 2005. Accessed at: http://www.who.int/iris/handle/10665/43144 .
• View Article
• PubMed/NCBI
• Google Scholar
• 5. Center for Nutrition Policy and Promotion (CNPP). Dietary Guidelines for Americans 2010. 2010. http://www.cnpp.usda.gov/sites/default/files/dietary_guidelines_for_americans/PolicyDoc.pdf
• 7. U.S. Department of Agriculture / U.S. Department of Health and Human Services (USDA/HHS). Dietary Guidelines for Americans 2010. Washington, DC U.S. Government Printing Office. 2010. www.cnpp.usda.gov/sites/default/files/dietary_guidelines_for_americans/PolicyDoc.pdf .
• 9. Dickinson A, Shao A. Multivitamins and Other Dietary Supplements for Better Health. 2006;Position paper prepared for the Council for Responsible Nutrition.
• 10. Mintel. Vitamins, Minerals and Supplements US—September 2015. Mintel Academic Reports. 2015. www.mintel.com .
• 11. DeVol R, Bedroussian A. An Unhealthy America: The Economic Burden of Chronic Disease. Milken Institute. 2007. www.milkeninstitute.org/publications/view/321
• 17. U.S. Department of Agriculture/U.S. Department of Health and Human Services (USDA/HHS). Dietary Guidelines for Americans 2015. Washington, DC U.S. Government Printing Office. 2015. http://health.gov/dietaryguidelines/ .
• 18. Institute of Medicine. Dietary Supplements : A Framework for Evaluating Safety . 2005;Washington, DC: National Academies Press.
• 34. Grossman M. The Human Capital Model and the Demand for Health. In: Culyer A.J. and Newhouse J.P. eds. Handbook of Health Economics . 1999;North Holland: Elsevier. pp. 347–405.
• 38. Grilli L, Rampichini C. Propensity Scores for the Estimation of Average Treatment Effects in Observational Studies. 2011;Training Sessions on Causal Inference, Bristol.
• 48. Centers for Disease Control and Prevention (CDC). National Health and Nutrition Examination Survey 2003–2004. 2010. http://wwwn.cdc.gov/Nchs/Nhanes/Search/nhanes07_08.aspx .
• 51. Rosenbaum PR. Observational Studies, 2 nd ed. 2002;New York, Springer.
• 52. DiPrete TA, Gangl M. Assessing bias in the estimation of causal effects: Rosenbaum bounds on matching estimators and instrumental variables estimation with imperfect instruments.” No SP I 2004–101, Discussion Papers, Labor Market Policy and Employment from Social Science Research Center Berlin (WZB). 2004; http://econpapers.repec.org/paper/zbwwzblpe/spi2004101.htm .
• 54. Kahle L, Buckman D. Calculation of Mean Healthy Eating Index-2010 Component and Total scores and Corresponding Standard Errors and Confidence Intervals for a Population, Subpopulation, or Group. Information Management Services Inc. 2013. www.cnpp.usda.gov/sites/default/files/healthy_eating_index/Readme_HEI2010_NHANES0708_PopulationScore.pdf
• 66. United States Department of Agriculture- Food and Nutrition Service (USDA-FNS). Determining Product Eligibility for Purchase with SNAP Benefits. 2010. www.fns.usda.gov/sites/default/files/eligibility.pdf .
• 77. Scrinis G. Nutritionism: The Science and Politics of Dietary Advice: The Science and Politics of Dietary Advice. New York and Chichester: Columbia University Press 2013; pg:352.

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• Europe PMC Author Manuscripts

The balance between food and dietary supplements in the general population

Dr. marleen ah lentjes.

University of Cambridge, Department of Public Health & Primary Care, Strangeways Research Laboratories, Worts Causeway, Cambridge CB1 8RN

Associated Data

In the past, vitamins and minerals were used to cure deficiency diseases. Supplements nowadays are used with the aim of reducing the risk of chronic diseases of which the origins are complex. Dietary supplement use has increased in the UK over recent decades, contributing to the nutrient intake in the population, but not necessarily the proportion of the population that is sub optimally nourished; therefore, not reducing the proportion below the estimated average requirement and potentially increasing the number at risk of an intake above the safety limits. The supplement nutrient intake may be objectively monitored using circulation biomarkers. The influence of the researcher in how the supplements are grouped and how the nutrient intakes are quantified may however result in different conclusions regarding their nutrient contribution, the associations with biomarkers in general, and dose-response associations specifically. The diet might be sufficient in micronutrients, but lacking in a balanced food intake. Since public health nutrition guidelines are expressed in terms of foods, there is potentially a discrepancy between the nutrient-orientated supplement and the quality of the dietary pattern. To promote health, current public health messages only advocate supplements in specific circumstances, but not in optimally nourished populations.

Introduction

The micronutrients that we have come to know as ‘vitamins’, had their road of discovery pathed by a multitude of deficiency diseases. A clear intervention, then still in the form of foods, relieved symptoms and cured diseases such as limes & scurvy, unpolished rice & beri beri and cod liver oil & rickets. Diseases nowadays are not marked by deficiency, rather overconsumption of foods tends to be the major cause of chronic diseases such as cardiovascular disease, diabetes and cancer ( 1 – 3 ). These lifestyle diseases are multifactorial, where diet/nutrients play a role in disease development; however, more than a narrow focus on micronutrients is necessary to treat or prevent them.

Yet, dietary supplements remain popular in the general population where supplement users have been labelled as the ‘worried well’. Positive beliefs about supplements, such as “Help me to be healthy”, “Stop me getting ill”, “Not do me any harm” and “Be the best I can do for myself” have been observed among supplement users in the UK ( 4 ). A Dutch survey found that 61% thought that supplements were ‘sufficiently proven’ and 48% believed that supplements were ‘an easy way to stay healthy’ ( 5 ). Also in NHANES (US), reasons for supplement use relate to disease prevention/treatment and supplementing the diet ( 6 ). These opinions are in contrast with public health guidelines in these countries, where there is -in general- no role for supplement use for adults, apart from illness/special conditions, and more recently, for vitamin D supplementation in at risk groups in the UK ( 7 , 8 ).

So, is there a role for dietary supplements? Should we have to make up a balance of food vs. supplements even if health guidelines are not encouraging the use of dietary supplements? The fact that supplements continue to be used, means that the general population derives nutrients from both foods and supplements and the supplement contribution may be substantial. Supplement use is therefore an exposure that cannot be ignored in relation to (i) nutrient deficiency, sufficiency and toxicity, (ii) biomarker associations and sometimes (iii) disease, in case of suboptimal nutrient status or food intake ( e.g. fish vs. fish oil and the association with cardiovascular disease). Alternatively, in observational research it is not always about establishing whether there is a benefit from supplement use itself, but also, how can we control for this health-seeking behaviour when we are interested in this (or another) exposure and health ( 9 ). ‘The typical supplement user' does not exist, there is heterogeneity in the characteristics of supplement users, depending on the type of supplement consumed ( 10 – 13 ). Therefore, adjusting the supplement-disease analyses for 'yes/no supplement use' might not take away the suspected confounding, but could potentially create (more) noise/attenuation in the associations.

