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Creative Steps to Write a Nutrition Case Study

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Nutrition plays a vital role in improving a patient’s health. However, each patient has unique nutritional needs requiring a personalized healthcare approach. That’s where nutrition case studies come in. These case studies comprehensively assess a patient’s nutritional status and help develop an individualized nutrition plan. They also help to monitor and evaluate the patient’s progress toward their health goals over time. In this article, we will provide a step-by-step guide on  how to write a nutrition case study . This post will help you understand the importance of nutrition case studies, whether you are a healthcare professional or a student.

What Is a Nutrition Case Study?

A nutrition case study comprehensively reports an individual’s nutritional status, dietary habits, and health outcomes . Healthcare professionals typically use these case studies to evaluate and treat patients. This is with various nutritional concerns, such as obesity, malnutrition, or chronic diseases. If you are a nutrition student or practitioner, learning how to write a nutrition case study is an essential skill to have. 

Importance of Nutrition Case Study

Nutrition case studies are a crucial tool for healthcare professionals in nutrition and dietetics. Here are some of the reasons why nutrition case studies are essential:

Provides a Comprehensive Assessment of a Patient’s Nutritional Status

 Nutrition case studies involve a detailed analysis of a patient’s dietary intake, medical history, and lifestyle factors that may impact their nutritional status. This information is used to develop a personalized nutrition plan tailored to the patient’s needs.

Develops an Individualized Nutrition Plan

A nutrition case study’s personalized approach to healthcare leads to an individualized nutrition plan. This approach can lead to better patient outcomes, improved health outcomes, and a higher quality of life for the patient.

Monitors and Evaluates Progress Over Time

Nutrition case studies track a patient’s food intake, weight, body composition, and other health outcomes over time. This enables healthcare professionals to monitor and evaluate the patient’s progress toward their health goals and adjust the nutrition plan as needed.

Provides Education About Healthy Eating Habits and Lifestyle Changes

Nutrition case studies can help educate patients about healthy eating habits and lifestyle changes. By providing a detailed assessment of a patient’s nutritional status, healthcare professionals can help patients make sustainable changes to their diet and lifestyle.

Supports Evidence-Based Practice

Nutrition case studies are based on evidence-based practice, meaning the nutrition plan is grounded in scientific research and clinical expertise. This approach ensures that the patient receives the best care based on the latest research and clinical knowledge.

Steps on How to Write a Nutrition Case Study

Selecting the patient.

The first step in writing a nutrition case study is selecting the patient. Typically, the patient has sought out nutritional counseling or treatment for a specific reason. These reasons include weight management, a chronic disease, or a food allergy. The patient should be willing to participate in the case study and provide detailed information about their diet, health history, and lifestyle habits. When selecting a patient, obtaining their written consent to participate in the case study is essential. This should include an explanation of the purpose of the case study and how their information will be used. It should also add any potential risks or benefits of participating. The patient should know that they can stop participating in the research at any moment if they don’t want to.

Gathering Information

The next step in writing a nutrition case study is gathering information about the patient. This includes a comprehensive assessment of their dietary habits, health status, medical history, and lifestyle factors that may impact their nutrition. To gather this information, you may need to conduct a nutrition assessment, which typically includes the following components:

Anthropometric Measurements

This involves measuring the patient’s height, weight, body mass index (BMI), and other body composition measures.

Dietary Intake Assessment

This involves collecting information about the patient’s dietary habits, including food preferences, allergies, and cultural or religious dietary restrictions.

Biochemical Assessment

This involves analyzing the patient’s blood, urine, or other biological samples to assess their nutritional status.

Medical History

This involves collecting information about the patient’s past and current medical conditions, medications, and surgeries.

Lifestyle Assessment

This involves collecting information about the patient’s physical activity, stress, and other lifestyle factors that may impact their nutrition status. Gathering as much information as possible is essential to create a comprehensive nutrition case study. This information will help you develop an individualized nutrition plan addressing the patient’s needs and concerns.

Developing a Nutrition Plan

Once you have gathered all the necessary information, the next step is to develop a nutrition plan for the patient. The nutrition plan should be based on the patient’s dietary needs, health goals, and lifestyle factors. It should also consider any medical conditions or medications that may impact the patient’s nutritional status. The nutrition plan should include the following components:

Macronutrient and Micronutrient Recommendations

This involves recommending specific amounts of carbohydrates, protein, fat, and other essential nutrients the patient should consume daily.

Food Group Recommendations

This involves recommending specific food groups for the patient, such as fruits, vegetables, whole grains, and lean proteins.

Meal and Snack Recommendations

This involves recommending specific meals and snacks for the patient to meet their nutritional needs throughout the day.

Nutritional Supplements

This involves recommending specific nutritional supplements, such as vitamins, minerals, or protein powders, that may help patients meet their nutritional needs.

Behavioral Recommendations

This involves recommending specific behavioral changes that may impact the patient’s nutrition status, such as increasing physical activity or reducing stress. The nutrition plan should be individualized to the patient’s needs and preferences. It should also be realistic and achievable, considering any barriers the patient may face in following the plan.

Implementing the Nutrition Plan

Once the nutrition plan has been developed, the next step is implementing it with the patient. This may involve educating the patient about healthy eating habits and strategies for making dietary changes. The patient should also be encouraged to track their food intake and monitor their progress toward their health goals. Working collaboratively with the patient throughout the implementation process is essential, as ongoing support and guidance are needed. This may involve regular follow-up appointments or communication via phone or email. The patient should be encouraged to ask questions and share any concerns or challenges they may be experiencing.

Monitoring and Evaluating Progress

The final step in writing a nutrition case study is monitoring and evaluating the patient’s progress. This involves tracking the patient’s food intake, weight, body composition, and other health outcomes. The patient’s progress should be regularly assessed, and adjustments made to the nutrition plan as needed. Objective measures such as laboratory values or body composition assessments are essential to evaluate the patient’s progress. This can help ensure that the nutrition plan is effective and that the patient is progressing toward their health goals.

How to Write a Nutrition Case Study

Once the nutrition plan has been implemented and the patient’s progress has been evaluated, it is time to write the case study. The case study should be organized in a logical and easy-to-read format, and should include the following sections:

Introduction

This should provide an overview of the patient’s case and outline the purpose of the case study.

Patient History

You should provide a comprehensive overview of the patient’s medical history, dietary habits, and lifestyle factors that may impact their nutritional status.

Nutrition Assessment

This should provide a detailed assessment of the patient’s nutritional status, including anthropometric measurements, dietary intake, biochemical markers, and medical history.

Nutrition Plan

This should provide a comprehensive overview of the patient’s individualized nutrition plan. They include macronutrient and micronutrient recommendations, food group recommendations, meal and snack recommendations, nutritional supplement recommendations, and behavioral recommendations.

Implementation and Follow-Up

This should provide an overview of the patient’s progress in implementing the nutrition plan, including any challenges or barriers encountered. It should also outline the follow-up appointments or communication that took place between the patient and healthcare provider.

This should provide an overview of the patient’s progress towards their health goals, including any changes in weight, body composition, or laboratory values.

This should provide an interpretation of the patient’s results, including any limitations or strengths of the case study. It should also provide a summary of the key takeaways and implications for future practice.

Writing a nutrition case study may not be the most exciting task in the world, but it is a crucial one. By following these steps and using a bit of wit and creativity, healthcare professionals can effectively communicate their patient’s nutritional needs . This shows progress toward their health goals. Who knows, maybe writing a nutrition case study will be more fun than you thought!

Abir Ghenaiet

Abir is a data analyst and researcher. Among her interests are artificial intelligence, machine learning, and natural language processing. As a humanitarian and educator, she actively supports women in tech and promotes diversity.

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Medical Nutrition Therapy: A Case Based Approach

• Kathryn M. Kolasa, PhD, RDN, LDN Kathryn M. Kolasa Affiliations Brody School of Medicine at East Carolina University, 3080 Dartmouth Dr, Greenville, NC 27858 Search for articles by this author

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The levels of evidence in nutrition research

Nutrition and health are inextricably linked. Nutrition researchers try to unravel these connections in order to arrive at reliable nutritional advice. However, not all types of research can be used to draw equally firm conclusions. Understanding the different types of study designs is important for distinguishing between reliable and less robust findings. This article explores the various study designs commonly used in nutrition research, their purpose, how strong their evidence is and discusses the strengths and limitations of each design.

Systematic reviews and meta-analysis

A single study is not enough to make a general statement with certainty about a certain link between nutrition and health. That is where systematic reviews and meta-analysis come in: in this type of research, researchers gather all relevant studies on a particular topic and analyse these collectively. As a result, the risk between a certain exposure/factor (e.g., overweight) and outcome/disease (e.g., cancer) can be estimated reasonably well. 1

In a meta-analysis, results of multiple studies are pooled, following a rigorous protocol to find all the original research studies done on a question, and weighted with statistical methods into a single summary estimate. Large and well-conducted studies with high-quality evidence are given more ‘weight’ than small or poorly conducted studies with low quality data. A meta-analysis can only be carried out if the studies look at the same research question and use similar methods to measure relevant variables.

Systematic reviews are similar to meta-analysis, but without the use of a statistical analysis. Although systematic reviews and meta-analysis can reduce bias by pooling data from all relevant studies investigating a particular topic, they are only as good as the studies they include. It is important to check whether data from flawed studies are included or if there are data from studies that use different methods to measure variables – resulting in a comparison of ‘apples and oranges.’ To reduce the risk of bias and improve reporting and transparency, using a set of guidelines called the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) is endorsed by most of the high-quality scientific journals. 2

Randomised controlled trials (RCTs)

A randomised controlled trial (RCT) is a type of intervention study where the researcher actively intervenes to change any aspect of nutrition to see what the effect this has on a certain health outcome.

In an RCT, a group of human subjects with same condition are identified and then randomly allocated to either receive the treatment (e.g., an omega-3 fatty acid supplement) or to a control group that does not receive the treatment (e.g., a ‘placebo’ supplement that looks identical to the original supplement but does not contain the substance being studied). After a defined time period, the effects in both groups are measured and compared to each other. As only one factor is deliberately changed between the groups (and other possible factors that influence the relationship are kept the same or as similar as possible), this type of research can allow us to identify cause-and-effect relationships. 1 These types of study are also used in medical research, for example to  test the effects of new drugs or vaccines.

Preferably, RCTs are performed as a double-blind study: both the researcher and the participants are unaware who is in which group. This is important because a participant’s response or a researcher’s measurement of the outcome could be impacted by knowing who is being treated. For example, the placebo effect is a well-known phenomenon where a person observes an improvement in symptoms or effects in themselves after taking a fake or non-active ‘treatment’ (e.g., pills that don’t contain any active ingredient). On top of that, true randomisation is important. If one group were in some way more ill (or less healthy) than the other group at the start, this might make this group appear to have worse outcomes, even if the administered treatment really had no effect.

