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• Salt: Research

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• Salt: Resources

EPA Research on Freshwater Salinization Syndrome

Drinking water and groundwater, salt in the environment, source reduction.

• Effects of Road Salts on Groundwater and Surface Water Dynamics of Sodium and Chloride in an Urban Restored Stream
• Sensors Track ‘Chemical Cocktails’ in Streams Impacted by Road Salts in the Chesapeake Bay Watershed
• Five State Factors Control Progressive Stages of Freshwater Salinization Syndrome
• Freshwater Salinization Syndrome Alters Retention and Release of ‘Chemical Cocktails’ Along Flowpaths: from Stormwater Management to Urban Streams
• Human-Accelerated Weathering Increases Salinization, Major Ions, and Alkalinization in Fresh Water Across Land Use
• Making ‘Chemical Cocktails’ – Evolution of Urban Geochemical Processes Across the Periodic Table of Elements
• Watershed ‘Chemical Cocktails’: Forming Novel Elemental Combinations in Anthropocene Fresh Waters
• Elevated Blood Lead Levels in Children Associated With the Flint Drinking Water Crisis: A Spatial Analysis of Risk and Public Health Response
• Health Cost of Salinity Contamination in Drinking Water: Evidence from Bangladesh
• Chloride-to-Sulfate Mass Ratio and Lead Leaching to Water
• Assessing the Lead Solubility Potential of Untreated Groundwater of the United States
• Review of Implications of Road Salt Use on Groundwater Quality—Corrosivity and Mobilization of Heavy Metals and Radionuclides
• Mobilization of Radium and Radon by Deicing Salt Contamination of Groundwater
• Impact of Road Salt on Drinking Water Quality and Infrastructure Corrosion in Private Wells
• Increasing Chloride in Rivers of the Conterminous U.S. and Linkages to Potential Corrosivity and Lead Action Level Exceedances in Drinking Water
• Potential Corrosivity of Untreated Groundwater in the United States
• Groundwater Chloride Concentrations in Domestic Wells and Proximity to Roadways in Vermont, 2011–2018
• Freshwater Salinization Syndrome on a Continental Scale
• A Review of the Combined Threats of Road Salts and Heavy Metals to Freshwater Systems
• Saltwater Intrusion Affects Nutrient Concentrations in Soil Porewater and Surface Waters of Coastal Habitats
• Salinity Increases the Mobility of Cd, Cu, Mn, and Pb in the Sediments of Yangtze Estuary: Relative Role of Sediments’ Properties and Metal Speciation
• Chloride Contributions from Water Softeners and Other Domestic, Commercial, Industrial, and Agricultural Sources to Minnesota Waters
• Salinity Increases Mobility of Heavy Metals in Soils
• Mobilisation of Heavy Metals by Deicing Salts in a Roadside Environment
• Freshwater Salinization Syndrome: From Emerging Global Problem to Managing Risks
• Salinization Triggers a Trophic Cascade in Experimental Freshwater Communities with Varying Food-Chain Length
• Methods for Evaluating Potential Sources of Chloride in Surface Waters and Groundwaters of the Conterminous United States
• Proteolysis During Cheese Manufacture and Ripening
• An Economic Assessment of the Social Costs of Highway Salting and the Efficiency of Substituting a New Deicing Material
• Review Removal of Chloride from Water and Wastewater
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Salt and Sodium

Salt, also known as sodium chloride, is about 40% sodium and 60% chloride . It flavors food and is used as a binder and stabilizer. It is also a food preservative, as bacteria can’t thrive in the presence of a high amount of salt. The human body requires a small amount of sodium to conduct nerve impulses, contract and relax muscles, and maintain the proper balance of water and minerals. It is estimated that we need about 500 mg of sodium daily for these vital functions. But too much sodium in the diet can lead to high blood pressure, heart disease, and stroke. It can also cause calcium losses, some of which may be pulled from bone. Most Americans consume at least 1.5 teaspoons of salt per day, or about 3400 mg of sodium, which contains far more than our bodies need.

Recommended Amounts

The U.S. Dietary Reference Intakes state that there is not enough evidence to establish a Recommended Dietary Allowance or a toxic level for sodium (aside from chronic disease risk). Because of this, a Tolerable Upper intake Level (UL) has not been established; a UL is the maximum daily intake unlikely to cause harmful effects on health.  

Guidelines for Adequate Intakes (AI) of sodium were established based on the lowest levels of sodium intake used in randomized controlled trials that did not show a deficiency but that also allowed for an adequate intake of nutritious foods naturally containing sodium. For men and women 14 years of age and older and pregnant women, the AI is 1,500 milligrams a day.