This paper aims to describe dietary supplement assessment methodology in the context of observational research and characterise the heterogeneity amongst supplement users. A secondary aim is to focus on the role of supplements in the nutrient distribution, circulating biomarkers and disease, using a variety of examples illustrating their (in)effectiveness in public health.

Dietary supplement assessment: definition, instruments and prevalence of use

Within Europe since 2002, dietary supplements have been regulated by the directive 2002/46/EC which defines supplements as ( 14 ): “ Food stuffs the purpose of which is to supplement the normal diet and which are concentrated sources of nutrients or other substances with a nutritional or physiological effect, alone or in combination, marketed in dose form, namely forms such as capsules, pastilles, tablets, pills and other similar forms, sachets of powder, ampoules of liquids, drop dispensing bottles, and other similar forms of liquids and powders designed to be taken in measured small unit quantities .” Definitions of what are considered to be ‘dietary supplements’, or indeed specific types of supplements, have been reported to vary across American surveys ( 15 ). Also in UK studies, definitions are lacking although the answer categories or the examples given to participants in the questionnaires give an indication of what was studied ( 10 , 16 , 17 ). Depending on the aim of the study, prescribed medication (as sources of folate, calcium and iron) can be included in order to calculate what is known as ‘total nutrient intake’ (TNI), i.e. the sum of nutrient intake from foods and supplements ( 18 ). Moreover, separating medication-derived nutrients from dietary supplements (or indeed food intake from dietary supplement intake) might provide additional information regarding reverse causality or confounding by indication, which might obscure the association with biomarkers or illness, e.g. the use of prescribed ferrous sulphate for anaemia, which itself might be caused by an underlying illness/treatment, will be differently associated with health than ferrous sulphate part of a multivitamin/multimineral (MVMM) supplement consumed out of choice.

The following issues arise when wanting to assess the nutrient contribution from supplements: (i) the potential for short-term use by participants, (ii) constant change in the supplement supply and (iii) constant change in supplement composition. The choice of the dietary supplement assessment instrument will have consequences for how well these issues can be dealt with. Dietary supplement use is assessed in similar ways to diet. There is self-reported data, using a variety of questionnaires, as well as objective measures, in the form of biochemical markers each with advantages and disadvantages ( Table 1 ). The gold standard in supplement assessment is considered to be a face-to-face supplement inventory, which enables label transcription and/or collection of supplement bottles to retrieve nutrient composition as well as tablet count and hence provides very detailed information. This method has been applied in sub-cohorts or pilot studies, mainly to validate questionnaires ( 19 , 20 ). Label transcription has also been applied in the UK National Diet and Nutrition Surveys (NDNS) and the North/South Ireland Food Consumption Survey. General questionnaires can include question(s) regarding supplement use. Answer categories will enable categorisation into non-supplement users (NSU) and supplement users (SU) and might ask more detailed (possibly in free text) information on the type of supplement used, such as frequency or dose. The recall time and words such as ‘regular’, ‘usual’ or ‘seasonal’ will reflect the prevalence of supplement use obtained ( 21 , 22 ). In a Supplement Frequency Questionnaire (SFQ) , supplements are grouped, for example ‘fish oils’, ‘vitamin C’, ‘one a day multivitamins’ and frequency and/or amount of use are asked for each supplement group, sometimes specifying a minimal frequency of use required ( 23 ). The nutrient intake is calculated by assuming a nutrient formulation for each of these supplement groups. The recall period varies between studies and can be up to 10 years ( 23 ). A recall covers a period of 24h, whereby supplement nutrient intake can be calculated using default nutrient profiles or manufacturers’ data matched to the exact supplement used, multiplied by the frequency of consumption. The number of days collected will influence the findings regarding prevalence of supplement use ( 24 ). In records , supplements can be recorded as they are consumed, which could minimise omissions due to forgetfulness (and thereby the potential for recall bias) and capture full label content. Participants are asked to fully describe the supplement, the dose (or enclose the label), the quantity and potentially also the clock time. The number of days collected will influence the results regarding prevalence of supplement use. Biomarkers , such as blood or urine samples, tend to be used to measure concentrations of the compound of interest or its metabolite. Biomarkers cannot differentiate between sources of the nutrient ( i.e. whether the vitamin C was derived from foods or supplements), they vary in reference time (they may reflect recent or long-term exposure) and some nutrients are homeostatic or may be affected by illness. Laboratory measures are independent of errors made during self-report, but sample collection can be burdensome for the participant as well as expensive.

Bracketed ticks (✓) indicate that the measure is not uniform in its characteristic/use, see examples in text.

In summary, all these instruments have limitations and the quality of the data obtained will influence how the obtained data may be used in analysis. Supplement-disease analysis may be fraught with confounding when simply comparing SU against NSU; supplement nutrient intake may require researchers to maintain time-consuming, detailed supplement composition data; while biomarkers will leave the researcher with a sample concentration, but without an idea of what was actually consumed. Indeed, a combination of instruments might be a better way forward ( 18 , 25 ). The choice of instrument is reflected in the prevalence of dietary supplement use observed. By using a similar instrument, secular trends can be monitored. Using a one year recall, the NDNS in 2012/13-2013/14 estimated the use of any type of dietary supplement in the UK among adults aged 19-64 years to be 15% in men and 24% in women and for those >=65 years, 30% and 41% respectively ( 26 ). In years 5 and 6 of the rolling programme, the percentage using dietary supplements has not changed greatly for the oldest age category (38% and 41% respectively); for the younger age groups, up to a threefold increase was observed. Compared to earlier adult survey data collections in 1986/87, the change has been substantial since it was estimated to be approx. 9% and 17% respectively ( 27 ). Secular trends have also been observed in the US, where the use of any type of supplement might have stabilised, but, for example, vitamin D supplementation increased between 1999 and 2012 from 5% to 19% and omega-3 containing supplements increased 7-fold up to 13% ( 28 ). A trend analysis of supplement use in the Health Professionals Follow-Up Study and the Nurses’ Health Study indicated continued increase of supplement use up to 2006, but a marked decrease of beta-carotene after 1994, partly because trials suggested potential harm ( 29 ). The changes in trends may be a consequence of health policies ( e.g. Healthy Start) and/or media coverage of trials. Supplement use varies greatly across Europe ( 30 ), both in prevalence and in the type of supplement consumed. Comparisons across countries are hampered by the variety in recall time and choice of instrument. In EPIC-Europe, the choice of a single 24h recall between 1995-2000 might have underestimated the ‘usual’ supplement exposure; however, a clear North-South gradient was observed ( Figure 1 ), as well as positive trends with age ( 31 ). The stark differences in the prevalence of supplement use between countries and continents needs to be considered when comparing results regarding supplement-sourced nutrient intake between studies.

Supplement nutrient intake - extremes of the distribution

All of the above listed assessment instrument -except the biomarkers- require the researcher to make assumptions regarding the supplement nutrient composition. The pre-structured questionnaires will assume a default nutrient composition. Open-ended questionnaires, such as used in the NDNS ( 32 , 33 ) and in the Norfolk arm of the European Prospective Investigation into Cancer (EPIC-Norfolk) study ( 34 ), can be more specific, but will equally rely on the labels printed on dietary supplement packaging, and therefore the potential for label-transcription errors ( 35 ). The packaging may contain errors, the supplement may have been kept in poor storage conditions or the supplement may contain ‘overages’, the latter mainly for vitamins, and taking into account safety limits, in the range of 5-100% of the label value ( 36 , 37 ). All these factors make what is ‘on the label’ not an accurate reflection of what is ‘in the dietary supplement’ and therefore a less accurate -or possibly even biased- measure of supplement nutrient intake (at least attenuating any association between nutrient intake and the biomarker or disease). A long-term process of developing a composition table based on analytical data has for these reasons been proposed and developed ( 38 , 39 ).