RCTs also have limitations. They may not be suitable for answering certain research questions, such the effect of whole diets (e.g., ketogenic, vegan) on the prevention of chronic diseases like cancer or cardiovascular disease. It would be impossible to control compliance (e.g., how strictly the study participants stick to the prescribed diet), a huge number of subjects would be required to show a significant difference in outcome, and it would cost a huge amount of money and time. Furthermore, interventions which deliberately expose participants to something thought to be harmful (e.g., alcohol, smoking, contaminants) or withholding participants from treatment thought to improve health (e.g., certain antibiotics or chemotherapeutic agents) in order to definitely prove a cause-and-effect relationship raise ethical concerns. Time is also an important factor. The more robust and reliable studies are those lasting longer.

It is also important not to generalise results of RCTs too quickly. RCTs often have strict criteria of whom to include and exclude. If a study was only carried out on a specific group of people (e.g., middle-aged women with diabetes), the study may not be applicable to the wider population. Lastly, RCTs may often run for short time periods since they are expensive to carry out. So, they may not be able to tell us about the long-term effects of dietary patterns and changes.

Observational research

Observational research involves simply observing the habits or behaviours in large groups of people to investigate the relationship between lifestyle factors and health outcomes. The researcher does not intervene in any way but compares the health outcomes of people who make different diet or lifestyle choices. These studies are used to identify correlations and develop hypotheses for further testing. 1

For example, researchers observe that people who drink alcohol are more likely to develop lung cancer than those who don’t. However, it may also be that people who drink alcohol also tend to smoke more often and that researchers fail to include this factor into their analysis (e.g., it was not measured or not thought to influence the relationship). Here, smoking is a so-called confounding factor: a factor associated with both the exposure (drinking alcohol) as well as the outcome (lung cancer) and therefore could distort the data. In an RCTs these confounding factors are evenly distributed across the study groups (assuming randomisation is done correctly), but this is unlikely to be the case in observational research. Because of the presence of confounding factors, observational research cannot prove cause-and-effect. The interest of observational studies lies in revealing these relationships in order to address future research.

The next sections describe three common observational study designs: prospective cohort studies, case-control studies, and cross-sectional studies.

Prospective cohort studies

A prospective cohort study is a study that follows a group of people over time. At the start of the study, researchers ask participants to complete a questionnaire (e.g., about their dietary habits, physical activity levels, etc.) and may also take measurements of weight, height, blood pressure, blood profile or other biological factors. Years later, the researchers look whether the participants have developed disease and study whether exposure from the questionnaire or biological measurements are associated with the disease. 1

One of the main advantages of this design is that researchers observe participants’ natural exposures and behaviours without intervention, providing insights into real-life scenarios. It also allows researchers to examine the long-term effects of nutrition or other lifestyle-related exposures on real diseases. Since chronic diseases, such as heart disease and osteoporosis, often take many decades to develop, a cohort may be more suitable compared to a RCT where often intermediate markers for these diseases are measured (e.g., narrowing of the arteries or bone density). These markers don’t always develop into the disease.

One of the main limitations of cohort studies is that they cannot establish causation definitively due to potential confounding factors. It is also important to consider how participants’ food intake is measured. Cohorts often use what’s called a Food Frequency Questionnaires (FFQs) which measures a person’s average dietary intake over time. While FFQs are one of the best methods available to assess dietary intake, it can be hard to accurately estimate typical intake, portion size, and preparation methods. As data is self-reported, it may include subjective interpretations (e.g., participants may underreport, overreport or simply forgot their past habits: a problem called recall bias). FFQs also don’t represent lifetime behaviour patterns: people may have changed their behaviour over the intervening years (e.g., smokers may quit smoking or meat eaters may become vegetarian), resulting in misclassification of participants and potential bias. When a validated FFQ is used, generally a part of bias is limited.

In a cohort study it is also important that participants are followed up for a long time to accumulate enough data to give robust results. This means they can generally only be used to study diseases that are relatively common. Another concern in cohort studies is selection bias: those selected to be in the study differ from those not selected in some systematic way. Recruitment of participants may be done, for example, through newspapers, phone dialling, the workplace or volunteering, impacting who takes part in the study and how generalisable the results are (i.e., newspapers are often only read by older populations, phone dialling excludes those without phones, volunteering recruits more health-conscious participants, etc.). Another concern occurs if many participants are ‘lost to follow-up’ (i.e., drop out of the study) in one exposure group than another, particularly if loss is also related to the outcome being studied.

Case-control studies

In a case-control study researchers look to the past of people with a disease (called the ‘cases’) and compare it to people without the disease (the ‘controls’). These studies are most often used to study the link between an exposure and a rare outcome. 1 They usually have a smaller sample size than cohort studies and do not require follow-up.

As in cohort studies, recall bias is a problem in case-control studies. This is to even larger extent as people already have the disease of interest when the exposure information is collected or measured and so they might recall their exposure differently from people without disease. Selection bias (cases and/or controls may not be representative for the general population), confounding, and reverse causation can be limitations. Reverse causation occurs when it is challenging to identify if the outcome or exposure came first. For example, if an association was found between the consumption of non-sugar sweeteners and obesity, is this truly because of the higher consumption of non-sugar sweeteners or is it that people with obesity more frequently consumed products containing non-sugar sweeteners to help manage their weight? The choice of an appropriate control group is also one of the main difficulties of this type of study. Control groups should be carefully selected to be similar to the cases (those with the condition of interest) in all aspects except the exposure being studied (e.g., diet). This ensures that any observed difference in outcomes can be attributed to the exposure rather than confounding factors.

Cross-sectional studies

A cross-sectional study is a survey or cross-section of a random sample of the population where information about potential exposures and outcomes is collected at the same time. For example, researchers measure blood pressure and ask questions about, for example, the amount of processed meat each person eats per day. This lets them find out whether there is a link between blood pressure and the amount of processed meat consumed per day. 1

With cross-sectional studies reverse causality is again a problem: you cannot be sure whether eating processed meat affects blood pressure or vice versa, because the information was obtained at the same time. Like cohort studies, they can also be prone to selection and recall bias. Recall bias may be a particular problem, since participant’s knowledge of their health status may influence their reporting of dietary habits (e.g., a person with type 2 diabetes may recall they ate more sweets and sodas than a person without the disease).

Instead, this simple study design can be useful to investigate the possible causes of ill-health at an early stage, examine exposure that do not change over time (e.g., sex, genetic factors) or that occurred many years previously, or estimate the prevalence of dietary habits and health outcomes in a population at a specific time point. They can provide a starting point for further investigation about associations between dietary factors and health outcomes in, for example, a cohort study or RCT.

Animal and cell studies

Animal and cell (or sometimes called in vitro) studies may provide an indication of the likely effect, however, they cannot be directly applied to humans. Research with animals is an important tool in determining how humans may react when exposed to particular substances. However, because of differences in physiology and the fact that animals are routinely exposed to far higher levels of compounds than typical dietary intakes, for example, results cannot be directly applied to humans. 3 Similarly, isolated cells in a laboratory behave differently than cells in our body. For example, if a test tube shows that substance X causes a cell to burn fat faster, that does not mean that substance X will help to lose weight in humans. The human body is much more complex than can be imitated in a test tube.

For research into toxic substances, this type of research is the norm. Testing harmful or possibly toxic compounds on humans is dangerous and unethical. Animal testing is therefore used to establish safety guidelines for chemical compounds such as pesticides and environmental contaminants. Because results cannot be extended to humans and people also differ from each other, wide safety margins are used. However, the use of laboratory animals is being substantially reduced following international protocols such as those by the Organization for Economic Cooperation and Development (OECD). 4

Animal and cell research can complement evidence from observational and experimental research: they can show if there is a mechanism that explains these results. For example, observational research shows that smoking is associated with cancer, while cell studies highlight the specific harmful substances present in tobacco that contributes to the development of cancer. The certainty that a result is accurate increases when there is such a logical explanation.

Anecdotes and case studies

Anecdotes, case reports (on 1 patient) and case series (on several patients) describe a detailed report of individual patient(s) with a specific outcome and/or exposure. 5 They are important for the early identification of health problems and can generate hypotheses about potential causes. However, since they involve a limited number of people, they cannot be generalised to broader populations. A single person’s experience or opinion does not provide an objective picture. Therefore, anecdotes and case studies are regarded as low-quality evidence.

What is considered the ‘best’ evidence?

Generally, the different types of research are organised from single person’s experiences and anecdotes having the weakest certainty of evidence to systematic reviews and meta-analysis having the strongest level of evidence. These levels of evidence can be used as a guideline to judge what can be concluded from a particular study. However, they do not substitute for critical appraisal. 6 For example, a strong cohort study may be more useful than a flawed systematic review. Besides, which type of research scientists choose to conduct depends on, among other things, the research question, the amount of time available and the amount of money. Therefore, evidence may be better sorted by its usefulness for investigating a specific research question than by type of study design.

Different types of study designs should be viewed as complementary. For example, observational research can still be meaningful and illuminating when numerous studies consistently show patterns on a large scale.

RCTs are often regarded as the ‘gold standard’ for conducting research and their findings are believed to be more accurate compared to observational research as they can establish cause-and-effect relationships. However, this assumption is not always valid because the intervention/exposure being studied in RCTs may differ from those in observational studies.6 For example, dietary intakes in observational studies are not interchangeable to some exposures used in RCTs (e.g., intake of omega-3 fatty acids by eating fish is different to omega-3 fatty acids consumed in isolated supplemental form). As a result, it is not surprising that sometimes contradictory results are found between observational and experimental research. 7 When testing findings from observational research further in RCTs, it is therefore important to carefully consider the population being studied, the way the intervention (dietary change) is applied, the comparison group, and the outcome(s) measured. Even small differences in how the study is conducted can lead to varying results.

Nutrition research is expensive and complex to develop. It is therefore difficult to reach to reliable results that support evidence. A single approach is not sufficient. There are a variety of study designs used in nutrition research which are used to study a variety of different exposures and outcomes. How all these studies can lead to a conclusion depends on the certainty of evidence. A link between an exposure and outcome is more certain if: 8

• A large number of prospective cohort studies consistently show an association between exposure to A (cause) and the risk of B (effect);
• The examinations are of good methodological quality, size and duration;
• There are few studies that find the opposite;
• If feasible, experimental studies have also been carried out;
• The link found can be explained biologically.

In contrast, there is insufficient evidence if:

• There are only a small number of studies suggesting that there is a link between exposure to A (cause) and the risk of B (effect);
• The link found is weak;
• No or insufficient experimental and observational studies have been done and therefore more research is needed.