A Chronic Disease Risk Reduction (CDRR) Intake has also been established, based on the evidence of benefit of a reduced sodium intake on the risk of cardiovascular disease and high blood pressure. Reducing sodium intakes below the CDRR is expected to lower the risk of chronic disease in the general healthy population. The CDRR lists 2,300 milligrams a day as the maximum amount to consume for chronic disease reduction for men and women 14 years of age and older and pregnant women. Most people in the U.S. consume more sodium than the AI or CDRR guidelines. [1]

Types of Salt

Finely ground salts are dense, so they tend to contain more sodium than coarser salts. Note that sodium content can vary widely among brands, so check the Nutrition Facts label for exact amounts.

† The inclusion of brand-names on this list is for reference only and does not constitute an endorsement. The Nutrition Source does not endorse specific brands. 

Sodium and Health

In most people, the kidneys have trouble keeping up with excess sodium in the blood. As sodium accumulates, the body holds onto water to dilute the sodium. This increases both the amount of fluid surrounding cells and the volume of blood in the bloodstream. Increased blood volume means more work for the heart and more pressure on blood vessels. Over time, the extra work and pressure can stiffen blood vessels, leading to high blood pressure, heart attack, and stroke. It can also lead to heart failure. There is some evidence that too much salt can damage the heart, aorta, and kidneys without increasing blood pressure, and that it may be bad for bones, too. Learn more about the health risks and disease related to salt and sodium:

After conducting a review on sodium research, the Institute of Medicine concluded that reducing sodium intake lowers blood pressure, but evidence of a decreased risk of cardiovascular diseases (CVD) is inconclusive. [2] It is clear, however, that high blood pressure is a leading cause of CVD. It accounts for two-thirds of all strokes and half of heart disease. [3] In China, high blood pressure is the leading cause of preventable death, responsible for more than one million deaths a year. [4]

There may be a genetic component to salt intake, as people respond differently to lower sodium intakes. [2] Those who are “salt-sensitive” experience the greatest blood pressure reductions after following a reduced sodium diet. Those who are “salt-resistant” do not experience these changes even with significant increases in sodium intake. Studies have found that women more than men, people older than 50 years, African-Americans, and those with a higher starting blood pressure respond the greatest to reduced sodium intake. [5,6] However, there is not enough evidence to make strong conclusions about specific groups who may be salt-resistant; the overall evidence supports a benefit of limiting sodium intake for everyone, even though the optimal target amount is not clear.

Observational and clinical research has found that higher sodium intakes are associated with cardiovascular diseases and related deaths. The following are key studies:

• The authors conducted a re-review and update on the Intersalt data. [8] They found: 1) a stronger association than their prior study with higher sodium intakes and higher blood pressure, and 2) a stronger association with higher sodium intakes and higher blood pressure in middle age participants as compared with younger adults.
• After an average of 10-15 years, the TOHP participants in the sodium-reduction groups were 25% less likely to have had a heart attack or stroke, to have needed a procedure to open or bypass a cholesterol-clogged coronary artery, or to have died of cardiovascular disease.
• The higher the ratio of potassium to sodium in a participant’s diet, the lower the chances were of developing cardiovascular trouble. This suggests that a strategy that includes both increasing potassium and lowering sodium may be the most effective way to fight high blood pressure.
• TOHP Follow-up Study : A continuation of the two previous TOHP trials in 2000 that looked specifically at CVD or deaths from CVD. [11] When participants with sodium intakes less than 2,300 mg daily were compared with those who had intakes of 3,600-4,800 mg, there was a 32% lower risk of developing CVD. There was also a continuing decrease in CVD-related events (stroke, heart attack) with decreasing sodium intakes as low as 1,500 mg daily.
• In the first study, 459 participants were randomly assigned to either 1) a standard American diet high in red meat and sugars, and low in fiber, 2) a similar diet that was richer in fruits and vegetables, or 3) the “ DASH diet ,” which emphasized fruits, vegetables and low-fat dairy foods, and limited red meat, saturated fats, and sweets. After eight weeks, the fruits and vegetables diet and DASH diet reduced systolic (the top number of a blood pressure reading) and diastolic (the bottom number of a blood pressure reading) blood pressure, with the DASH diet producing a stronger effect.
• The second study found that lowering sodium in either the DASH or standard American diet had an even stronger impact on reducing blood pressure. The DASH study contributed much of the scientific basis for the Dietary Guidelines for Americans 2010, which recommends reducing daily sodium to less than a teaspoon.
• A meta-analysis of clinical trials found that a moderate sodium reduction to about 4,000 mg a day for at least one month caused significant reductions in blood pressure in individuals with both normal and high blood pressure. Further analysis showed that blood pressure was reduced in both men and women and white and black races, suggesting a benefit for the total population. [6]

Assessing people’s sodium intakes can be tricky, and the most accurate method known is to measure 24-urine samples over several days. This is the method Harvard researchers used when pooling data from 10,709 generally healthy adults from six prospective cohorts including the Nurses Health Studies I and II, the Health Professionals Follow-up Study, the Prevention of Renal and Vascular End-Stage Disease study, and the Trials of Hypertension Prevention Follow-up studies. [22] They looked at both sodium and potassium intakes in relation to cardiovascular disease (CVD) risk (as noted by a heart attack, stroke, or procedure or surgery needed to repair heart damage), and measured two or more urine samples per participant. After controlling for CVD risk factors, they found that a higher sodium intake was associated with higher CVD risk. For every 1,000 mg increase of urinary sodium per day, there was an 18% increased risk of CVD. But for every 1,000 mg increase of potassium, there was an 18% lower risk of CVD. They also found that a higher sodium-to-potassium ratio was associated with higher CVD risk, that is, eating a higher proportion of salty foods to potassium-rich foods such as fruits, vegetables, legumes, and low-fat dairy.