Once the nutrient intake from supplements is assessed, it can be added to the food-sourced intake, to obtain TNI. This widens the range of the studied nutrient, and therefore enables risk assessment at either side of the nutrient intake distribution ( Figure 2 ). The ‘at risk’ population is situated in the tails of the nutrient intake distribution (either because the intake remains low or becomes too high after inclusion of supplement sources), the intakes of which are less accurately measured. For this reason, researchers may take the upper/lower 5 th centile of the nutrient intake distribution as a more stable assessment rather than the proportion in the distribution above or below the exact cutoff set by the Dietary Reference Values (DRV) ( 40 , 41 ). When a limited number of dietary intake days are collected, researchers prefer application of statistical techniques such as ‘Shrink & add’ or ‘Add & shrink’ (see the measurement error webinar series for information about these methods ( 42 )). The TNI distributions are used to establish the contribution that supplements make in meeting or exceeding DRVs. The Estimated Average Requirement (EAR) is used for comparing populations against a standard. It is the average nutrient requirement in a healthy group of people meant to maintain sufficient concentrations of a particular biomarker (blood/tissue concentration; enzyme saturation) in order to prevent nutrient deficiencies. The exact requirement is often unknown and assumed to be symmetrical ( 40 ), but reasonable estimates of the proportion at risk can be obtained using the EAR cut-point method ( 43 ), which assumes that the proportion below the average nutrient intake is -under certain conditions- approximately the same as the proportion of people with an intake below their average nutrient requirement. The Lower Reference Nutrient Intake (LRNI) is the EAR value minus two standard deviations and is likely to cover the need of only 2% of the population. The Reference Nutrient Intake (RNI) is the EAR value plus two standard deviations, and covers the need of 98% of individuals in a population ( 40 , 43 ). The RNI might provide a good estimate for comparison against an individual’s requirement; however, at the population level, this measure is (too) cautious ( 43 ). The Safe Upper Level (SUL) is defined by the Expert Group on Vitamins and Minerals (EVM) to “represent an intake that can be consumed daily over a lifetime without significant risk to health on the basis of available evidence” ( 36 ) and refers to the supplement-sourced intake only. The Guidance Level (GL) is defined by the EVM as “an approximate indication of levels that would not be expected to cause adverse effect, but have been derived from limited data and are less secure than SULs” ( 36 ).

DRV, dietary reference value; LRNI, lower reference nutrient intake; EAR, estimated average requirement; RNI, reference nutrient intake; SUL, safe upper level

Considering the variation in supplement use across Europe ( 30 , 31 ), supplements vary in the contribution that they make to food-sourced intake and the proportion of the populations at risk of not meeting the sufficiency DRVs. There are however various complications when wanting to assess this across countries, not in the least because of different dietary assessment methodologies applied in surveys, but also what is considered ‘sufficient’ across countries varies due to ( 44 , 45 ): different expert panels, the currency of the evidence assessed, use of different DRVs, different cut-off points for age groups, criteria for adequacy ( i.e. the condition that the nutrient needs to prevent) and the extrapolation of data. Mensink et al. ( 46 ) streamlined participant-level data with regard to DRVs and age cutoffs from dietary surveys in eight countries in the European Union, with data collections between 1997 and 2010. Using vitamin C from this publication as an example, mean food-sourced intake in adults aged 18-60 years varied from 81 (PO) - 152 (G) mg/d in women and from 81 (F, NL) -152 (D) mg/d in men. After the contribution of supplements, TNI ranged from 96 (F) -175 (D) mg/d in women and from 87 (F) -173 (D) mg/d in men. There was a very small decrease (0-1% women; 0-0.7% men) in the percentage of the populations meeting the EAR after inclusion of supplements; only among the 65+ age group were reductions of 0-4% obtained. Particularly for the vitamins A, D and E, and the minerals iron (among women) and selenium, a lower prevalence of intakes below the EAR (up to 34% decrease for vitamin D) were observed after inclusion of supplement sources of these nutrients in adults. When it comes to exceeding upper limits due to supplements, Flynn et al. ( 30 ) studied dietary survey data of seven vitamin and eight mineral nutrient distributions gathered in a selection of European countries between 1994 and 2006. Food-sourced intake (with fortified foods making a small contribution) was responsible for the majority of the populations’ intakes. The nutrient intake associated with the 95 th centile of retinol, zinc, iodine, copper and magnesium increased considerably after inclusion of supplement sources; however, it only exceeded the upper limits in a small percentage of the studied populations.

When supplement use is compared between countries or continents, its use and contribution do not only vary because of participant-associated variation ( i.e. the choice of supplement), but also due to the choices in data handling and analysis by researchers. When comparing publications, large differences between studies may be explained due to SUs all being grouped together vs. nutrient-by-nutrient distinction among SUs. This is the case when interpreting publications using NHANES data for example ( 47 – 49 ). Here, far greater effects on meeting the EAR and exceeding the TUL are obtained because of different supplement nutrient groupings of participants (on top of different DRV cut-offs and the majority of the supplements being MVMM-type supplements). Applying this nutrient-by-nutrient grouping strategy and UK DRVs to the vitamin C intake as assessed in the NDNS data of years 1-4 of the rolling programme ( 32 ), then SUPP-Table 2 is obtained. When the food-sourced vitamin C intake of all the men or all the women within the same age group are compared against the TNI, the median intake increased with 3-9 mg/d and the percentage of participants in this population not meeting the EAR was maximally 0.1-1.1% lower once supplements were included, as was observed EU-wide ( 46 ). When we additionally ask the question “Who is at risk?” and stratify the strata further by supplement status, we can allocate the supplement exposure to those who were truly exposed and not dilute the exposure with non-vitamin C containing supplements. When the vitamin C supplement users (SU+C) are identified, the contribution of the supplement was approximately twofold that of the food-sourced intake ( SUPP-Table 2 ). The SU+C group had a lower risk of not meeting the sufficiency DRVs (not just because of the supplement, but also because of higher food-sourced vitamin C intake among the SU-C and SU+C); moreover, only the SU+C group, and only when studying TNI, were exceeding quantities >1000 mg/d, intakes which have been associated with GI-problems ( 36 ). A visual representation of this TNI distribution and DRVs is provided in Figure 3 .

TNI, total nutrient intake (food + supplements); NSU, non-supplement users; SU, supplement users; SU+C, supplement user consumes a vitamin C containing supplement; SU-C, supplement user consumes a supplement without vitamin C; NDNS; national diet and nutrition survey; LRNI, lower reference nutrient intake (10 mg/d); EAR, estimated average requirement (25 mg/d); RNI, reference nutrient intake (40 mg/d); 1000 mg/d being the intake at which GI-problems have been reported.