• Webb P, Bain C & Page A (2017) Essential epidemiology: an introduction for students and health professionals. Cambridge University Press.
• PRISMA. (2023). Transparent reporting of systematic reviews and meta-analyses. Retrieved from http://www.prisma-statement.org/?AspxAutoDetectCookieSupport=1 (Accessed 05/09/2023)
• Van der Worp HB et al. (2010) Can animal models of disease reliably inform human studies? PLoS Medicine, 7(3):e1000245.
• OECD. (2023). Animal Welfare. Retrieved from https://www.oecd.org/chemicalsafety/testing/animal-welfare.htm (Accessed 05/09/2023)
• Mathes T & Pieper D (2017) Clarifying the distinction between case series and cohort studies in systematic reviews of comparative studies: potential impact on body of evidence and workload. BMC medical research methodology, 17:1-6.
• Flanagan A et al. (2023). Need for a nutrition-specific scientific paradigm for research quality improvement. BMJ Nutrition, Prevention & Health e000650
• Schwingshackl L et al. (2021) Evaluating agreement between bodies of evidence from randomised controlled trials and cohort studies in nutrition research: meta-epidemiological study. British Medical Journal 374:n1864.
• World Health Organization. (2014). WHO Handbook for Guideline Development. 2nd edition. Retrieved from https://www.who.int/publications/i/item/9789241548960 (Accessed 02/08/2023)

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Clinical Nutrition Case Study: 3 must-ask questions

If you’re struggling to figure out answers to your clinical nutrition case study or if you’re having trouble working through patient care in real life, keep reading. These 3 questions are for you.

Clinical nutrition case studies are hard.

They have a lot of moving parts and (if they’re anything like patients you’ll see in the real world), don’t always have obvious answers to simple questions.

If you’re struggling to figure out answers to your clinical case studies or if you’re having trouble working through patient care in real life, keep reading.

You’re going to start with these 3 questions every time you’re handed a new patient.

What are the 3 steps in a nutrition intervention

Before we talk about the 3 questions you’ll use every time you start a new clinical nutrition case study, let’s talk about the standard nutrition intervention format.

You probably already know the 3 steps to use in a nutrition intervention. They look like this:

• Intervention

However I’ve found that taking the words assessment, diagnosis and intervention at face value, can be kind of confusing.

And if you aren’t sure where different patient issues fall into these categories, it’s going to be much harder to work through clinical nutrition case studies.

So you’re going to stop trying to figuring out if what you’re looking at falls into the assessment, diagnosis or intervention category, we’re going to make it much easier.

Instead, you’re going to ask yourself 3 simple questions that will make sure you’re thinking clearly about all the available information you have.

How to do a clinical nutrition case study with 3 question

These are the 3 questions you’ll answer during every clinical nutrition case study you’re given. These are also the same questions you should be asking with any patient you see in the real world.

Here are the 3 questions to ask yourself every time you’re looking at patient in clinical nutrition for the first time :

• What do you know?
• What are you most concerned about?
• What are your next steps?

Each of these questions will focus your attention on what information you have, what is most important and what you’re missing.

If these 3 questions sound a lot like the way you do a nutrition intervention, you’re right.

What do you know is the assessment . What are you most concerned about is the diagnosis . And what are your next steps is the intervention .

Thinking about each of the 3 parts of the nutrition intervention this way make it much easier to understand figure out the most acute nutritional issue of your patient.

And from there, understand how you can support them in improving their nutritional health.

The point of doing a clinical nutrition case study

Ultimately your goal is always to answer a single question:

What’s the one thing I can do right now to improve this person’s health as quickly as possible?

The answer to that is  your patient’s most acute nutritional issue.

And once you know their most acute nutritional issue, you’ll know how to form your PES statement and what to focus on in your nutrition note or care plan.

So let’s talk specifics.

What do each of these questions mean? And how are you going to use them to determine the most acute nutritional issue as you think through your clinical nutrition case study?

The 3 questions to answer in during a clinical nutrition case study

Question #1: what do you know.

This is the first question you’re going to ask yourself when you’re handed a clinical nutrition case study. But keep in mind, these work for real life patients too.

Write down every piece of information that seems nutritionally relevant. That includes:

• Diagnoses: admitting and PMH
• Weight status

Question #2: What are you most concerned about?

This is where you filter that list into the things that impacting your patient’s health status. 

Some of the things on this list will be not worry you at all. The lab work might be normal. Your patient’s weight status might be within normal limits. Maybe they have no significant past medical history.

On the other hand, you might be worried about everything on the list. Clinical nutrition case studies can be either overly simple or ridiculously complex.

Whatever stands out to you, highlight it. All of it.

These are the items that will form the basis of your nutrition assessment and intervention.

Question #3: What are your next steps?

There are 2 possible ways the answer to this question can go.

• You have all the information you need.
• You are missing information.

If you have everything you need and you have no more questions, you’re done. Wrap up your clinical nutrition case study by summarizing the important points that you’ve pulled together with questions 1 and 2.

Write you nutrition note and move on.

But if you need to find out more information, it’s time to make a list of what you just learned. Then start reviewing these 3 questions again, from the top. 

More information might need to come from a doctor , looking up something new in the medical chart or by asking your patient a direct question. 

Each of these sources have the power to dramatically shift the way you support your patient. And if that happens, you want to take the time to revise your nutrition care plan to better meet those new needs.

And That’s It!

Clinical nutrition in the real world, just like clinical nutrition case studies, is all about using all available information to give your patient the best possible chance at positive health outcomes. 

To make that happen these are the 3 questions you’re going to ask yourself. On repeat. Until you are confident of you can help them get discharged as quickly as possible.

Feel like this was cool, but you’ve got specific questions? I got you. Clinical Text Support is your chance to ask every question you have, as they come up in real time. Maybe it’s working through a crazy case study. It could also be real patients you’re assigned in your clinical rotations. In Clinical Text Support, you get immediate answers to the questions you might not want to ask a preceptor or teacher.

Need even more? I hear you. Clinical Bootcamp is everything you need to do clinical nutrition in the real world. It’s exactly the clinical nutrition course you thought you’d get in school, but never did. After Bootcamp, you’ll know how to not only work through every patient care situation — but you’ll be doing it confidently. Every time.

Want even more to help in clinical? Check out The Nutrition Cheat Sheets Shop for all the nutrition education and clinical resources that will make your life easier.

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Use Case Studies to Bring Life Into Your Nutrition Course

NutritionCalc Case studies are a helpful way for students to bring life to the information in their textbook and Connect offers a variety of different topics to be used in your class.

Case Studies are great as a stand-alone project but they can also be built into assignments or even expanded upon in a variety of ways.  No matter how you use the case studies your students will gain a deeper understanding of the topic while increasing their critical thinking skills.

Here are a couple of ways you can use the auto-graded Case Study assignment in your classroom, whether virtual or in seated class.

Alternative to a personal 3-day record

A case study can be an alternative assignment for students who feel uncomfortable analyzing their diet and/or have a history of an eating disorder. The case study takes the focus off analyzing a personal record.

If needed, you can adjust the questions to focus more on the quality of the diet versus analyzing numbers like calories or grams of protein etc. You could also add more open-ended questions that include students looking for recipes that are suitable for that case study scenario.

Delve deeper to spark conversation into the topic

Use the case studies as an opportunity to have your students delve deeper into the topic with a discussion. If your students are in person, you can have them work in small groups and then discuss the case study. Alternatively, an online class may use discussion boards.

For example, the case study “Staying Energized When Stressed” could be a great case study to have at the beginning of the semester. This case study is a good starting point for students to bring self-awareness and begin to make connections with how college life can impact their eating habits.

Combine with another assignment

Each case study has 10 auto-graded questions that can be an excellent addition to an assignment you already have.

A nutrition article review assignment where students analyze the credibility of the article’s information can be a nice complement to many of the different case studies in Connect. By having an article review at the start of the assignment and then ending with a case study students can better demonstrate understanding and comprehension of the topic.

Add an AI menu planning feature

Take the case study one step further by incorporating a meal plan that is created using AI. Artificial intelligence will not always be accurate but one of the cool things about it is that it can create sample meal plans.

AI platforms can quickly create meal plans for various concerns or medical conditions; the accuracy of these plans is another story. Use an AI meal plan as a learning moment for students.

For example, assign the Polycystic Ovary Syndrome case study and then add an open-ended question where you instruct students to create an AI-generated meal plan. You can have the students write in their thoughts on the accuracy and feasibility of the meal plan. For your in-seat classes, you could have them bring their laptops and discuss in a small group.

Available Case Studies in NutritionCalc Plus: Nutrient Density, Keto Diet, Dietary Guidelines, Whole vs. Refined Grains, Diabetes, Mediterranean Diet, High Protein Diet, Vegan Dietary Pattern, DASH Diet, Weight Management, 5,000-calorie Diet, Breastfeeding Diet, School-Age Dietary Pattern, Okinawan Diet, WIC, Bone Health, Female Athlete Triad RED-S, Constipation.

New Cases coming Summer 2024: Celiac Disease, Elderly, Irritable Bowel Syndrome, Polycystic Ovary Syndrome, Fermented/Probiotic Foods, Heart Health, Anemia, Supporting Detox, Staying Energized when Stressed, Metabolic Support.

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2.3: Types of Research Studies and How To Interpret Them

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• Alice Callahan, Heather Leonard, & Tamberly Powell
• Lane Community College via OpenOregon

The field of nutrition is dynamic, and our understanding and practices are always evolving. Nutrition scientists are continuously conducting new research and publishing their findings in peer-reviewed journals. This adds to scientific knowledge, but it’s also of great interest to the public, so nutrition research often shows up in the news and other media sources. You might be interested in nutrition research to inform your own eating habits, or if you work in a health profession, so that you can give evidence-based advice to others. Making sense of science requires that you understand the types of research studies used and their limitations.

The Hierarchy of Nutrition Evidence

Researchers use many different types of study designs depending on the question they are trying to answer, as well as factors such as time, funding, and ethical considerations. The study design affects how we interpret the results and the strength of the evidence as it relates to real-life nutrition decisions. It can be helpful to think about the types of studies within a pyramid representing a hierarchy of evidence, where  the  studies at the bottom of the pyramid usually give us the weakest evidence with the least relevance to real-life nutrition decisions, and the studies at the top offer the strongest evidence, with the most relevance to real-life nutrition  decisions .

The pyramid also represents a few other general ideas. There tend to be more studies published using the methods at the bottom of the pyramid, because they require less time, money, and other resources. When researchers want to test a new hypothesis , they often start with the study designs at the bottom of the pyramid , such as in vitro, animal, or observational studies. Intervention studies are more expensive and resource-intensive, so there are fewer of these types of studies conducted. But they also give us higher quality evidence, so they’re an important next step if observational and non-human studies have shown promising results. Meta-analyses and systematic reviews combine the results of many studies already conducted, so they help researchers summarize scientific knowledge on a topic.

Non-Human Studies: In Vitro & Animal Studies

The simplest form of nutrition research is an in vitro study . In vitro means “within glass,” (although plastic is used more commonly today) and these experiments are conducted within flasks, dishes, plates, and test tubes. These studies are performed on isolated cells or tissue samples, so they’re less expensive and time-intensive than animal or human studies. In vitro studies are vital for zooming in on biological mechanisms, to see how things work at the cellular or molecular level. However, these studies shouldn’t be used to draw conclusions about how things work in humans (or even animals), because we can’t assume that the results will apply to a whole, living organism.