Chronic kidney disease (CKD) shares risk factors with cardiovascular disease, with high blood pressure being a major risk factor for both. Salt sensitivity is reported to be more prevalent in patients with CKD due to a reduced ability to excrete sodium, which may lead to increased blood pressure. [14]

Although there is evidence that links high sodium intake with high blood pressure, there is not adequate evidence that a low sodium restriction protects against or causes better outcomes of CKD than a moderate sodium restriction. One systematic review of patients diagnosed with CKD found that high sodium intakes of greater than 4,600 mg a day were associated with progression of CKD, but low sodium intakes less than 2,300 mg a day had no significant effect when compared with moderate sodium intakes of 2,300-4,600 mg a day. [14]

Guidelines generally advise a moderate rather than low sodium restriction to prevent the development and progression of CKD. A daily sodium intake of less than 4,000 mg is recommended for overall management of CKD, and less than 3,000 mg daily for CKD with symptoms of fluid retention or proteinuria, a condition in which excess protein is excreted in the urine. [15]

The amount of calcium that your body loses via urination increases with the amount of salt you eat. If calcium is in short supply in the blood, it can leach out of bones. So a diet high in sodium could have an additional unwanted effect—the bone-thinning disease known as osteoporosis. [3] A study in post-menopausal women showed that the loss of hip bone density over two years was related to the 24-hour urinary sodium excretion at the start of the study, and that the connection with bone loss was as strong as that for calcium intake. [16] Other studies have shown that reducing salt intake causes a positive calcium balance, suggesting that reducing salt intake could slow the loss of calcium from bone that occurs with aging.

Research shows that a higher intake of salt, sodium, or salty foods is linked to an increase in stomach cancer. The World Cancer Research Fund and American Institute for Cancer Research concluded that salt, as well as salted and salty foods, are a “probable cause of stomach cancer.” [17]

Food Sources

Sodium isn’t generally a nutrient that you need to look for; it finds you. Almost any unprocessed food like fruits, vegetables, whole grains, nuts, meats, and dairy foods is low in sodium. Most of the salt in our diets comes from commercially prepared foods, not from salt added to cooking at home or even from salt added at the table before eating. [1,18]

According to The Centers for Disease Control and Prevention, the top 10 sources of sodium in our diets include: breads/rolls; pizza; sandwiches; cold cuts/cured meats; soups; burritos, tacos; savory snacks (chips, popcorn, pretzels, crackers); chicken; cheese; eggs, omelets.

Are “natural” salts healthier than table salt?

Kosher salt is a coarsely grained salt named for its use in traditional Kosher food preparation. Kosher salt does not typically contain iodine but may have an anti-caking agent.

Sea salt is produced by evaporating ocean or sea water. It is also composed mostly of sodium chloride, but sometimes contains small amounts of minerals like potassium, zinc, and iron depending on where it was harvested. Because it is not highly refined and ground like table salt, it may appear coarser and darker with an uneven color, indicating the remaining impurities and nutrients. Unfortunately, some of these impurities can contain metals found in the ocean, like lead. The coarseness and granule size will vary by brand.

Larger, coarser salt granules do not dissolve as easily or evenly in cooking, but offer a burst of flavor. They are best used sprinkled onto meats and vegetables before cooking or immediately after. They should not be used in baking recipes. Keep in mind that measurements of different salts are not always interchangeable in recipes. Generally, sea salt and table salt can be interchanged if the granule size is similar. However, table salt tends to have more concentrated, saltier flavor than kosher salt, so the substitution is one teaspoon of table salt for about 1.5 to 2 teaspoons of kosher salt depending on the brand.

Signs of Deficiency and Toxicity

A deficiency of sodium in the U.S. is rare because it is so commonly added to a wide variety of foods and occurs naturally in some foods. Hyponatremia is the term used to describe abnormally low amounts of sodium in the blood. This occurs mainly in older adults, particularly those living in long-term care facilities or hospitals who take medications or have health conditions that deplete the body of sodium, leading to hyponatremia. Excess vomiting, diarrhea, and sweating can also cause hyponatremia if salt is lost in these fluids that are expelled from the body. Sometimes too much fluid abnormally collecting in the body can lead to hyponatremia, which might stem from diseases such as heart failure or liver cirrhosis. In rare cases, simply drinking too much fluid can lead to hyponatremia if the kidneys can’t excrete the excess water. Symptoms of hyponatremia can include: nausea, vomiting, headaches, altered mental state/confusion, lethargy, seizures, coma.