Conclusion - intake

Supplement intakes shift the nutrient exposure distribution to the right; however, nutrient sufficiency -in most cases- may be obtained from food sources only. The (small) reduction in the proportion at risk after including supplements depends on the nutrient, but also on the grouping of the supplements. There is a modest higher risk of exceeding the upper limits when supplement intake is included (among those using that nutrient in supplement form).

Association between supplement intake and biomarkers

Objectively measured nutrient biomarkers may serve to validate the self-reported nutrient intake, by providing an indication of the ‘internal dose’, the absorption. Biomarkers may be influenced by a variety of factors described in detail elsewhere ( 50 , 51 ); however, with regard to dietary supplements as a source of nutrient intake, a few points stand out. First, the range of nutrient intake is made wider and different dose-response associations may be detected with TNI vs. food-sourced intake alone. Secondly, the statistical parameters chosen in observational research are mostly there to establish correlations and quantify reclassification of participants, but a dose-response association is different and some of these results may be counterintuitive with regards to the ‘internal dose’. Thirdly, just as foods contain multiple nutrients which may interact ( e.g. fat-soluble vitamins as antioxidants in high fat foods), colinearity in supplement nutrient ingestion exists ( e.g. use of MVMM-type supplements). Therefore, biomarkers other than the nutrients studied may be affected ( e.g. vitamin C supplement use and tocopherol concentrations). These points are illustrated below.

In (large) cohort studies, circulating biomarkers are commonly used as an indicator of absorption/bio-availability. The nutrient exposure may be classified into N -tiles (e.g. tertiles, quintiles) and the means of both intakes and biomarkers may be presented for each N -tile, this to establish any type of dose-response association. Researchers may be interested in the (improvement of the) agreement in classification between the objectively and subjectively collected data, i.e. establish whether participants ranked and placed into a specific N -tile according to the biomarker are the same participants as those placed in this N -tile according to the questionnaire (comparing this agreement using the intake without and with supplements). Alternatively, researchers may wish to summarise the association between intake and biomarker in a single number, using either (i) a correlation or (ii) a beta-coefficient. A correlation is a standardised measure (disregarding the unit) indicating the strength between two variables. If the correlation is high, then a standardised higher intake is associated with a standardised higher or lower biomarker concentration; however, it does not reflect a dose-response association (even when the value approaches 1 or -1), since the standardisation process has removed this aspect from the results. Using linear regression, which obtains the (adjusted) beta-coefficient, the unit in which the variables are measured remains (though the input variables might be ‘transformed’), and the results may be interpreted as a ‘dose-response’ since the intake of x amount of mg/d can be associated with a higher/lower y amount of the biomarker. For example, correlations between TNI or supplement-sourced vitamin E intake and α-tocopherol concentration biomarkers have been reported to range from 0.3-0.7 using a variety of parameters on transformed or non-transformed data ( 52 – 55 ). In the VITamin And Lifestyle (VITAL) cohort ( 52 ), adjusted correlations between supplement intake and biomarker were 0.69 with a significant linear trend across N -tiles ( P <0.0001); however, when plotting the means of the supplement intake groups (NSU: 0; quartiles: 18, 180, 194, 360 mg/d) against the blood biomarker (NSU: 28, quartiles: 34, 44, 50, 60 µmol/L), three issues become apparent. (i) Supplement-sourced intake exceeds food-sourced intake 30-40 fold; (ii) due to the non-normal distribution of supplement-sourced intake, a wide range of supplement-sourced intake is grouped together, creating then small, then large differences between the N -tile means of intake; and consequently (iii) the dose-response of supplement intake is not the same at every amount of supplement-sourced vitamin E intake. Such observations were also observed by Zhao et al. in the Irish National Adult Nutrition Survey (NANS) data ( 56 ). α-Tocopherol concentrations are positively associated with vitamin E intake, γ-tocopherol is negatively associated with vitamin E intake due to preference of hepatic α-tocopherol transfer proteinase; furthermore, potential differences in the associations of plasma tocopherol and natural vs. synthetic forms of vitamin E may exist ( 57 ).

When assessing the association between nutrient intake (from both food and supplement sources) and a biomarker, Block et al. draw an analogy with smoking ( 58 ). When the association between smoking and a nicotine biomarker is assessed, we could analyse the amount smoked at home separately from the amount smoked at work, or analyse the amount smoked at work adjusted for the amount smoked at home, however the total amount smoked is the exposure of interest in aetiology ( 58 ). Moreover, when applied to nutrient-biomarker associations, the biomarker has no ability to detect a difference between food or supplement sources. One more analogy may be added to the ones listed by Block et al. and that is that we would not average the number of cigarettes smoked whilst including the non-smokers. However, this is what happens by grouping all SUs into a single group, the supplement contribution of a nutrient is diluted by SUs who consume different types of supplements. A nutrient-by-nutrient supplement group distinction can provide insights not only in potentially differential food-sourced intakes (as described above in the intake distribution section), but also in potentially differential dose-response associations. Particularly so, since supplement-sourced intake could surpass food-sourced intake and therefore approach intakes associated with biomarker saturation. In the EPIC-Norfolk study, dose-response associations have been observed to vary across subgroups of SUs. A sex-adjusted analysis of published results ( 59 ), obtains the following associations between food-sourced vitamin E intake (per 10 mg/d) and back-transformed log-biomarkers of α-tocopherol concentrations (and therefore representing a percentage change [95%CI]) among NSU, SU-E and SU+E respectively of: 10% (9,12%), 9% (6,12%) and 5% (2, 9%). When replacing food-sourced intake with TNI, the associations in the SU+E group weakened to 1% (1,2%); although the adjusted correlation strengthened from 0.09 (food only) to 0.43 (TNI) among the SU+E (since supplement-sourced vitamin E intake may be over 10-fold higher than food-sourced intake in the UK). This linear model indicates saturation, which has been reported with intakes varying between 9-17 mg/d ( 54 , 60 ); and indeed, when only participants with TNI <17 mg/d were included, the coefficient among the SU+E was 9%, although with wide confidence intervals (1-16%). The urinary excretion products of vitamin E have for this reason been studied as a substitute to indicate sufficiency, or very high ingested doses ( 54 ). Saturation thresholds also exist for vitamin C since kidneys excrete vitamin C at intakes higher than 120 mg/d ( 40 ); whereas retinol concentrations are largely homeostatic, even after a state of toxicity has been reached ( 61 ) and therefore dose-response associations are not observed in replete individuals.

The omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are mostly obtained from oily fish, for which the most recent dietary guideline recommendations (1 portion of oily fish per week, approx. 0.45 g/day or 3.15 g/week of EPA+DHA) ( 62 ) have not been met in the UK population ( 32 , 33 ). A source of EPA and DHA may also be obtained from cod liver oil and fish oil type supplements (referred to as ‘EPA/DHA-containing supplements’), which could approximately double the exposure among those using EPA/DHA-containing supplements (SU+EPA/DHA). In EPIC-Norfolk, a general population-based cohort, aged between 39 and 79 years, the median TNI was 0.39 g/d in men and 0.29 g/d in women among SU+EPA/DHA between 1993-1998 ( 59 ). For EPA or DHA supplements, when these nutrients are ingested separately or combined, in doses up to 7 g/d ( i.e. over 15 times the SACN recommendation), dose-response associations in trials have resulted in increased plasma concentrations with the most efficient dose-response when the respective fatty acids is supplemented ( 63 ). Dose-response associations between the sum of EPA and DHA intake (3:2 ratio) and plasma EPA and DHA, have been found to be linear up to 3 g/d in a trial of healthy young men who consumed fish <1 times/week at baseline ( 64 ). A trial among healthy men and women aged 20-80 years, who did not consume fish or supplements thereof, showed linear dose-response associations up to 4 portions of oily fish per week (where six capsules totalling 3.27 g of EPA+DHA reflected a single portion) ( 65 ). However in a cohort study where SU+EPA/DHA were excluded and fish consumption was 0.5-1 serving per week, a linear association was observed up to 0.5 g/d of EPA+DHA intake ( 66 , 67 ). The differences in dose-response between cohorts and trials may be explained by differences in bio-availability of food-sourced and supplement-sourced EPA+DHA due to varying fat content of meals and biochemical form of the supplemented fatty acids ( 68 , 69 ) or the frequency of EPA+DHA consumption. Supplements in trials are advised to be taken daily, whereas fish is an episodically consumed food. Browning et al. observed that similar weekly doses of EPA and DHA (6.54 g/wk, i.e. 2 times the SACN recommendation), but taken either daily or dispersed over only 2 days per week, resulted in faster and sustained incorporation into plasma, platelets and red blood cells when supplements were taken daily, although after 12 months no difference was observed in plasma concentration when comparing the weekly vs. the daily regime ( 70 ).

Not just pharmaceutical supplement doses, but also supplement doses not exceeding the RNI are associated with circulating biomarker concentrations. A recent publication from the Lung Cohort Cancer Consortium (LC3) combined cohorts across four continents and analysed biomarkers in a single laboratory ( 71 ). It illustrated a wide range in vitamin status across the continents, with higher concentration among MVMM-type SUs. In the 1994/95 NDNS 65+ sample, vitamin but not mineral intake from supplements, was associated with higher status indices, regardless of the supplement assessment tool used ( 18 ). In the UK, vitamin D is mostly contained in cod liver/fish oil supplements as well as multivitamin and MVMM supplements. Here, the doses do not tend to exceed 5 mcg/d and still 10 nmol/L higher 25(OH)D concentrations were observed among participants in the 1958 Birth Cohort who took such supplements ( 72 ), lowering their risk of a 25(OH)D concentration being <40 nmol/L by 64% (95%CI: 56-70%).

Conclusion - biomarker

The supplemented nutrients are capable of raising plasma concentrations of the respective nutrients, particularly vitamins and fatty acids. Supplements at pharmaceutical doses might obtain high correlations between intakes and biomarker; however, the dose-response associations indicate saturation. A biomarker may be influenced by many other factors (see for example Proc Nut Soc McMillan); moreover, it does not automatically mean that higher circulating concentrations indicate better health or functionality, since circulating biomarkers might not reflect storage or the effectiveness of the nutrient in an organ.

Health outcomes

In this last section, the balance between food and supplements is discussed in light of positive and negative health outcomes. Evidence for causality of a putative beneficial nutrient is generally taken from (double-blinded, placebo-controlled) trials; however, evidence with regards to side effects, contamination or toxicity are mostly gathered from extensive risk assessment using animal models, observational studies and case reports or sensitivity analysis from trial data. I will first contrast these study designs, followed by a summary of systematic reviews evaluating the role of dietary supplements and emphasizing the differences between foods vs . supplements.

Trials and observational studies have advantages and disadvantages when studying associations between supplement use and health/disease ( Table 3 ). Trials are limited in the number of exposures that can be tested in a single experiment ( 23 , 73 , 74 ). The conclusion of dietary supplement efficacy in relation to the outcome is hence limited to the number of compounds tested, the dose tested (potentially higher than a commonly available dose) and the outcome tested. Moreover, particularly when the outcome is cancer, the follow-up in trials tends to be too short since the disease might take 10-20 years to develop ( 75 – 77 ). Trial findings can be obscured by the use of supplements beside the trial dose, particularly when these are unrecorded. Similarly, past use of supplements by trial participants (treatment or control) could obscure findings as well as pre-cancerous stages which may modify the risk to the intervention arm ( 13 , 77 , 78 ). Regarding observational studies and supplements, such studies can be more inclusive in their eligibility criteria and the follow-up time tends to be longer than in trials. They can assess a wide range of commonly used dietary supplements and doses ( 23 ). Depending on the frequency of assessment, cohorts can take into account the variability of supplement use over time, since a single measure cannot be considered to reflect habitual supplement use ( 79 , 80 ). On the other hand, observational studies suffer from confounding and, if retrospective measures are used, potentially recall bias ( 75 , 81 ). The distribution of socio-demographic characteristics, behavioural factors, and prevalent illnesses are not uniformly distributed between SU and NSU ( 23 , 73 , 82 ). Additionally, the role of specific nutrients is difficult to assess due to colinearity, i.e. nutrients are commonly consumed as part of a MVMM-type supplement for which factorial trial designs are better equipped ( 23 , 73 , 77 ).

Since supplements contain (isolated) nutrients in concentrated forms, TNI may lead to chronic intakes exceeding safe upper levels ( 83 ) ( Figure 2 ). In the Iowa Women’s Health Study, supplement use has -potentially for this reason, but also due to confounding by indication- observed harmful associations between supplemental iron and mortality ( 84 ). High retinol TNI (~2500 µg/d) in combination with low vitamin D TNI (< 11 µg/d) has been associated with fractures in postmenopausal women ( 85 ). For Vitamin C the difference between the RNI and (reversible) harm in the form of GI problems ranges between 40 mg/d and 1000 mg/d; whereas for retinol this is 600 µg/d vs. 1500 µg/d (the difference being just over a common vitamin A dose in a supplement). The European Food Safety Authority ( 86 ) and the Expert group on Vitamins and Minerals in the UK have extensively reviewed trials and safety reports for a wide range of nutrients ( 36 ). A selection of the SULs set by the EVM are provided in Table 4 . When compared against the 95 th centile of supplement-sourced intake among the adult population in the NDNS, it is observed that the intake of Zinc and vitamin B6 could exceed the SUL. Although such intakes would need to be sustained over a long period of time to affect health and the collection of a single 4-day diary might not be sufficient to reflect a person’s usual intake or capture the varying behaviour of supplement use.

EVM, expert group on vitamins and minerals; NDNS, national diet and nutrition survey: IQR, interquartile range; BW, body weight; NSU, non-supplement users; SU, supplement users; SU+, supplement user consuming the nutrient of interest in supplement form; SU-, supplement user not consuming the nutrient of interest in supplement form.

Systematic reviews with meta-analyses of trials randomising participants to placebo or single/combinations of anti-oxidant supplements (Vitamin A, C, E, β-carotene, selenium), observed significant associations with harm in unbiased trials (RR 1.04; 95%CI: 1.01, 1.07), but significant beneficial associations (RR 0.91; 95%CI: 0.85, 0.98) for biased trials ( 87 ). Significantly higher all-cause mortality risks were observed for β-carotene (RR 1.05; 95%CI: 1.01, 1.09), and potentially for vitamins A and E, but not for vitamin C or selenium. Also the U.S. Preventive services Task Force recommendation statement concluded that overall no benefit could be observed for primary prevention of cancer or cardiovascular disease when using single nutrient supplements ( 88 , 89 ). A meta-analysis of MVMM-type supplement trials concluded no benefit with regards to total, cardiovascular or cancer mortality ( 90 ).