Animal studies are one form of in vivo research, which translates to “within the living.” Rats and mice are the most common animals used in nutrition research. Animals are often used in research that would be unethical to conduct in humans. Another advantage of animal dietary studies is that researchers can control exactly what the animals eat. In human studies, researchers can tell subjects what to eat and even provide them with the food, but they may not stick to the planned diet. People are also not very good at estimating, recording, or reporting what they eat and in what quantities. In addition, animal studies typically do not cost as much as human studies.

There are some important limitations of animal research. First, an animal’s metabolism and physiology are different from humans. Plus, animal models of disease (cancer, cardiovascular disease, etc.), although similar, are different from human diseases. Animal research is considered preliminary, and while it can be very important to the process of building scientific understanding and informing the types of studies that should be conducted in humans, animal studies shouldn’t be considered relevant to real-life decisions about how people eat.

Observational Studies

Observational studies  in human nutrition collect information on people’s dietary patterns or nutrient intake and look for associations with health outcomes. Observational studies do not give participants a treatment or intervention; instead, they look at what they’re already doing and see how it relates to their health. These types of study designs can only identify  correlations  (relationships) between nutrition and health; they can’t show that one factor  causes  another. (For that, we need intervention studies, which we’ll discuss in a moment.) Observational studies that describe factors correlated with human health are also called  epidemiological studies . 1

One example of a nutrition hypothesis that has been investigated using observational studies is that eating a Mediterranean diet reduces the risk of developing cardiovascular disease. (A Mediterranean diet focuses on whole grains, fruits and vegetables, beans and other legumes, nuts, olive oil, herbs, and spices. It includes small amounts of animal protein (mostly fish), dairy, and red wine. 2 ) There are three main types of observational studies, all of which could be used to test hypotheses about the Mediterranean diet:

• Cohort studies follow a group of people (a cohort) over time, measuring factors such as diet and health outcomes. A cohort study of the Mediterranean diet would ask a group of people to describe their diet, and then researchers would track them over time to see if those eating a Mediterranean diet had a lower incidence of cardiovascular disease.
• Case-control studies compare a group of cases and controls, looking for differences between the two groups that might explain their different health outcomes. For example, researchers might compare a group of people with cardiovascular disease with a group of healthy controls to see whether there were more controls or cases that followed a Mediterranean diet.
• Cross-sectional studies collect information about a population of people at one point in time. For example, a cross-sectional study might compare the dietary patterns of people from different countries to see if diet correlates with the prevalence of cardiovascular disease in the different countries.

Prospective cohort studies, which enroll a cohort and follow them into the future, are usually considered the strongest type of observational study design. Retrospective studies look at what happened in the past, and they’re considered weaker because they rely on people’s memory of what they ate or how they felt in the past. There are several well-known examples of prospective cohort studies that have described important correlations between diet and disease:

• Framingham Heart Study : Beginning in 1948, this study has followed the residents of Framingham, Massachusetts to identify risk factors for heart disease.
• Health Professionals Follow-Up Study : This study started in 1986 and enrolled 51,529 male health professionals (dentists, pharmacists, optometrists, osteopathic physicians, podiatrists, and veterinarians), who complete diet questionnaires every 2 years.
• Nurses Health Studies : Beginning in 1976, these studies have enrolled three large cohorts of nurses with a total of 280,000 participants. Participants have completed detailed questionnaires about diet, other lifestyle factors (smoking and exercise, for example), and health outcomes.

Observational studies have the advantage of allowing researchers to study large groups of people in the real world, looking at the frequency and pattern of health outcomes and identifying factors that correlate with them. But even very large observational studies may not apply to the population as a whole. For example, the Health Professionals Follow-Up Study and the Nurses Health Studies include people with above-average knowledge of health. In many ways, this makes them ideal study subjects, because they may be more motivated to be part of the study and to fill out detailed questionnaires for years. However, the findings of these studies may not apply to people with less baseline knowledge of health.

We’ve already mentioned another important limitation of observational studies—that they can only determine correlation, not causation. A prospective cohort study that finds that people eating a Mediterranean diet have a lower incidence of heart disease can only show that the Mediterranean diet is correlated with lowered risk of heart disease. It can’t show that the Mediterranean diet directly prevents heart disease. Why? There are a huge number of factors that determine health outcomes such as heart disease, and other factors might explain a correlation found in an observational study. For example, people who eat a Mediterranean diet might also be the same kind of people who exercise more, sleep more, have higher income (fish and nuts can be expensive!), or be less stressed. These are called confounding factors ; they’re factors that can affect the outcome in question (i.e., heart disease) and also vary with the factor being studied (i.e., Mediterranean diet).

Intervention Studies

Intervention studies , also sometimes called experimental studies or clinical trials, include some type of treatment or change imposed by the researcher. Examples of interventions in nutrition research include asking participants to change their diet, take a supplement, or change the time of day that they eat. Unlike observational studies, intervention studies can provide evidence of cause and effect , so they are higher in the hierarchy of evidence pyramid.

The gold standard for intervention studies is the randomized controlled trial (RCT) . In an RCT, study subjects are recruited to participate in the study. They are then randomly assigned into one of at least two groups, one of which is a control group (this is what makes the study controlled ). In an RCT to study the effects of the Mediterranean diet on cardiovascular disease development, researchers might ask the control group to follow a low-fat diet (typically recommended for heart disease prevention) and the intervention group to eat a Mediterrean diet. The study would continue for a defined period of time (usually years to study an outcome like heart disease), at which point the researchers would analyze their data to see if more people in the control or Mediterranean diet had heart attacks or strokes. Because the treatment and control groups were randomly assigned, they should be alike in every other way except for diet, so differences in heart disease could be attributed to the diet. This eliminates the problem of confounding factors found in observational research, and it’s why RCTs can provide evidence of causation, not just correlation.

Imagine for a moment what would happen if the two groups weren’t randomly assigned. What if the researchers let study participants choose which diet they’d like to adopt for the study? They might, for whatever reason, end up with more overweight people who smoke and have high blood pressure in the low-fat diet group, and more people who exercised regularly and had already been eating lots of olive oil and nuts for years in the Mediterranean diet group. If they found that the Mediterranean diet group had fewer heart attacks by the end of the study, they would have no way of knowing if this was because of the diet or because of the underlying differences in the groups. In other words, without randomization, their results would be compromised by confounding factors, with many of the same limitations as observational studies.

In an RCT of a supplement, the control group would receive a placebo—a  “fake” treatment that contains no active ingredients, such as a sugar pill. The use of a placebo is necessary in medical research because of a phenomenon known as the placebo effect. The placebo effect results in a beneficial effect because of a subject’s belief in the treatment, even though there is no treatment actually being administered.

Blinding is a technique to prevent bias in intervention studies. In a study without blinding, the subject and the researchers both know what treatment the subject is receiving. This can lead to bias if the subject or researcher have expectations about the treatment working, so these types of trials are used less frequently. It’s best if a study is double-blind , meaning that neither the researcher nor the subject know what treatment the subject is receiving. It’s relatively simple to double-blind a study where subjects are receiving a placebo or treatment pill, because they could be formulated to look and taste the same. In a single-blind study , either the researcher or the subject knows what treatment they’re receiving, but not both. Studies of diets—such as the Mediterranean diet example—often can’t be double-blinded because the study subjects know whether or not they’re eating a lot of olive oil and nuts. However, the researchers who are checking participants’ blood pressure or evaluating their medical records could be blinded to their treatment group, reducing the chance of bias.

Like all studies, RCTs and other intervention studies do have some limitations. They can be difficult to carry on for long periods of time and require that participants remain compliant with the intervention. They’re also costly and often have smaller sample sizes. Furthermore, it is unethical to study certain interventions. (An example of an unethical intervention would be to advise one group of pregnant mothers to drink alcohol to determine its effects on pregnancy outcomes, because we know that alcohol consumption during pregnancy damages the developing fetus.)

VIDEO: “ Not all scientific studies are created equal ” by David H. Schwartz, YouTube (April 28, 2014), 4:26.

Meta-Analyses and Systematic Reviews

At the top of the hierarchy of evidence pyramid are systematic reviews and meta-analyses .  You can think of these as “studies of studies.” They attempt to combine all of the relevant studies that have been conducted on a research question and summarize their overall conclusions. Researchers conducting a  systematic review  formulate a research question and then systematically and independently identify, select, evaluate, and synthesize all high-quality evidence that relates to the research question. Since systematic reviews combine the results of many studies, they help researchers produce more reliable findings. A  meta-analysis  is a type of systematic review that goes one step further, combining the data from multiple studies and using statistics to summarize it, as if creating a mega-study from many smaller studies . 4

However, even systematic reviews and meta-analyses aren’t the final word on scientific questions. For one thing, they’re only as good as the studies that they include. The  Cochrane Collaboration  is an international consortium of researchers who conduct systematic reviews in order to inform evidence-based healthcare, including nutrition, and their reviews are among the most well-regarded and rigorous in science. For the most recent Cochrane review of the Mediterranean diet and cardiovascular disease, two authors independently reviewed studies published on this question. Based on their inclusion criteria, 30 RCTs with a total of 12,461 participants were included in the final analysis. However, after evaluating and combining the data, the authors concluded that “despite the large number of included trials, there is still uncertainty regarding the effects of a Mediterranean‐style diet on cardiovascular disease occurrence and risk factors in people both with and without cardiovascular disease already.” Part of the reason for this uncertainty is that different trials found different results, and the quality of the studies was low to moderate. Some had problems with their randomization procedures, for example, and others were judged to have unreliable data. That doesn’t make them useless, but it adds to the uncertainty about this question, and uncertainty pushes the field forward towards more and better studies. The Cochrane review authors noted that they found seven ongoing trials of the Mediterranean diet, so we can hope that they’ll add more clarity to this question in the future. 5

Science is an ongoing process. It’s often a slow process, and it contains a lot of uncertainty, but it’s our best method of building knowledge of how the world and human life works. Many different types of studies can contribute to scientific knowledge. None are perfect—all have limitations—and a single study is never the final word on a scientific question. Part of what advances science is that researchers are constantly checking each other’s work, asking how it can be improved and what new questions it raises.