Too much sodium in the blood is called hypernatremia . This acute condition can happen in older adults who are mentally and physically impaired who do not eat or drink enough, or who are sick with a high fever, vomiting, or infection that causes severe dehydration. Excessive sweating or diuretic medications that deplete the body of water are other causes. When sodium accumulates in the blood, water is transferred out of cells and into the blood to dilute it. This fluid shift and a build-up of fluid in the brain can cause seizures, coma, or even death. Extra fluid collecting in the lungs can cause difficulty breathing. Other symptoms of hypernatremia can include: nausea, vomiting, weakness, loss of appetite, intense thirst, confusion, kidney damage.

The interplay of sodium and potassium

A study in the Archives of Internal Medicine found that:

• People who ate high-sodium, low-potassium diets had a higher risk of dying from a heart attack or any cause. In this study, people with the highest sodium intakes had a 20% higher risk of death from any cause than people with the lowest sodium intakes. People with the highest potassium intakes had a 20% lower risk of dying than people with the lowest intakes. But what may be even more important for health is the relationship of sodium to potassium in the diet. People with the highest ratio of sodium to potassium in their diets had double the risk of dying of a heart attack than people with the lowest ratio, and they had a 50% higher risk of death from any cause. [21]
• People can make a key dietary change to help lower their risk: Eat more fresh vegetables and fruits, which are naturally high in potassium and low in sodium, but eat less bread, cheese, processed meat, and other processed foods that are high in sodium and low in potassium.

Take Action: How to Reduce Your Sodium Intake Public Health Concerns: Salt and Sodium Vitamins and Minerals

• Dietary Reference Intakes for Sodium and Potassium. Washington (DC): National Academies Press (US); 2019 Mar.
• Stallings VA, Harrison M, Oria M. Committee to Review the Dietary Reference Intakes for Sodium and Potassium; Food and Nutrition Board; Health and Medicine Division; National Academies of Sciences, Engineering, and Medicine.
• He FJ, MacGregor GA. A comprehensive review on salt and health and current experience of worldwide salt reduction programmes. Journal of human hypertension . 2009 Jun;23(6):363.
• He J, Gu D, Chen J, Wu X, Kelly TN, Huang JF, Chen JC, Chen CS, Bazzano LA, Reynolds K, Whelton PK. Premature deaths attributable to blood pressure in China: a prospective cohort study. The Lancet . 2009 Nov 21;374(9703):1765-72.
• Aburto NJ, Ziolkovska A, Hooper L, Elliott P, Cappuccio FP, Meerpohl JJ. Effect of lower sodium intake on health: systematic review and meta-analyses. BMJ . 2013 Apr 4;346:f1326.
• He FJ, Li J, MacGregor GA. Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials. BMJ . 2013 Apr 4;346:f1325.
• Intersalt Cooperation Research Group. Intersalt Cooperation Research Group Intersalt: an international study of electrolyte excretion and blood pressure. Results for 24-hour urinary sodium and potassium. BMJ . 1988;297:319-28.
• Elliott P, Stamler J, Nichols R, Dyer AR, Stamler R, Kesteloot H, Marmot M. Intersalt revisited: further analyses of 24 hour sodium excretion and blood pressure within and across populations. BMJ . 1996 May 18;312(7041):1249-53.
• Cook NR, Cutler JA, Obarzanek E, Buring JE, Rexrode KM, Kumanyika SK, Appel LJ, Whelton PK. Long term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention (TOHP). BMJ . 2007 Apr 26;334(7599):885.
• Cook NR, Obarzanek E, Cutler JA, Buring JE, Rexrode KM, Kumanyika SK, Appel LJ, Whelton PK. Joint effects of sodium and potassium intake on subsequent cardiovascular disease: the Trials of Hypertension Prevention follow-up study. Archives of internal medicine . 2009 Jan 12;169(1):32-40.
• Cook NR, Appel LJ, Whelton PK. Lower levels of sodium intake and reduced cardiovascular risk. Circulation . 2014 Mar 4;129(9):981-9. *Disclosures: Dr. Appel is an investigator on a grant from the McCormick Foundation.
• Appel LJ, Moore TJ, Obarzanek E, Vollmer WM, Svetkey LP, Sacks FM, Bray GA, Vogt TM, Cutler JA, Windhauser MM, Lin PH. A clinical trial of the effects of dietary patterns on blood pressure. New England Journal of Medicine . 1997 Apr 17;336(16):1117-24.
• Sacks FM, Svetkey LP, Vollmer WM, Appel LJ, Bray GA, Harsha D, Obarzanek E, Conlin PR, Miller ER, Simons-Morton DG, Karanja N. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. New England Journal of Medicine . 2001 Jan 4;344(1):3-10.
• Smyth A, O’donnell MJ, Yusuf S, Clase CM, Teo KK, Canavan M, Reddan DN, Mann JF. Sodium intake and renal outcomes: a systematic review. American journal of hypertension . 2014 Oct 1;27(10):1277-84.
• Kalantar-Zadeh K, Fouque D. Nutritional management of chronic kidney disease. New England Journal of Medicine . 2017 Nov 2;377(18):1765-76.
• Devine A, Criddle RA, Dick IM, Kerr DA, Prince RL. A longitudinal study of the effect of sodium and calcium intakes on regional bone density in postmenopausal women. The American journal of clinical nutrition . 1995 Oct 1;62(4):740-5.
• World Cancer Research Fund, American Institute for Cancer Research. Food, Nutrition, Physical Activity, and the Prevention of Cancer:  A Global Perspective. London; 2007.
• Centers for Disease Control and Prevention. Sodium and Food Sources. https://www.cdc.gov/salt/food.htm Accessed 3/18/2019
• Brown IJ, Tzoulaki I, Candeias V, Elliott P. Salt intakes around the world: implications for public health. International journal of epidemiology . 2009 Apr 7;38(3):791-813.
• Dietary Guidelines for Americans Scientific Advisory Committee. Report of the Dietary Guidelines Advisory Committee on the Dietary Guidelines for Americans, 2010, to the Secretary of Agriculture and the Secretary of Health and Human Services. 2010.
• Yang Q, Liu T, Kuklina EV, Flanders WD, Hong Y, Gillespie C, Chang MH, Gwinn M, Dowling N, Khoury MJ, Hu FB. Sodium and potassium intake and mortality among US adults: prospective data from the Third National Health and Nutrition Examination Survey. Archives of internal medicine . 2011 Jul 11;171(13):1183-91.
• Ma Y, He FJ, Sun Q, Yuan C, Kieneker LM, Curhan GC, MacGregor GA, Bakker SJ, Campbell NR, Wang M, Rimm EB. 24-Hour Urinary Sodium and Potassium Excretion and Cardiovascular Risk. New England Journal of Medicine . 2021 Nov 13.