The Linxian Nutrition Intervention Trials in the general population, studied the effects of the use of any of the four supplement combinations: retinol & zinc, riboflavin & niacin, vitamin C & molybdenum, or ß-carotene, vitamin E & selenium in the prevention of all-cause mortality, cancer mortality and cancer incidence ( 91 ). It observed significant reductions in mortality (9%), cancer mortality (13%), but particularly for stomach cancer (21%) when ß-carotene, vitamin E & selenium were supplemented. Potential explanations for the observed effects were marginal micronutrient intake at baseline due to low consumption of fruits and vegetables. Indeed, plasma vitamin C concentrations were low at the start of the trial and a daily supplement doses of 120 mg/d raised these concentrations comparable to or just below the UK mean. Suboptimal circulating vitamin concentrations have also been proposed as an explanation for the decrease in cancer incidence in the supplementation vs. placebo arm in men of the SUpplementation en VItamines et Mineraux AntioXydants (SU.VI.MAX) trial, since the baseline antioxidant concentrations were lower in men. In post-hoc analysis, an interaction ( P =0.04) between baseline concentrations and trial arm could only be observed for vitamin C and only among men ( 92 ).

Since nutrients may be derived from a variety of (potentially fortified) foods, and not necessarily from foods which are recommended for public health, one can argue that food intake might be a better marker of optimal intake rather than nutrient intake. For example, median vitamin C TNI expressed as a percentage of the RNI was 185% and 197% in men aged 19-64 y and 65+ y respectively, and 192% and 209% in women ( 32 ). Contrasting this to fruit and vegetable consumption, the UK diet meets 30% and 40% of the 5-a-day guidelines in both men and women aged 19-64 y and 65+ y respectively ( 32 ). The role of multivitamins in the past was partly seen as a means to compensate poor dietary choices ( 73 ); or, where after various considerations, the likely benefits outweighed harm of supplement use ( 93 ). However, as observed in above described meta-analyses, such use has not been successful in the prevention of disease or early death in populations. Potentially, since foods contain more than vitamins and minerals alone and dietary patterns as a whole play an important role in health ( 3 ).

An example of a sub optimally consumed food group in the UK is fish, of which the recommendation is to consume 2 portions/week (~280 g/week). In men, intake reached 161 g/week and 252 g/week for the age groups 19-64 y and 65+ y respectively, in women 154 g/week and 189 g/week ( 32 ). Data on the contribution of EPA+DHA from the most commonly consumed supplement, cod liver oils & fish oils, are lacking in the national surveys. These results are available from the baseline EPIC-Norfolk cohort ( SUPP-Table 5 ). The low dose EPA+DHA from mainly cod liver oil resulted in 15-20% more participants meeting the EAR of 0.45 g/d.

Higher fish consumption has been associated with lower CHD/CVD mortality in cohort studies, despite differences across the globe due to differences in dietary assessment methods, absolute amounts of fish consumed, fish preparation and water contamination ( 94 , 95 ). Various biological mechanisms relating to long chain omega-3 fatty acids and CHD have recently been reviewed in these Proceedings, including the prevention of arrhythmia and anti-inflammatory properties ( 96 , 97 ). Fish may also exert its benefit as a source of protein, vitamin D, iodine, calcium (bones), or due to the substitution effect when consumed as part of a meal ( 98 , 99 ). Although, trials using EPA+DHA supplements in secondary/tertiary prevention groups showed promising results initially, later trials observed no benefit ( 100 ). A recent review by the Omega-3 Treatment Trialists’ Collaboration confirmed no benefit in relation to fatal CHD or nonfatal myocardial infarction among those with existing CHD ( 101 ). Supplementation with omega-3 fatty acids for primary prevention of CVD has not been advised due to lack of trial results in primary prevention ( 102 , 103 ) (the results from the first primary prevention trial on Vitamin D and EPA+DHA, the VITamin D and OmegA-3 TriaL [VITAL], are not yet available ( 104 )), only the consumption of oily fish and seafood is currently advocated. Since cod liver oil is a low dose source of EPA+DHA and a commonly consumed supplement in the EPIC-Norfolk study ( SUPP-Table 5 ), it was possible to assess the role of this supplement in primary prevention of CHD mortality. A low dose of 250 mg/d of EPA/DHA is considered sufficient for prevention of arrhythmia ( 105 ). Due to supplement use, an additional 19-24% of the participants met this threshold. The confounding associated with SU+EPA/DHA and SU-EPA/DHA as well as the changes over time in supplement use were modelled using time-varying covariates analysis. It was observed that CHD mortality was 26% lower (95%CI: 16-34%) among SU+EPA/DHA compared to NSU, but no significant association was observed when comparing SU-EPA/DHA vs. NSU ( 106 ). Due to the observational nature of the study, residual confounding and collinearity of nutrients could have occurred.

Conclusion – health

Whenever supplement use and health are being associated, the heterogeneity among SUs cannot be ignored. ‘The typical supplement user’ does not exist. The obvious distinction between SUs lies in the variety of the supplements consumed, but also in the many other disease risk factors which might confound or bias the supplement-health association in observational research. Supplements may be considered ‘natural’; however, the concentrated form puts the user at risk of harm when overdosed. Meta-analyses of trials studying MVMM supplements thus far have indicated that if populations are optimally nourished, there is no role for supplement use - “Enough is enough” ( 107 ).

Closing remarks

How does the balance tip between foods and supplements? Supplements continue to be used by an increasing proportion of the population, so their contribution to diet, health and disease needs to be monitored. Traditionally, essential nutrients have been studied in relation to health, and although micronutrient deficiencies are still prevalent in the UK population, the relatively high nutrient intake may not be a marker of healthy food choices, as reflected in the low fruit, vegetable and fish consumption from national surveys. Resolving unhealthy dietary patterns with micronutrient supplements is a too narrow-minded solution. Nowadays, public health nutrition guidelines take the role of the nutrient, its food source and its place in the diet into account to optimise diet. The current role of supplements herein seems restricted to certain age groups, life circumstances or diseases with impaired nutrient absorption ( 7 , 108 ). The challenge in observational research methodology is to assess and describe nutrient intake, as well as diet as a whole, in the general population and to clarify the role -if any- of nutrient supplements in primary disease prevention.

Supplementary Material

Supplementary table 2 and 5, acknowledgements.

I would like to thank Prof Kay-Tee Khaw and Prof Ailsa Welch for their supervision during my PhD studies. I thank staff at the Elsie Widdowson Laboratories for answering questions on the use of the NDNS datasets and Angela Mulligan for reading over the draft manuscript.

Financial support

The author reports programme grants from Cancer Research UK (G0401527, G1000143) and the Medical Research Council (MRC) (C864/A8257, C864/A14136).

Conflicts of interest

Dietary Supplements: Vitamins Essay (Critical Writing)

Nowadays, there exists a great variety of medications aimed at treating a particular health issue. Due to their number, some of them have quite similar names that can potentially confuse both the patient and pharmacist (Levinthal, 2014).