Attributions:

• “Chapter 1: The Basics” from Lindshield, B. L. Kansas State University Human Nutrition (FNDH 400) Flexbook. goo.gl/vOAnR , CC BY-NC-SA 4.0
• “ The Broad Role of Nutritional Science ,” section 1.3 from the book An Introduction to Nutrition (v. 1.0), CC BY-NC-SA 3.0

References:

• 1 Thiese, M. S. (2014). Observational and interventional study design types; an overview. Biochemia Medica , 24 (2), 199–210. https://doi.org/10.11613/BM.2014.022
• 2 Harvard T.H. Chan School of Public Health. (2018, January 16). Diet Review: Mediterranean Diet . The Nutrition Source. https://www.hsph.harvard.edu/nutritionsource/healthy-weight/diet-reviews/mediterranean-diet/
• 3 Ross, R., Gray, C. M., & Gill, J. M. R. (2015). Effects of an Injected Placebo on Endurance Running Performance. Medicine and Science in Sports and Exercise , 47 (8), 1672–1681. https://doi.org/10.1249/MSS.0000000000000584
• 4 Hooper, A. (n.d.). LibGuides: Systematic Review Resources: Systematic Reviews vs Other Types of Reviews . Retrieved February 7, 2020, from //libguides.sph.uth.tmc.edu/c.php?g=543382&p=5370369
• 5 Rees, K., Takeda, A., Martin, N., Ellis, L., Wijesekara, D., Vepa, A., Das, A., Hartley, L., & Stranges, S. (2019). Mediterranean‐style diet for the primary and secondary prevention of cardiovascular disease. Cochrane Database of Systematic Reviews , 3 . doi.org/10.1002/14651858.CD009825.pub3
• Figure 2.3. The hierarchy of evidence by Alice Callahan, is licensed under CC BY 4.0
• Research lab photo by National Cancer Institute on Unsplas h ; mouse photo by vaun0815 on Unsplash
• Figure 2.4. “Placebo effect example” by Lindshield, B. L. Kansas State University Human Nutrition (FNDH 400) Flexbook. goo.gl/vOAnR

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Defining a Healthy Diet: Evidence for the Role of Contemporary Dietary Patterns in Health and Disease

Hellas cena.

1 Laboratory of Dietetics and Clinical Nutrition, Department of Public Health, Experimental and Forensic Medicine, University of Pavia, 27100 Pavia, Italy

2 Clinical Nutrition and Dietetics Service, Unit of Internal Medicine and Endocrinology, ICS Maugeri IRCCS, 27100 Pavia, Italy

Philip C. Calder

3 Human Development and Health, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK

4 NIHR Southampton Biomedical Research Centre, University Hospital Southampton NHS Foundation Trust and University of Southampton, Southampton SO16 6YD, UK

The definition of what constitutes a healthy diet is continually shifting to reflect the evolving understanding of the roles that different foods, essential nutrients, and other food components play in health and disease. A large and growing body of evidence supports that intake of certain types of nutrients, specific food groups, or overarching dietary patterns positively influences health and promotes the prevention of common non-communicable diseases (NCDs). Greater consumption of health-promoting foods and limited intake of unhealthier options are intrinsic to the eating habits of certain regional diets such as the Mediterranean diet or have been constructed as part of dietary patterns designed to reduce disease risk, such as the Dietary Approaches to Stop Hypertension (DASH) or Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diets. In comparison with a more traditional Western diet, these healthier alternatives are higher in plant-based foods, including fresh fruits and vegetables, whole grains, legumes, seeds, and nuts and lower in animal-based foods, particularly fatty and processed meats. To better understand the current concept of a “healthy diet,” this review describes the features and supporting clinical and epidemiologic data for diets that have been shown to prevent disease and/or positively influence health. In total, evidence from epidemiological studies and clinical trials indicates that these types of dietary patterns reduce risks of NCDs including cardiovascular disease and cancer.

1. Introduction

Non-communicable diseases (NCDs) such as cardiovascular disease, cancer, chronic respiratory diseases, diabetes, obesity, and cognitive impairment are among the leading causes of death and disability throughout the world, affecting populations in developed as well as developing countries [ 1 ]. Although there are established genetic and environmental contributors to NCD risk, modifiable lifestyle-related factors play a large role at the individual level [ 2 , 3 , 4 ]. Dietary choices, for example, contribute to the risk for developing hypertension, hypercholesterolemia, overweight/obesity, and inflammation, which in turn increase the risk for diseases that are associated with significant morbidity and mortality, including cardiovascular disease, diabetes, and cancer [ 5 ]. Indeed, the marked rise in chronic NCDs has a causal link to global dietary patterns that are becoming increasingly Westernized [ 6 ], being characterized by high levels of fatty and processed meats, saturated fats, refined grains, salt, and sugars but lacking in fresh fruits and vegetables.

In recognition of the importance of the diet as a determinant of disease risk, the World Health Organization (WHO) Global Action Plan for the Prevention and Control of Noncommunicable Diseases includes strategies for addressing unhealthy diet patterns among its initiatives directed at reducing behavioral risk factors; the other components comprise physical inactivity, tobacco use, and harmful alcohol use [ 1 ]. Dietary changes recommended by WHO include balancing energy intake, limiting saturated and trans fats and shifting toward consumption of unsaturated fats, increasing intake of fruits and vegetables, and limiting the intake of sugar and salt. Many of these dietary targets naturally occur in regional diets such as the Mediterranean diet [ 7 ] or are included as part of evidence-based diets designed to reduce disease risk, such as the Dietary Approaches to Stop Hypertension (DASH) [ 8 ] or Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) [ 9 ] diets. To better understand the current concept of a “healthy diet”, this narrative review describes the features and supporting clinical and epidemiologic data for diets that align with the general WHO guidance and have been shown to prevent disease and/or positively influence health.

2. Components of a Healthy Diet and Their Benefits

A healthy diet is one in which macronutrients are consumed in appropriate proportions to support energetic and physiologic needs without excess intake while also providing sufficient micronutrients and hydration to meet the physiologic needs of the body [ 10 ]. Macronutrients (i.e., carbohydrates, proteins, and fats) provide the energy necessary for the cellular processes required for daily functioning [ 11 ]. Micronutrients (i.e., vitamins and minerals) are required in comparatively small amounts for normal growth, development, metabolism, and physiologic functioning [ 12 , 13 ].

Carbohydrates are the primary source of energy in the diet and are found in the greatest abundance in grains, fruits, legumes, and vegetables [ 14 ]. In terms of deriving a health benefit, whole grains are preferred over processed grains, the latter having been stripped of germ and bran during the milling process, resulting in lower amounts of fiber and micronutrients [ 15 ]. Meta-analyses of prospective cohort studies have linked increased whole-grain intake to a reduced risk of coronary heart disease, stroke, cardiovascular disease, and cancer, as well as to the decreased risk of mortality due to any cause, cardiovascular disease, cancer, respiratory disease, diabetes, and infectious disease [ 15 , 16 , 17 ]. Fresh fruits and vegetables supply energy as well as dietary fiber, which promotes the feeling of satiety and has positive effects on gastrointestinal function, cholesterol levels, and glycemic control [ 18 ]. In addition, fresh fruits and vegetables are key sources of phytochemicals (e.g., polyphenols, phytosterols, carotenoids), which are bioactive compounds believed to confer many of the health benefits associated with fruit and vegetable consumption [ 19 ]. The mechanistic effects of these various phytochemicals are unclear but include their antioxidative properties, as well as their role in regulating nuclear transcription factors, fat metabolism, and inflammatory mediators. For example, flavonoids have been shown to increase insulin secretion and reduce insulin resistance, suggesting that these phytochemicals provide some benefits in obesity and diabetes [ 20 ]. Additionally, polyphenols interact with gastrointestinal microbiota in a bi-directional manner by enhancing gut bacteria and being metabolized by these bacteria to form more bioactive compounds [ 20 ]. Fruit and vegetable intake has been shown to inversely correlate with the risk of NCDs, including hypertension [ 21 ], cardiovascular disease [ 22 , 23 ], chronic obstructive pulmonary disease [ 24 ], lung cancer [ 25 ], and metabolic syndrome [ 26 ].

Dietary proteins provide a source of energy as well as amino acids, including those that the human body requires but cannot produce on its own (i.e., essential amino acids). Dietary proteins are derived from both animal (meat, dairy, fish, and eggs) and plant (legumes, soya products, grains, nuts, and seeds) sources, with the former considered a richer source due to the array of amino acids, high digestibility, and greater bioavailability [ 27 ]. However, animal-based sources of protein contain saturated fatty acids, which have been linked to cardiovascular disease, dyslipidemia, and certain cancers. Although the mechanisms are unclear, red meat, and processed meat in particular, have been associated with an increased risk of colorectal cancer [ 28 , 29 ]. Animal-derived proteins also increase the dietary acid load, tipping the body’s acid-base balance toward acidosis [ 30 , 31 ]. The increased metabolic acid load has been linked to insulin resistance, impaired glucose homeostasis, and the development of urinary calcium stones [ 30 , 31 ].

Adequate dietary protein intake is important for maintaining lean body mass throughout the life span. In older adults, protein plays an important role in preventing age-related loss of skeletal muscle mass [ 32 ], preserving bone mass, and reducing fracture risk [ 33 ]. For older individuals not obtaining adequate protein from their diets, supplementation with amino acids can improve strength and functional status [ 34 ].

Fats (or lipids) are the primary structural components of cellular membranes and are also sources of cellular energy [ 35 ]. Dietary fats fall into 4 categories: monounsaturated fats, polyunsaturated fats, saturated fats, and trans fats. The fat content of food is generally an admixture of these different types [ 35 ]. Unsaturated fats are found in a variety of foods, including fish, many plant-derived oils, nuts, and seeds, whereas animal products (and some plant-derived oils) contribute a larger proportion of saturated fats [ 35 , 36 ]. Trans fats found in foods are predominantly the result of processing vegetable oils but are also present in small quantities in animal products (i.e., ruminant trans fats from cows, sheep, and goats) [ 35 , 36 ]. Among the types of dietary fats, unsaturated fats are associated with reduced cardiovascular and mortality risks, whereas trans fats and, to a lesser degree, saturated fats are associated with negative impacts on health, including increased mortality risk [ 36 , 37 ]. Two families of polyunsaturated fatty acids, omega-3 and omega-6, are described as essential fatty acids, because they are required for normal growth and reproduction but are not produced by the body and, therefore, must be obtained from dietary sources [ 10 ]. Omega-3 fatty acids, in particular, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), have been widely studied for their potential health benefits, with evidence suggesting positive effects including cardioprotection, preventing cognitive decline, reducing inflammation, sustaining muscle mass, and improving systemic insulin resistance [ 38 , 39 , 40 ]. Seafood, especially oily fish, provides EPA and DHA, and supplements are widely available for those not meeting recommended intakes with diet alone [ 41 , 42 ]. Nuts and some seeds and plant oils provide alpha-linolenic acid, the major plant omega-3 fatty acid [ 43 ].

Although required in trace amounts compared with macronutrients, micronutrients are necessary for normal growth, metabolism, physiologic functioning, and cellular integrity [ 12 , 13 ]. The shift from whole foods to processed, refined foods has reduced the micronutrient quality of the modern Western diet [ 44 ]. Vitamin and mineral inadequacies have been implicated in cellular aging and late-onset disease, as scarcity drives chronic metabolic disruption. Keeping with these observations, adequate dietary intake of, or supplementation with, micronutrients that have antioxidant properties (e.g., vitamins A, C, and E, copper, zinc, and selenium) has been suggested as a means to reduce the risk for and progression of age-related diseases [ 45 ].