Last reviewed March 2023

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How molten salt could be the lifeblood of tomorrow’s nuclear energy

June 19, 2023

By Addison Arave

Salt isn’t just for popcorn anymore. In fact, molten salt has caught the eye of the nuclear industry as an ideal working fluid for reactor cooling, energy transfer, fueling and fission product absorption. Many of the salts being considered are inexpensive, nontoxic, and easily transportable. In fact, table salt is one of the constituents many reactor developers are choosing to use.   

Heightened interest in molten salt reactors (MSRs) has led to increased investment in their research and development. Idaho National Laboratory has already dedicated efforts to establish comprehensive molten salt capabilities. In the coming years, these efforts will establish a molten salt characterization facility, irradiate fuel salt and, for the first time, start up an experimental “fast” reactor that runs on molten salt.  

“Molten salt research is essential for the future of nuclear energy, and INL is the ideal resource for industry projects in this area,” said Advanced Technology of Molten Salts Manager John Carter. “MSRs are an attractive option for future power generation, and we are prepared to make significant progress toward full-scale operations.”   

Why salt?  

Molten salt, as a coolant and nuclear fuel, offers numerous safety, efficiency and flexibility benefits.   

Interestingly, molten salt fuel comes with an inherent safety feature. If the salt overheats, it naturally expands and makes the fission reaction less effective, which shuts down the reactor. The MSR reactor core naturally changes its power level to match heat removal for electricity production, allowing it to appropriately meet consumer demand.  

Another benefit: fuel flexibility. Uranium, plutonium and thorium all form salts that can be used as fuel for MSRs. At reactor operating temperatures, the salt is liquid, which means new fuel can be introduced and in-use fuel can be cleaned, filtered and managed during operation. This eliminates the need for refueling outages.   

Molten salt fuel opens a whole new world of possibilities to reactor designers. The characteristically high temperatures in MSRs translate into efficient electrical power conversion, but the low-pressure feature eliminates the need for costly, thick-walled pipes and tanks.   

The use of fast neutrons has its own set of benefits as well.  

What are fast neutrons?  

A fast-spectrum nuclear reactor uses fast, high-energy neutrons to sustain the nuclear reaction. Fast neutrons are more effective than slow neutrons at consuming certain waste products. This greatly reduces the amount of long-lived waste that must be isolated from the environment.   

While fast-spectrum reactors can produce clean and reliable electricity for the grid, they can also provide thermal energy for industrial needs such as water desalination, aluminum and steel production, hydrogen production, and carbon capture. Today, those processes burn fossil fuels to generate high-temperature heat. Getting that heat from the power of fission instead would further reduce the globe’s dependence on carbon-based energy sources.   

With these benefits in mind, the prospect of adopting a fast-spectrum, salt-based MSR design is a high priority for the nuclear energy industry, the United States and international governments.   