Sometimes, these drugs can be mistaken due to their common active substance, so they do not do serious harm to the human body. Frequently, however, medication titles can have a direct commercial purpose, as they are created in order to be easily memorized. Such cases can lead to severe health issues and medical errors. According to the statistics published in 2016, the medical mistake was a third leading death cause in the US (Makary & Daniel, 2016). Although misspelled medications constitute a minor part of medical errors, they are still hazardous to people’s health.

In order to define ways to combat the issue, it is important to dwell upon the reasons these errors occur in the first place. According to data, some of the major problems behind medication prescription are legibility and spoken orders (Norman, 2018).

The first matter is highly individual as it concerns doctor’s handwriting that can easily be misread by a pharmacist. The second issue, on the contrary, is an example of medical negligence, as patients are not supposed to know the detailed information on various drugs, and thus, they get confused. As this issue concerns not only medication names but diagnosis and patients’ personal information as well, the healthcare system issue should be completely reconsidered. The best option in terms of records optimization is by creating a working electronic database. By doing so, pharmacists could have electronic access to a patient’s prescription and the probability of medical error would be as minimal as possible.

Levinthal, C. F. (2014). Drugs, behavior, and modern society . London, UK: Pearson Education.

Makary, M. A., & Daniel, M. (2016). Medical error – the third leading cause of death in the US. BMJ, i2139 . Web.

Norman, A. (2018). “Minor” errors in medical records can have major consequences . Web.

• Chicago (A-D)
• Chicago (N-B)

IvyPanda. (2022, February 10). Dietary Supplements: Vitamins. https://ivypanda.com/essays/dietary-supplements-vitamins/

"Dietary Supplements: Vitamins." IvyPanda , 10 Feb. 2022, ivypanda.com/essays/dietary-supplements-vitamins/.

IvyPanda . (2022) 'Dietary Supplements: Vitamins'. 10 February.

IvyPanda . 2022. "Dietary Supplements: Vitamins." February 10, 2022. https://ivypanda.com/essays/dietary-supplements-vitamins/.

1. IvyPanda . "Dietary Supplements: Vitamins." February 10, 2022. https://ivypanda.com/essays/dietary-supplements-vitamins/.

Bibliography

IvyPanda . "Dietary Supplements: Vitamins." February 10, 2022. https://ivypanda.com/essays/dietary-supplements-vitamins/.

• “The Blitzkrieg Myth: How Hitler and the Allies Misread The Strategic Realities of World War II” by John Mosier
• How to Teach Handwriting Effectively
• Pharmacist's Oath, Ethics, and Cultural Competence
• Pharmacist’s Activities and Prescription Process
• The variations in handwriting that lead to individual characteristics
• Effect of Criticism on Development of Appropriate Handwriting Proficiency in Children
• Pharmacist's Role During Opioid Crisis in the USA
• “The Lottery”: Plot, Main Themes, and Opinions
• The Elderly Perception of Pharmacy, Pharmacist and General Health Care
• Handwriting and Writing
• Nutritional Science: Vitamins C, E and D
• Organic Food Is Not a Cure for Environmental and Health Issues
• The Problem of Childhood Obesity
• “Fit and Well” by Thomas Fahey
• Daily Patterns of Anxiety in Anorexia Nervosa

Home — Essay Samples — Life — Dietary Supplements — Short Description Of Dietary Supplements

Short Description of Dietary Supplements

• Categories: Athletes Dietary Supplements

About this sample

Words: 1514 |

Published: May 24, 2022

Words: 1514 | Pages: 3 | 8 min read

Cite this Essay

Let us write you an essay from scratch

• 450+ experts on 30 subjects ready to help
• Custom essay delivered in as few as 3 hours

Get high-quality help

Prof. Kifaru

Verified writer

• Expert in: Life

+ 120 experts online

By clicking “Check Writers’ Offers”, you agree to our terms of service and privacy policy . We’ll occasionally send you promo and account related email

No need to pay just yet!

Related Essays

2 pages / 1061 words

1 pages / 647 words

2 pages / 908 words

2 pages / 725 words

Remember! This is just a sample.

You can get your custom paper by one of our expert writers.

121 writers online

Still can’t find what you need?

Browse our vast selection of original essay samples, each expertly formatted and styled

Related Essays on Dietary Supplements

Maintaining a healthy lifestyle can often be challenging due to the demands of academic responsibilities, extracurricular activities, and social commitments. In recent years, there has been a surge in the popularity of dietary [...]

Spirulina is unicellular and filamentous blue - green algae. Many species in the category of algae and cyanobacteria showed an anti-cancer effect in animal tests, and some of them are in the clinical trials currently. [...]

Pharmaceutical enhancement in sport is a widely discussed topic with arguments both for and against. Pharmaceutical enhancement is a specific form of enhancement in sport and what I will narrow my focus down to due to a [...]

This is a description of a single case evaluation examining a relationship between stress during a test before practicing yoga and after practicing yoga. A single case evaluation is defined as a time series design used to [...]

In volleyball, being a team is important. Your teammates are your friends, well, most of them. We have all dealt with someone who is bossy, constantly tells everyone around what to do as if they took the coach’s place. This [...]

An uproar of conflict has developed concerning the name of an NFL football team, the Washington Redskins. Although the dispute has less publicly been ongoing for years, the problem has been brought into light by a Native [...]

Related Topics

By clicking “Send”, you agree to our Terms of service and Privacy statement . We will occasionally send you account related emails.

Where do you want us to send this sample?

By clicking “Continue”, you agree to our terms of service and privacy policy.

Be careful. This essay is not unique

This essay was donated by a student and is likely to have been used and submitted before

Download this Sample

Free samples may contain mistakes and not unique parts

Sorry, we could not paraphrase this essay. Our professional writers can rewrite it and get you a unique paper.

Please check your inbox.

We can write you a custom essay that will follow your exact instructions and meet the deadlines. Let's fix your grades together!

Get Your Personalized Essay in 3 Hours or Less!

We use cookies to personalyze your web-site experience. By continuing we’ll assume you board with our cookie policy .

• Instructions Followed To The Letter
• Deadlines Met At Every Stage
• Unique And Plagiarism Free

• Environment
• Information Science
• Social Issues
• Argumentative
• Cause and Effect
• Classification
• Compare and Contrast
• Descriptive
• Exemplification
• Informative
• Controversial
• Exploratory
• What Is an Essay
• Length of an Essay
• Generate Ideas
• Types of Essays
• Structuring an Essay
• Outline For Essay
• Essay Introduction
• Thesis Statement
• Body of an Essay
• Writing a Conclusion
• Essay Writing Tips
• Drafting an Essay
• Revision Process
• Fix a Broken Essay
• Format of an Essay
• Essay Examples
• Essay Checklist
• Essay Writing Service
• Pay for Research Paper
• Write My Research Paper
• Write My Essay
• Custom Essay Writing Service
• Admission Essay Writing Service
• Pay for Essay
• Academic Ghostwriting
• Write My Book Report
• Case Study Writing Service
• Dissertation Writing Service
• Coursework Writing Service
• Lab Report Writing Service
• Do My Assignment
• Buy College Papers
• Capstone Project Writing Service
• Buy Research Paper
• Custom Essays for Sale

Can’t find a perfect paper?