Water is the principal component of the body, constituting the majority of lean body mass and total body weight [ 13 ]. Water not only provides hydration but also carries micronutrients, including trace elements and electrolytes [ 46 , 47 ]. Drinking water may supply as much as 20% of the daily recommended intake of calcium and magnesium [ 47 ]. Our understanding of water requirements and water’s effect on health and disease is limited, although the global increase in intake of high-calorie beverages has refocused attention on the importance of water for maintaining health and preventing disease [ 46 ].

3. Common Health-Promoting Dietary Patterns

Based on our understanding of nutritional requirements and their likely health impacts as described above, healthy dietary patterns can be generally described as those that are rich in health-promoting foods, including plant-based foods, fresh fruits and vegetables, antioxidants, soya, nuts, and sources of omega-3 fatty acids, and low in saturated fats and trans fats, animal-derived proteins, and added/refined sugars [ 48 ]. Patterns such as these are naturally occurring in certain regions of the world and rooted in local/regional tradition and food sources, as is the case for the traditional Mediterranean and Asian diets. Healthy dietary patterns have also been developed based on studies of nutrient intake and subsequent health measures or outcomes (e.g., the DASH [ 8 ] and MIND [ 9 ] diets) that share some common characteristics ( Figure 1 ).

A generalized healthy diet and lifestyle pyramid.

3.1. Mediterranean Diet

The Mediterranean diet is based on components of the traditional dietary patterns of Euro-Mediterranean countries and encompasses not only the types of foods consumed and their relative contributions to daily nutrient intake, but also an approach to eating that is cognizant of how foods are sourced (e.g., sustainability and eco-friendliness), cooked, and eaten, as well as lifestyle considerations such as engaging in regular physical activity, getting adequate rest, and participating in fellowship when preparing and sharing meals [ 7 ]. Within the core framework of the Mediterranean diet, variations based on geography and culture are reflected in the emphasis on the inclusion of traditional and local food products. The primary basis of daily meals in the Mediterranean diet is cereals such as whole-grain bread, pastas, couscous, and other unrefined grains that are rich in fiber and a variety of fruits and vegetables of different colors and textures that are high in micronutrients, fiber, and phytochemicals ( Table 1 ) [ 7 , 9 , 49 , 50 , 51 , 52 ]. Dairy products, preferably low-fat yogurt, cheese, or other fermented dairy products, are recommended daily in moderation as a source of calcium, which is needed for bone and heart health. Olive oil serves as the primary source of dietary lipids and is supplemented with olives, nuts, and seeds. Water (1.5–2.0 L/day or ~8 glasses) is recommended as the main source of hydration, whereas wine and other fermented alcoholic beverages are generally permitted in moderation, to be consumed with meals. Fish, white meat, and eggs are the primary sources of protein; red meat and processed meats are consumed less frequently and in smaller portions. Legumes are also a preferred source of plant-based proteins [ 7 ].

Comparison of nutritional/lifestyle components among different healthy diet options.

a Recommendations shown here are based on a 2000 calorie per day eating plan. b Contribution of total fat and quality of fat from cheese to stay within the recommended daily intake.

The health benefits of the Mediterranean diet were first described in 1975 by Ancel Keys, who observed a reduction in cardiovascular disease risk among populations whose nutritional model was consistent with practices of peoples from the Mediterranean Basin [ 53 ]. Since that time, research has revealed beneficial effects of the Mediterranean diet on a number of NCDs and related health measures, including cardiovascular and cerebrovascular disease [ 54 ], cancer [ 55 ], glycemic control [ 56 ], and cognitive function [ 57 , 58 ]. Although publication of a key intervention study (Prevención con Dieta Mediterránea; PREDIMED) conducted at multiple sites across Spain and evaluating the Mediterranean diet for the primary prevention of cardiovascular disease was retracted due to irregularities in randomization [ 59 ], a subsequent analysis adjusting for these issues reported a consistent positive effect of adhering to a Mediterranean diet supplemented with olive oil or nuts compared with a reduced-fat diet [ 59 ]. Substudies of PREDIMED have also shown that, compared with a low-fat control diet, the Mediterranean diet supplemented with olive oil or nuts is associated with a 30% reduced risk of major cardiovascular risk events [ 59 ] and reductions in systolic blood pressure (SBP) and diastolic blood pressure (DBP) of 5.8–7.3 mmHg and 3.3–3.4 mmHg, respectively [ 60 ]. In addition, cardiovascular factors such as mean internal carotid artery intima-media thickness (−0.084 mm; p < 0.05) and maximum plaque height (−0.091 mm; p < 0.05) are improved with the Mediterranean diet supplemented with nuts [ 61 ]. Greater intake of polyphenols (phytochemicals found in fruits, vegetables, tea, olive oil, and wine) correlated with a 36% reduced risk of hypertension ( p = 0.015) [ 62 ] and improvements in inflammatory biomarkers related to atherosclerosis (i.e., interleukin [IL]-6, tumor necrosis factor-alpha, soluble intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and monocyte chemotactic protein-1; p < 0.05 for each), as well as in high-density lipoprotein cholesterol (HDL-C; p = 0.004) [ 62 , 63 ].

3.2. Dietary Approaches to Stop Hypertension (DASH)

The DASH diet derives its name from the Dietary Approaches to Stop Hypertension study, which evaluated the influence of dietary patterns on blood pressure [ 8 ]. Patients who consumed a diet that was rich in fruits, vegetables, and low-fat dairy and that included a reduced amount of saturated and total fat and cholesterol experienced significantly greater reductions in blood pressure than patients who consumed a control diet that was similar in composition to a typical American diet (difference in SBP/DBP, −5.5/−3.0 mmHg; p < 0.001) or a diet rich in fruits and vegetables with a reduced amount of snacks and sweets (−2.7/−1.9 mmHg; p ≤ 0.002). All 3 diets had a sodium content of 3 g per day. A subsequent study (DASH-Sodium) that explored the DASH diet or a control diet in combination with varying levels of sodium intake (high, intermediate, and low) found that the DASH diet significantly reduced SBP during the high, intermediate, and low sodium intake phases of both diets (high: −5.9 mmHg; p < 0.001; intermediate: −5.0 mmHg; p < 0.001; low: −2.2 mmHg; p < 0.05) [ 64 ]. The DASH diet also significantly reduced DBP versus the control diet during the high (−2.9 mmHg; p < 0.001) and intermediate (−2.5 mmHg; p < 0.01) sodium intake phases but not during the low intake phase (−1.0 mmHg). Although reducing sodium intake also significantly reduced blood pressure in the control diet group ( p < 0.05), the low sodium phase of the DASH diet elicited significant decreases in SBP/DBP of −8.9/−4.5 mmHg ( p < 0.001 for each) compared with high sodium intake phase of the control diet.

Subsequent controlled trials, as a whole, support the results of the DASH and DASH-Sodium studies in terms of blood pressure reduction. Moreover, these studies expanded the positive impacts of the DASH diet to include improvements in other cardiovascular risk factors or comorbidities (e.g., low-density lipoprotein cholesterol [LDL-C], total cholesterol, overweight/obesity, and insulin sensitivity) [ 65 , 66 , 67 , 68 ] and reductions in adverse outcomes such as development of cardiovascular disease, coronary heart disease, stroke, heart failure, metabolic syndrome, and diabetes (including improved pregnancy outcomes in women with gestational diabetes) [ 68 , 69 , 70 , 71 , 72 ]. Meta-analyses of studies using the DASH diet have demonstrated that LDL-C is significantly reduced by −0.1 mmol/L ( p = 0.03) [ 65 , 68 ], total cholesterol by −0.2 mmol/L ( p < 0.001) [ 65 , 68 ], body weight by −1.42 kg ( p < 0.001) [ 66 , 68 ], and fasting insulin by −0.15 μU/mL ( p < 0.001) [ 65 , 66 , 67 , 68 ]. With the DASH diet, the risk of cardiovascular disease is reduced by 20%, stroke by 19%, and heart failure by 29% ( p < 0.001 for each) [ 69 , 71 ]. The overall risk of diabetes is reduced by 18% [ 68 ], and children and adolescents with higher DASH scores (i.e., those whose diets included the highest intakes of fruits, vegetables, nuts, legumes, low-fat dairy, and whole grains) were at 64% lower risk of developing metabolic syndrome than those with the lowest DASH scores ( p = 0.023) [ 71 ]. Furthermore, rates of cesarean section decreased by 47% [ 72 ], incidence of macrosomia (birth weight > 4000 g) decreased from 39% to 4% ( p = 0.002) [ 70 ], and significantly fewer women experienced gestational diabetes that required insulin therapy on the DASH diet (23%) compared with the control diet (73%; p < 0.0001) [ 70 ].

The dietary pattern derived from the DASH study emphasizes the consumption of an array of vegetables (including colorful varieties, legumes, and starchy vegetables), fruits, fat-free or low-fat dairy products, whole grains, and various protein sources (e.g., seafood, lean meats, eggs, legumes, nuts, seeds, and soya) ( Table 1 ) [ 49 ]. Limited consumption of added sugars (< 10% of calories per day), saturated fats (< 10% of calories per day), sodium (< 2300 mg/day), and alcohol (≤ 1 drink per day for women and ≤ 2 drinks per day for men) is suggested. In addition, further reductions in blood pressure may be achievable by further reducing sodium intake, although practical challenges may limit the ability to achieve sodium intake of 1200 mg or less per day [ 49 ].

3.3. Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND)

The MIND diet combines elements of the Mediterranean and DASH diets with the goal of sustaining cognitive health throughout older age [ 9 ]. Both the Mediterranean and DASH diets have been individually linked to positive cognitive outcomes, including the prevention of cognitive decline or impairment and better cognitive performance [ 73 , 74 , 75 ]. Two high-quality cohort studies have reported associations between adherence to the MIND diet and a 53% lower risk for developing Alzheimer’s disease ( p = 0.002 for linear trend) [ 50 ] and slower declines in cognitive functioning, both overall and within specific cognitive domains (e.g., episodic, semantic, and working memory and perceptual speed and organization), such that the highest adherence rates to the MIND diet were associated with cognitive function equivalent to being 7.5 years younger [ 50 , 76 ]. Interestingly, even modest adherence to the MIND diet was associated with a 35% risk reduction for Alzheimer’s disease versus the lowest adherence group ( p = 0.002 for linear trend), whereas high adherence was needed to demonstrate 54% and 39% risk reductions with the Mediterranean and DASH diets, respectively; high adherence to the Mediterranean and DASH diet showed a statistically significant benefit [ 50 ].

The MIND diet focuses on increasing the intake of fresh fruits and vegetables and emphasizes brain-healthy foods such as green leafy vegetables, nuts, berries, beans, whole grains, fish, poultry, olive oil, and wine in moderation ( Table 1 ) [ 9 , 50 ]. Additionally, foods that are thought to be unhealthy for the brain, such as red meats, butter/margarine, cheese, pastries, sweets, and fried or fast food, are limited [ 9 ]. The specificity regarding the types of foods on the healthy and unhealthy lists differentiates MIND from the Mediterranean or DASH diets [ 50 ].