What research is happening now?  

INL researchers and engineers are helping answer some outstanding questions about MSR technologies.   

For instance, as part of the Molten Salt Research Temperature Controlled Irradiation project, a Laboratory Directed Research and Development project at INL, researchers have designed the first fuel-bearing molten chloride salt irradiation experiment. This experiment places encapsulated fuel salt into an operating reactor to better understand how chloride fuel salt properties change during irradiation. The test is planned for later this year.  

Another project, the Molten Salt Thermophysical Examination Capability, is a state-of-the-art facility where researchers will use specialized equipment inside a shielded glovebox to handle and closely examine irradiated fuel salt. Researchers hope to learn how materials will behave under operating conditions by observing their density, heat capacity and viscosity. The team should complete this National Reactor Innovation Center project next year.   

INL is also part of a team developing the Molten Chloride Reactor Experiment (MCRE), a six-month sub-scale test that will demonstrate the first operational fast spectrum molten salt reactor in the world. In partnership with Southern Company and TerraPower, INL will synthesize and handle the fuel salt, load and operate the reactor, and perform all post-operation deactivation and disassembly work. The test-bed experiment, a public-private partnership under the Department of Energy Office of Nuclear Energy’s Advanced Reactor Demonstration Program, is expected to begin operation as soon as 2027 and will provide the data necessary to take the next step toward licensing a commercial Molten Chloride Fast Reactor.  

“It is incredible to see so much knowledge and talent come together for the MCRE Project” said Nick Smith, MCRE Project Director. “We are leveraging INL’s experience in fuel and reactor demonstrations, combining that with the innovative ideas and sense of urgency of our industry partners, and working through the engineering of a technology no one has ever built before. It is the most exciting thing I have ever been a part of.”  

INL is also leading research related to molten salt properties, risk mitigation and MSR condition optimization with the help of dedicated computational modeling efforts.   

Multiphysics computer modeling and simulations have been developed or customized specifically for MSRs using INL’s open-source Multiphysics Objected-Oriented Simulation Environment, or MOOSE, code. This application allows researchers to create precise digital models across multiple scales, materials and research areas. These high-fidelity simulations, informed by real-world experiments, help researchers and industry enhance MSR safety and performance by reliably predicting molten salt properties, thermodynamics and irradiation behaviors.  

“The research activities going on at INL will help advance the technical readiness level of advanced molten salt reactors,” said research scientist Toni Karlsson. “INL has technical staff members with a passion for molten salts and unique experimental capabilities for actinide and irradiated salts not found anywhere else in the world. Along with industry partners, we are bridging the gap from advanced reactor development to deployment.”    

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The salt research group.

UC Berkeley Nuclear Engineering Department

SALT Lab, led by nuclear engineering professor Raluca Scarlat, at UC Berkeley’s Etcheverry Hall in Berkeley, Calif. on Monday, Feb. 26, 2024. (Photo by Adam Lau/Berkeley Engineering)

SALT || Reactor S afety & Inorg A nic Chemistry of L ight Elements at High T emperature

We apply our research to fluoride-salt-cooled high-temperature reactors (FHRs) and Molten Salt Reactors (MSRs), high-temperature gas cooled reactors (HTGRs), and tritium-breeding blankets for fusion systems.  Our research includes safety analysis, licensing and design of nuclear reactors, and extends to engineering ethics.

Open positions and involvement with the group

• We are currently looking for 2 undergraduate students to work on electrochemistry research. Please fill out above application and reach out to Michael Borrello ( [email protected] )
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• Special Issue: Current evidence and perspectives for hypertension management in Asia
• Published: 10 April 2024

Effects of salt intake reduction by urinary sodium to potassium ratio self-monitoring method

• Masahiro Shimoyama 1 ,
• Shinya Kawamoto 1 ,
• Yuki Nakatani 2 ,
• Nobuyuki Banba 2 ,
• Yasuko Nagashima 2 ,
• Takashi Tomoe 1 ,
• Takushi Sugiyama 1 ,
• Asuka Ueno 1 ,
• Keijiro Kitahara 3 ,
• Atsuhiko Kawabe 1 ,
• Naoyuki Otani 3 ,
• Hiroyuki Sugimura 3 &
• Takanori Yasu 1  

Hypertension Research ( 2024 ) Cite this article

Metrics details

Effective and feasible educational methods are needed to control salt intake. We performed a single-center, non-randomized controlled study to investigate the effectiveness and feasibility of self-monitoring using a urinary sodium/potassium (Na/K) ratio-measuring device in patients with difficulty in reducing salt intake. This study included 160 patients with hypertension, chronic kidney disease, or heart disease who were followed up in the outpatient clinic of the Dokkyo Medical University Nikko Medical Center. Urinary Na/K ratio measuring Na/K ratio meter were loaned for 2–6 weeks to the treatment (T) group ( n  = 80) and not to the patients in the control (C) group ( n  = 80). In the T group, patients were instructed to measure the urinary Na/K ratio at least three times a day and maintain a Na/K ratio below 2.0. Salt reduction education and home blood pressure measurement guidance continued in both groups. The mean device loan period in the T group was 25.1 days, the mean number of measurements was 3.0 times/day, and the proportion of patients achieving three measurements per day was 48.8% (39/80). Self-monitoring using the urinary Na/K ratio meter successfully reduced salt intake by −1.9 g/day at the second visit ( p  < 0.001) in the T group. In contrast, no change was observed over time in the C group. Self-monitoring using the urinary Na/K ratio meter successfully reduced salt intake in patients with difficulty reducing salt intake.