• Free Essay Samples
• Dietary Supplements

Essays on Dietary Supplements

Natural supplements, also known as nutritional supplements, are minerals, vitamins, medicinal or botanical ingredients, amino acids, probiotics, antioxidants, and fiber that are eaten to augment a person's diet by supplying extra foods that are not consumed in adequate quantities to enhance optimal health (Valavanidis 69). Aside from the typical substances...

Words: 3640

Found a perfect essay sample but want a unique one?

Request writing help from expert writer in you feed!

Related topic to Dietary Supplements

You might also like.

Should You Be Taking a Fiber Supplement?

Probably not, except for under this circumstance.

“Fiber is a type of carbohydrate that comes from plant foods and cannot be digested or absorbed,” says Kim Yawitz , R.D., a registered dietitian and gym owner based in St. Louis. “It's best-known for promoting regular bowel movements , but it can also help you manage your weight and lower your risk of heart disease , diabetes , and certain types of cancer .”

For men 19–50 years old, the daily recommended intake of fiber is 38 grams, and for men over 50, it's 30 grams. If you're not hitting those numbers, should you be taking fiber supplement ? Keep reading to learn more about fiber, the various types of fiber supplements, and if a fiber supplement may be a good option for you.

What are the health benefits of fiber supplements?

Some guys find it challenging to get the recommended 38 grams daily from diet alone, and this is where supplements might come in handy, Yawitz says. There are a few health benefits of fiber supplements, but there is a caveat, says Maelee Wells Sutton, R.D.N., C.P.T., a personal trainer and dietitian at Endocrine Associates of West Village in New York City. Most of these studies are showing such positive results through dietary changes and supplementation—not supplementation alone. There's very limited research on fiber supplements on their own. So, take these with a grain of salt as you read through.

Promotes Digestion

Promotion of digestive health is the most notable benefit of fiber supplements.

Most fiber supplements consist mainly of soluble fiber, which can ease constipation by softening and bulking up the stool. “Insoluble fiber can also help prevent constipation by speeding up the rate at which food moves through the digestive system,” she says.

Weight Management

Fiber is indigestible, so it has the great power of keeping you fuller, longer. That might help prevent overeating at meals, or snacking in between meals—both of which help limit excessive calorie intake.

Betters Blood Levels

Fiber supplements may also help you keep your cholesterol and blood sugar in check. “For example (and per the FDA ), taking either 3 grams of beta-glucan or 7 grams of psyllium daily can help you lower your total and LDL (‘bad’) cholesterol,” she says. “In a recent clinical trial , adults with type 2 diabetes saw significant improvements in blood sugar after taking 5 grams of beta-glucan daily for 12 weeks.”

Decrease Blood Pressure

It might also help your heart health. A 2023 Nutrition Journal meta-analysis found that taking a 20 gram soluble fiber supplement a day can lower systolic blood pressure by 1.79 mm Hg.

What even is fiber?

Oh, just an MVP of our digestive system, healthy weight management, and so much more.

Lara Clevenger, R.D.N., C.P.T ., a registered dietitian and personal trainer in Port Orange, FL, explains dietary fiber as the portions of plant foods that are resistant to human digestive enzymes. “Fiber is divided into soluble types, like pectin, which ferments in the colon, and insoluble types, like wheat bran, which add bulk and some fermentation occurs in the colon,” Clevenger says.

Dietary fiber has been shown to lower the risk of heart disease, stroke, hypertension, diabetes, obesity, and improve certain gut issues. “Plus, it has been shown to improve cholesterol levels, blood pressure, blood sugar levels in people with diabetes, help with regularity, aid in weight loss, and boost immunity,” she says.

It may be helpful to note that soluble fiber dissolves in water, forming a gel, while insoluble fiber doesn't dissolve in water, shares Yawitz. Your body needs both types. Whole foods with loads of fiber include:

• Leafy greens

What to Know About Fiber Supplementation

Though fiber supplements can help to compensate for fiber deficits, it’s ideal to consume fiber from what’s on your plate (or bowl, or cup).

“It's always best to get fiber from real foods, which offer a much broader range of nutrients than supplements,” says Yawitz. Foods such as black beans are an excellent source of fiber (providing 15 grams per cup), but they're also rich in folate, copper, thiamine, manganese, magnesium, iron, phosphorus, and potassium. Meanwhile, fiber supplements only contain fiber, so as you can gather, you’re missing out on a lot of other potent nutrition specs.

If you're struggling with digestion issues, your doctor or nutritionist might suggest taking a supplement. If that's the case, the type you take depends on what desired outcomes you seek. “If you’re constipated, you may want an insoluble fiber supplement, whereas if you’re a diabetic looking for a little help improving your blood sugar, then you’ll want a soluble fiber supplement,” Yawitz says.

Talk to your healthcare provider about what kind of fiber supplement, if any, might best suit your needs.

Side Effects of Fiber Supplements

A fair word of warning if you do get the green light to go ahead with a fiber supplement: some people find that sudden increases in their fiber intake, especially through supplements, result in negative side effects such as gas, cramping, and bloating, says Wells Sutton. They can also lower the effectiveness of certain medications, like antidepressants and diabetes meds.

If you start one, make sure it’s one that’s third-party tested (look for an NSF or Informed Choice seal on the packaging) and make sure you are drinking a lot of water to allow the fiber to work in your body to the best of its ability. The bottom line is that “while supplements might help, their impact pales in comparison to dietary fiber.”

The side effects of increasing your fiber intake shouldn’t be as severe if you’re doing so through food, but you’ll still want to work your way up gradually. There are a few easy ways to increase your fiber intake through food, Wells Sutton says:

• Drink a smoothie instead of juice, where much of the fiber has been removed.
• Eat a non-starchy vegetable (leafy greens, broccoli, brussel sprouts, etc.) with every meal.
• Snack on fiber-rich foods like nuts, berries, and popcorn.

If your healthcare professional has approved you’re taking a fiber supplement, consult with them to see if they have a favorite brand or any guidelines. Here's a few of our favorites.

Erin Kenney is a Registered Dietitian, personal trainer, and CEO of Nutrition Rewired, a virtual private practice where she helps individuals achieve optimal levels of health and human performance. She takes a holistic approach and helps clients address health concerns from a root cause perspective. She works with athletes, CEO's, fortune 100 companies, and everyday individuals looking to achieve optimal health.

.css-1fpt53b{height:1.25rem;}@media(max-width: 48rem){.css-1fpt53b{overflow:unset;line-height:1.25rem;}}@media(min-width: 48rem){.css-1fpt53b{line-height:1.25rem;}}.css-1fpt53b:before{background-color:#D2232E;color:#fff;margin-right:0.625rem;width:1.25rem;height:1.25rem;content:'';display:block;} Nutrition

Everything You Need to Know About Omega-5s

Can Milk Make You Taller?

Chef Marcus Samuelsson Shares 6 Favorite Things

We’re Cracking The Latest Research On Eggs

Food Scales to Help Hit Your Nutrition Goals

Meal Prep Is Dead. Long Live ‘Snack Prep.’

Great Vegan Meal Delivery Services to Try Today

Beta-Alanine Supplements, Explained

9 Surprising Foods That Will Boost Your Energy

This Is One Supplement You Really Don’t Need

What Vitamins Should Not Be Taken Together?