3.4. Nordic Diet

Iterations of a Nordic diet (e.g., the healthy Nordic diet, New Nordic Diet) arose from the desire to translate the Mediterranean, DASH, and other health-promoting diets into a regionally tailored dietary pattern that uses traditional, local Nordic foods and would be attractive to the public, sustainable, and eco-friendly [ 77 , 78 ]. Overarching tenets of the New Nordic Diet are to consume more (1) calories from plant sources and fewer from animal sources, (2) foods from seas and lakes, and (3) foods from the wild countryside [ 78 , 79 ]. A generalized Nordic dietary pattern would include green leafy vegetables, other vegetables, fruits, fish and seafood, potatoes, berries, whole grains (e.g., wheat, rye, oats, barley), nuts, low-fat dairy products, rapeseed, sunflower, and/or soya oils and limited intake of fresh red meat and sugar [ 78 , 80 ]. Specific dietary recommendations based on the NORDIET clinical trial are presented in Table 1 [ 51 ].

The randomized, controlled NORDIET study compared a healthy Nordic diet with a control diet (the participant’s usual Western diet) [ 77 ]. Over 6 weeks, the Nordic diet improved the lipid profile (including a 0.98 mmol/L reduction in total cholesterol [ p < 0.0001] and a 0.83 mmol/L reduction in LDL-C [ p < 0.001]), lowered SBP by 6.6 mmHg ( p = 0.008), and improved insulin sensitivity (homeostatic model assessment-insulin resistance decreased 0.11; p = 0.01) compared with the control diet. Those on the Nordic diet also experienced a 3.0 kg decrease in body weight ( p < 0.001) despite food being available ad libitum.

Results from subsequent studies conducted using Nordic diet variations are consistent with those from studies with the NORDIET study, demonstrating improvements relative to the control diet in blood lipid profile (LDL-C/HDL-C ratio, −0.15; p = 0.046) [ 81 ], inflammation (IL-1 receptor antagonist, −84 ng/L; p < 0.001) [ 81 ], blood pressure (DBP, −4.4 mmHg ( p = 0.001), and mean arterial pressure (−4.2 mmHg; p = 0.006) among patients with metabolic syndrome [ 82 ] and weight loss (−3.22 kg; p < 0.001) [ 83 ] and blood pressure reduction (SBP/DBP, −5.13/−3.24 mmHg; p < 0.05) in individuals with obesity [ 83 ]. Compared with baseline values, one study demonstrated blood pressure reductions of −6.9 mmHg (SBP) and −3.2 mmHg (DBP; p < 0.01) [ 83 , 84 ]. Additionally, a study conducted in children reported an improvement in omega-3 fatty acid status with the Nordic diet that was associated with improvements in school performance ( p < 0.05) [ 85 ]. A systematic review parsing the individual components of the Nordic diet found that evidence supported the protective effects of eating whole grains on type 2 diabetes and cardiovascular disease risk, but that there was insufficient evidence for other foods in the Nordic diet [ 86 ].

3.5. Traditional Asian Diets

Although there is substantial evidence supporting the Mediterranean and other European-based diets, traditional regional dietary patterns from other parts of the world that follow similar principles have less–well-established links to positive health outcomes. A full description of the breadth of regional diets and the associated evidence bases is beyond the scope of this publication, but we consider some Asian-based diets to be particularly relevant to this discussion.

The traditional Korean diet is composed of rice and other whole grains, fermented food, indigenous land and sea vegetables, proteins primarily from legumes and fish as opposed to red meat, medicinal herbs (e.g., garlic, green onions, ginger), and sesame and perilla oils [ 87 ]. Meals typically consist of multiple small-portion dishes are often derived from seasonal food sources and are home-cooked. Unlike the Western diet, the traditional Korean diet does not include many fried foods [ 87 ]. Epidemiologic data suggest a reduced risk of metabolic syndrome (odds ratio [OR]: 0.77; 95% CI: 0.60–0.99), obesity (OR: 0.72; 95% CI: 0.55–0.95), hypertension (OR: 0.74; 95% CI: 0.57–0.98), and hypertriglyceridemia (OR: 0.76; 95% CI: 0.59–0.99) among individuals who follow traditional Korean dietary patterns [ 88 ]. These findings are consistent with a controlled clinical trial that explored the effects of a traditional Korean diet compared with a control diet (“eat as usual”) on cardiovascular risk factors in patients with diabetes and hypertension. In that study, adherence to a traditional Korean diet favorably influenced body composition (body weight, −2.3 kg; body mass index [BMI], −0.83 kg/m 2 ; body fat, −2.2%; p < 0.01), heart rate (−7.1 bpm; p = 0.002), and glycemic control (HbA1c, −0.72%; p = 0.003) [ 89 ].

The traditional Chinese diet features rice or noodles, soups, vegetables, steamed breads or dumplings, fruits and vegetables, soy, seafood, and meat [ 90 , 91 ]. Although higher in carbohydrates and lower in fat compared with a Western diet, the traditional Chinese diet does not appear to promote weight gain in healthy, normal-weight Chinese, suggesting that carbohydrate restriction may not be a universally applicable intervention to combat obesity and cardiometabolic risk [ 92 ]. One 6-week controlled trial demonstrated that 52% of non-Chinese individuals with overweight or obesity who adhered to a traditional Chinese diet had a reduction in BMI while preserving lean body mass compared with 28% of those who followed a Western diet at the 1-year follow-up assessment [ 93 ]. In another trial, BMI decreased by 0.37 kg/m 2 and lean mass by 0.21 kg among subjects who adhered to a traditional Chinese diet for 6 weeks, whereas those who followed a Western diet had 0.26 kg/m 2 and 0.49 kg reductions in BMI and lean body mass, respectively [ 94 ]. Notably, both of these studies restricted caloric intake to 1,200 Kcal for the test and control diet groups.

Similar to the Korean diet, the traditional Japanese diet (known as Washoku) is characterized by small portions of multiple components, primarily including rice, fish (often eaten raw), soups, and pickles [ 95 ]. Fermented soybean paste (dashi) serves as the base of many of the soups that are central to the traditional Japanese diet; other ingredients include seaweed, fruits and vegetables, and mushrooms. The use of chopsticks, alternating between dishes of small portion size throughout a meal, and the base flavor of Japanese food (umami) enhance satiety and help to prevent overeating. Adherence to a traditional Japanese dietary pattern has been associated with favorable effects on blood pressure among apparently healthy Japanese adults [ 96 ]. This is consistent with data from the 2012 Japan National Health and Nutrition Survey demonstrating that adherence to a traditional Japanese diet compared with a Western diet or a meat- and fat-based dietary pattern was associated with a lower prevalence of hypertension in men [ 97 ]. However, in the same study, a traditional Japanese diet was associated with higher DBP in women, as well as higher waist circumference and BMI in men. Further study is needed to elucidate the health impacts of traditional Japanese and other Asian dietary patterns.

4. Additional Factors

While the evidence reviewed here suggests that the described dietary patterns positively influence measures of health and disease risk and outcome because they encourage the intake of foods that individually have beneficial effects and the avoidance of unhealthy options, additional factors combine to create a lifestyle that promotes health. For example, healthy diets include adequate hydration, typically in the form of water or tea/herbal infusions [ 7 , 49 , 51 , 52 ]. In addition to the dietary components, a healthy lifestyle is one that incorporates regular exercise, socialization, and adequate sleep [ 7 , 52 ], and minimizes elements that have a negative effect on health such as tobacco use, excessive alcohol consumption, physical inactivity, large amounts of screen time, and stress.

The importance of non-dietary factors is reflected in their inclusion in modern food pyramids. Built on a base of positive lifestyle factors, the lower tiers indicate daily consumption of adequate hydration and nutrient-rich, plant-based foods, with animal-derived products (meat, fish, and dairy) and sweets comprising higher tiers of the pyramid (i.e., less frequently or infrequently consumed items).

Whereas the goal may be to achieve nutrient requirements through food and water intake alone, there are situations in which food-derived nutrient intake might be inadequate due to increased need, selective eating, or food insecurity/limited access to more nutritious foods [ 98 , 99 , 100 ]. Therefore, for some individuals, dietary supplements may be required, particularly at certain life phases. For example, later in life, the recommended intake of calcium increases to sustain bone mineral density [ 101 ]; hence, supplementation with calcium may be necessary to meet recommended intake levels in older adults. Before initiating supplementation, dietary intake levels should be considered to avoid exceeding the upper tolerability limits and causing adverse events.

There are a number of other traditional regional diets that likely have similar benefits to those that we describe here. However, we made the decision to narrow our focus to those diets with evidence from randomized, controlled trials demonstrating their health benefits. For example, the African Heritage Diet focuses on traditional ingredients that may be beneficial to African American populations who experience disproportionately higher risks for chronic diseases related to their diets [ 102 ]. Future research is warranted to evaluate the impact of the African Heritage Diet and other regional dietary patterns on health.

5. Conclusions

Healthy diets, arising either by tradition or design, share many common features and generally align with the WHO Global Action Plan for the Prevention and Control of Noncommunicable Diseases. In comparison with a Western diet, these healthier alternatives are higher in plant-based foods, including fresh fruits and vegetables, whole grains, legumes, seeds, and nuts and lower in animal-based foods, particularly fatty and processed meats. Evidence from epidemiologic studies and clinical trials indicates that these types of dietary patterns reduce risks of NCDs ranging from cardiovascular disease to cancer. Further endeavors are needed to integrate these healthy dietary and lifestyle choices into daily living in communities throughout the world and to make healthy eating accessible, achievable, and sustainable.

Acknowledgments

Medical writing support was provided by Crystal Murcia, PhD, and Dennis Stancavish, MA, of Peloton Advantage, LLC, an OPEN Health company, and was funded by Pfizer Consumer Healthcare. On 1 August 2019, Pfizer Consumer Healthcare became part of GSK Consumer Healthcare.

Author Contributions

H.C. and P.C.C. contributed to the conception of the work; the acquisition, analysis, and interpretation of data; drafting; and revision of the work. Both have approved the final version for submission and agree to be personally accountable for their contributions and for ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated, resolved, and documented in the literature. All authors have read and agreed to the published version of the manuscript.

Medical writing support was funded by Pfizer Consumer Healthcare; this research received no other external funding. The APC was funded by Pfizer Consumer Healthcare. On 1 August 2019, Pfizer Consumer Healthcare became part of GSK Consumer Healthcare.

Conflicts of Interest

Hellas Cena received travel reimbursement from Pfizer Consumer Healthcare to attend a discussion meeting prior to drafting the manuscript and acts as a consultant to companies that manufacture or market dietary supplements, including Pfizer Consumer Healthcare. Philip C. Calder received travel reimbursement from Pfizer Consumer Healthcare to attend a discussion meeting prior to drafting the manuscript. Pfizer Consumer Healthcare funded this project, but the company had no role in the design, execution, interpretation, or writing of the paper.

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What Is a Case Study?

Weighing the pros and cons of this method of research

Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Cara Lustik is a fact-checker and copywriter.