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Acknowledgements

MS designed the research and wrote the initial draft of the manuscript together with TY; TY conceived of the study and participated in its design and coordination and helped draft the manuscript; SK and NO helped draft the manuscript ; YN, NB, TT, TS, AU, KK, AK, HS, and YN participated in data collection; MS performed statistical analysis; The authors express their gratitude to N. Yamakoshi, Y. Murakami, and K. Yoshizawa for their assistance with data entry and administrative support for this study. We would like to thank Editage ( www.editage.jp ) for English language editing.

This study was supported by Dokkyo Medical University, Project Research Grant (2015-09) to MS and YN, and Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan (No. 26350581) to TY.

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Department of Cardiovascular Medicine and Nephrology, Dokkyo Medical University Nikko Medical Center, 145-1 Moritomo, Nikko, Tochigi, 321 -1298, Japan

Masahiro Shimoyama, Shinya Kawamoto, Takashi Tomoe, Takushi Sugiyama, Asuka Ueno, Atsuhiko Kawabe & Takanori Yasu

Department of Diabetes and Endocrinology, Dokkyo Medical University Nikko Medical Center, Nikko, Tochigi, Japan

Yuki Nakatani, Nobuyuki Banba & Yasuko Nagashima

Department of Cardiology, Dokkyo Medical University, Nikko Medical Center, Nikko, Tochigi, Japan

Keijiro Kitahara, Naoyuki Otani & Hiroyuki Sugimura

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The study protocol was approved by the Ethics Committee of Dokkyo Medical University Nikko Medical Center (ethical license number Nikko 2015-09). This study was conducted in accordance with the “Declaration of Helsinki” by the World Medical Association and the Sports, Science and Technology and the Ministry of Health, Labor and Welfare (established on December 22, 2014, and partially revised on March 27, 2023). Informed consent was obtained from the patients through an opt-out system, and those who refused to provide consent were excluded.

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Shimoyama, M., Kawamoto, S., Nakatani, Y. et al. Effects of salt intake reduction by urinary sodium to potassium ratio self-monitoring method. Hypertens Res (2024). https://doi.org/10.1038/s41440-024-01655-1

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A Secretive Experiment Released Salt Crystals Over San Francisco Bay—Could It Help Curb Warming?

The technology could make clouds reflect more sunlight, cooling the Earth below. But even the scientists leading the study say letting go of fossil fuels is a much-preferred response to climate change

Christian Thorsberg

Daily Correspondent

Earlier this month, scientists from the University of Washington gathered in semi-clandestine fashion on the deck of a decommissioned aircraft carrier in San Francisco Bay.

Leading an experiment that was intentionally kept under the radar to minimize public backlash, the team started up a high-powered spraying machine and shot microscopic salt aerosol particles hundreds of feet into the morning air.

The trial, meant to test how well these aerosols could travel outside of the lab, is a basis for a much grander future experiment: using the particles to artificially brighten clouds. The innovation could help clouds reflect more light and keep Earth’s surface a little bit cooler.

“If you increase the number of cloud droplets by increasing the number of sea salt particles, it’s like increasing the number of mirrors to reflect sunlight back to space,” Rob Wood , the lead scientist of the university’s Marine Cloud Brightening Program , tells the San Francisco Chronicle ’s Anthony Edwards.

The program’s simulations estimate that brightening 15 percent of the planet’s marine clouds with this method would cool the Earth by about one degree Fahrenheit. But in the real world, uncertainties remain. Getting the correct size and concentration of the particles, for example, is key. Too large or too many, and they’ll contribute to increased precipitation. Too small, on the other hand, and the particles won’t have any noticeable reflective effect.

The test last week took place in Alameda, California, on the USS Hornet , which operates as a Smithsonian Affiliate museum. It was the first cloud brightening experiment ever conducted in North America, and just the second in the world. Four years ago, researchers near Australia’s Great Barrier Reef carried out a similar study in hopes that cloud brightening could protect the region’s corals from bleaching in over-warm waters.

Both experiments fall under the umbrella of geoengineering, a discipline that describes the variety of technological approaches scientists are exploring to help slow or reverse climate change. But the current project—and the field, more broadly—has drawn skepticism for the unknown risks and consequences of tampering with the weather.