Verywell / Colleen Tighe

• Pros and Cons

What Types of Case Studies Are Out There?

Where do you find data for a case study, how do i write a psychology case study.

A case study is an in-depth study of one person, group, or event. In a case study, nearly every aspect of the subject's life and history is analyzed to seek patterns and causes of behavior. Case studies can be used in many different fields, including psychology, medicine, education, anthropology, political science, and social work.

The point of a case study is to learn as much as possible about an individual or group so that the information can be generalized to many others. Unfortunately, case studies tend to be highly subjective, and it is sometimes difficult to generalize results to a larger population.

While case studies focus on a single individual or group, they follow a format similar to other types of psychology writing. If you are writing a case study, we got you—here are some rules of APA format to reference.  

At a Glance

A case study, or an in-depth study of a person, group, or event, can be a useful research tool when used wisely. In many cases, case studies are best used in situations where it would be difficult or impossible for you to conduct an experiment. They are helpful for looking at unique situations and allow researchers to gather a lot of˜ information about a specific individual or group of people. However, it's important to be cautious of any bias we draw from them as they are highly subjective.

What Are the Benefits and Limitations of Case Studies?

A case study can have its strengths and weaknesses. Researchers must consider these pros and cons before deciding if this type of study is appropriate for their needs.

One of the greatest advantages of a case study is that it allows researchers to investigate things that are often difficult or impossible to replicate in a lab. Some other benefits of a case study:

• Allows researchers to capture information on the 'how,' 'what,' and 'why,' of something that's implemented
• Gives researchers the chance to collect information on why one strategy might be chosen over another
• Permits researchers to develop hypotheses that can be explored in experimental research

On the other hand, a case study can have some drawbacks:

• It cannot necessarily be generalized to the larger population
• Cannot demonstrate cause and effect
• It may not be scientifically rigorous
• It can lead to bias

Researchers may choose to perform a case study if they want to explore a unique or recently discovered phenomenon. Through their insights, researchers develop additional ideas and study questions that might be explored in future studies.

It's important to remember that the insights from case studies cannot be used to determine cause-and-effect relationships between variables. However, case studies may be used to develop hypotheses that can then be addressed in experimental research.

Case Study Examples

There have been a number of notable case studies in the history of psychology. Much of  Freud's work and theories were developed through individual case studies. Some great examples of case studies in psychology include:

• Anna O : Anna O. was a pseudonym of a woman named Bertha Pappenheim, a patient of a physician named Josef Breuer. While she was never a patient of Freud's, Freud and Breuer discussed her case extensively. The woman was experiencing symptoms of a condition that was then known as hysteria and found that talking about her problems helped relieve her symptoms. Her case played an important part in the development of talk therapy as an approach to mental health treatment.
• Phineas Gage : Phineas Gage was a railroad employee who experienced a terrible accident in which an explosion sent a metal rod through his skull, damaging important portions of his brain. Gage recovered from his accident but was left with serious changes in both personality and behavior.
• Genie : Genie was a young girl subjected to horrific abuse and isolation. The case study of Genie allowed researchers to study whether language learning was possible, even after missing critical periods for language development. Her case also served as an example of how scientific research may interfere with treatment and lead to further abuse of vulnerable individuals.

Such cases demonstrate how case research can be used to study things that researchers could not replicate in experimental settings. In Genie's case, her horrific abuse denied her the opportunity to learn a language at critical points in her development.

This is clearly not something researchers could ethically replicate, but conducting a case study on Genie allowed researchers to study phenomena that are otherwise impossible to reproduce.

There are a few different types of case studies that psychologists and other researchers might use:

• Collective case studies : These involve studying a group of individuals. Researchers might study a group of people in a certain setting or look at an entire community. For example, psychologists might explore how access to resources in a community has affected the collective mental well-being of those who live there.
• Descriptive case studies : These involve starting with a descriptive theory. The subjects are then observed, and the information gathered is compared to the pre-existing theory.
• Explanatory case studies : These   are often used to do causal investigations. In other words, researchers are interested in looking at factors that may have caused certain things to occur.
• Exploratory case studies : These are sometimes used as a prelude to further, more in-depth research. This allows researchers to gather more information before developing their research questions and hypotheses .
• Instrumental case studies : These occur when the individual or group allows researchers to understand more than what is initially obvious to observers.
• Intrinsic case studies : This type of case study is when the researcher has a personal interest in the case. Jean Piaget's observations of his own children are good examples of how an intrinsic case study can contribute to the development of a psychological theory.

The three main case study types often used are intrinsic, instrumental, and collective. Intrinsic case studies are useful for learning about unique cases. Instrumental case studies help look at an individual to learn more about a broader issue. A collective case study can be useful for looking at several cases simultaneously.

The type of case study that psychology researchers use depends on the unique characteristics of the situation and the case itself.

There are a number of different sources and methods that researchers can use to gather information about an individual or group. Six major sources that have been identified by researchers are:

• Archival records : Census records, survey records, and name lists are examples of archival records.
• Direct observation : This strategy involves observing the subject, often in a natural setting . While an individual observer is sometimes used, it is more common to utilize a group of observers.
• Documents : Letters, newspaper articles, administrative records, etc., are the types of documents often used as sources.
• Interviews : Interviews are one of the most important methods for gathering information in case studies. An interview can involve structured survey questions or more open-ended questions.
• Participant observation : When the researcher serves as a participant in events and observes the actions and outcomes, it is called participant observation.
• Physical artifacts : Tools, objects, instruments, and other artifacts are often observed during a direct observation of the subject.

If you have been directed to write a case study for a psychology course, be sure to check with your instructor for any specific guidelines you need to follow. If you are writing your case study for a professional publication, check with the publisher for their specific guidelines for submitting a case study.

Here is a general outline of what should be included in a case study.

Section 1: A Case History

This section will have the following structure and content:

Background information : The first section of your paper will present your client's background. Include factors such as age, gender, work, health status, family mental health history, family and social relationships, drug and alcohol history, life difficulties, goals, and coping skills and weaknesses.

Description of the presenting problem : In the next section of your case study, you will describe the problem or symptoms that the client presented with.

Describe any physical, emotional, or sensory symptoms reported by the client. Thoughts, feelings, and perceptions related to the symptoms should also be noted. Any screening or diagnostic assessments that are used should also be described in detail and all scores reported.

Your diagnosis : Provide your diagnosis and give the appropriate Diagnostic and Statistical Manual code. Explain how you reached your diagnosis, how the client's symptoms fit the diagnostic criteria for the disorder(s), or any possible difficulties in reaching a diagnosis.

Section 2: Treatment Plan

This portion of the paper will address the chosen treatment for the condition. This might also include the theoretical basis for the chosen treatment or any other evidence that might exist to support why this approach was chosen.

• Cognitive behavioral approach : Explain how a cognitive behavioral therapist would approach treatment. Offer background information on cognitive behavioral therapy and describe the treatment sessions, client response, and outcome of this type of treatment. Make note of any difficulties or successes encountered by your client during treatment.
• Humanistic approach : Describe a humanistic approach that could be used to treat your client, such as client-centered therapy . Provide information on the type of treatment you chose, the client's reaction to the treatment, and the end result of this approach. Explain why the treatment was successful or unsuccessful.
• Psychoanalytic approach : Describe how a psychoanalytic therapist would view the client's problem. Provide some background on the psychoanalytic approach and cite relevant references. Explain how psychoanalytic therapy would be used to treat the client, how the client would respond to therapy, and the effectiveness of this treatment approach.
• Pharmacological approach : If treatment primarily involves the use of medications, explain which medications were used and why. Provide background on the effectiveness of these medications and how monotherapy may compare with an approach that combines medications with therapy or other treatments.

This section of a case study should also include information about the treatment goals, process, and outcomes.

When you are writing a case study, you should also include a section where you discuss the case study itself, including the strengths and limitiations of the study. You should note how the findings of your case study might support previous research. 

In your discussion section, you should also describe some of the implications of your case study. What ideas or findings might require further exploration? How might researchers go about exploring some of these questions in additional studies?

Need More Tips?

Here are a few additional pointers to keep in mind when formatting your case study:

• Never refer to the subject of your case study as "the client." Instead, use their name or a pseudonym.
• Read examples of case studies to gain an idea about the style and format.
• Remember to use APA format when citing references .

Crowe S, Cresswell K, Robertson A, Huby G, Avery A, Sheikh A. The case study approach .  BMC Med Res Methodol . 2011;11:100.

Crowe S, Cresswell K, Robertson A, Huby G, Avery A, Sheikh A. The case study approach . BMC Med Res Methodol . 2011 Jun 27;11:100. doi:10.1186/1471-2288-11-100

Gagnon, Yves-Chantal.  The Case Study as Research Method: A Practical Handbook . Canada, Chicago Review Press Incorporated DBA Independent Pub Group, 2010.

Yin, Robert K. Case Study Research and Applications: Design and Methods . United States, SAGE Publications, 2017.

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

Methods in Nutrition Research

• First Online: 11 May 2023

Cite this chapter

• David R. Jacobs Jr. 7 &
• Norman J. Temple 8  

Part of the book series: Nutrition and Health ((NH))

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Many different research designs are available for investigating nutrition-related questions. Each one has strengths and weaknesses. Much nutrition-related research is carried out using epidemiological study designs. Many epidemiological studies use observational designs; these include prospective cohort studies, case-control studies, cross-sectional studies, population studies, and historical studies. Results from randomized controlled trials (RCTs) are internally valid and are usually more reliable for causal inference than those from observational epidemiological studies. However, many kinds of nutritional studies do not fit well into the RCT framework. A recent development is the use of systematic reviews and meta-analyses. First, the literature is reviewed according to strict criteria. Findings from the studies are then analyzed in order to make pooled risk estimates. These gain power by increasing sample size; however, variables and concepts will vary across studies. This strategy can be valuable in evaluating consistency and in considering the possibility of residual confounding when only observational studies are available. Experiments on animals are often used for nutrition-related research. However, animal models have many differences from the human situation. Much mechanistic research is carried out where researchers study the details of body functioning such as physiology and biochemistry. This can illuminate detailed cellular and molecular relationships, but integrating such findings with the biology of intact humans is problematic. There is evidence of conflict of interest in studies that potentially affect profit of the research funder, most typically in industry funding. This indicates a need for particular care in interpreting such studies. A sufficient pool of research funds, independent of the food industry, is highly desirable to support needed research. Research studies involving human subjects require approval from an ethics committee.

• Epidemiological studies
• Cohort studies
• Case-control studies
• Cross-sectional studies
• Population studies
• Historical studies
• Randomized controlled trials
• Systematic review
• Meta-analysis
• Conflict of interest
• Ethical approval

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Jacobs, D.R., Temple, N.J. (2023). Methods in Nutrition Research. In: Temple, N.J., Wilson, T., Jacobs, Jr., D.R., Bray, G.A. (eds) Nutritional Health. Nutrition and Health. Humana, Cham. https://doi.org/10.1007/978-3-031-24663-0_1

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Published : 11 May 2023

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