“You could well be changing climatic patterns, not just over the sea, but over land as well,” David Santillo , a senior scientist at Greenpeace International who was not involved with the project, tells the New York Times . “This is a scary vision of the future that we should try and avoid at all costs.”

Scientists don’t completely understand some of the possible consequences of launching large amounts of salt aerosols into the atmosphere. For instance, the practice could change ocean circulation patterns or drive unexpected weather—which could, in turn, impact fisheries or farms, writes E&E News ’ Corbin Hiar.

Though the Biden administration has funded research on marine cloud brightening, per the New York Times , the White House noted to the publication that it did not take part in this particular study: “The U.S. government is not involved in the Solar Radiation Modification (SRM) experiment taking place in Alameda, CA, or anywhere else.”

Over the next several months, the team will analyze the results of this study, examining whether the particles maintained the proper size as they entered the atmosphere. Locally, it remains to be seen when and how future experiments will be carried out.

“Since this experiment was kept under wraps until the test started, we are eager to see how public engagement is being planned and who will be involved,” Shuchi Talati , the executive director of the Alliance for Just Deliberation on Solar Geoengineering who did not participate in the experiment, tells E&E News .

Meanwhile, human-fueled changes to climate and weather patterns continue to break monthly and yearly heat records, affecting communities across the globe. Amid these trends, even the scientists leading the experiment agree that curbing fossil fuel emissions—rather than sending additional particles into the atmosphere—is the best course of action.

“I hope, and I think all my colleagues hope, that we never use these things, that we never have to,” Sarah Doherty , an atmospheric scientist at the University of Washington and the manager of its Marine Cloud Brightening Program, tells the New York Times.

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Christian Thorsberg | READ MORE

Christian Thorsberg is an environmental writer and photographer from Chicago. His work, which often centers on freshwater issues, climate change and subsistence, has appeared in Circle of Blue , Sierra  magazine, Discover  magazine and Alaska Sporting Journal .

April 4, 2024

Geoengineering Test Quietly Launches Salt Crystals into Atmosphere

A solar geoengineering experiment in San Francisco could lead to brighter clouds that reflect sunlight. The risks are numerous

By Corbin Hiar & E&E News

An aerial view of a layer of stratocumulus clouds.

SubstanceP/Getty Images

CLIMATEWIRE | The nation's first outdoor test to limit global warming by increasing cloud cover launched Tuesday from the deck of a decommissioned aircraft carrier in the San Francisco Bay.

The experiment, which organizers didn't widely announce to avoid public backlash, marks the acceleration of a contentious field of research known as solar radiation modification. The concept involves shooting substances such as aerosols into the sky to reflect sunlight away from the Earth.

The move led by researchers at the University of Washington has renewed questions about how to effectively and ethically study promising climate technologies that could also harm communities and ecosystems in unexpected ways. The experiment is spraying microscopic salt particles into the air, and the secrecy surrounding its timing caught even some experts off guard.

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"Since this experiment was kept under wraps until the test started, we are eager to see how public engagement is being planned and who will be involved," said Shuchi Talati, the executive director of the Alliance for Just Deliberation on Solar Geoengineering, a nonprofit that seeks to include developing countries in decisions about solar modification, also known as geoengineering. She is not involved in the experiment and only learned about it after being contacted by a reporter.

"While it complies with all current regulatory requirements, there is a clear need to reexamine what a strong regulatory framework must look like in a world where [solar radiation modification] experimentation is happening," Talati added.

The Coastal Atmospheric Aerosol Research and Engagement, or CAARE, project is using specially built sprayers to shoot trillions of sea salt particles into the sky in an effort to increase the density — and reflective capacity — of marine clouds. The experiment is taking place, when conditions permit, atop the USS Hornet Sea, Air & Space Museum in Alameda, California, and will run through the end of May, according to a weather modification form the team filed with federal regulators.

The project comes as global heat continues to obliterate monthly and yearly temperature records and amid growing interest in solar radiation modification from Silicon Valley funders and some environmental groups . It also follows the termination of a Harvard University experiment last month that planned to inject reflective aerosols into the stratosphere near Sweden before it was canceled after encountering opposition from Indigenous groups.

Solar radiation modification is controversial because widespread use of technologies like marine cloud brightening could alter weather patterns in unclear ways and potentially limit the productivity of fisheries and farms. It also wouldn't address the main cause of climate change — the use of fossil fuels — and could lead to a catastrophic spike in global temperatures if major geoengineering activities were discontinued before greenhouse gases decrease to manageable levels.

The University of Washington and SilverLining, a geoengineering research advocacy group involved in the CAARE project, declined interview requests. The mayor of Alameda, where the experiment is being conducted, didn't respond to emailed questions about the project.

The secrecy surrounding the landmark experiment seems to have been by design, according to The New York Times , which, along with a local newspaper, was granted exclusive access to cover the initial firing of the spray cannons.

"The idea of interfering with nature is so contentious, organizers of Tuesday's test kept the details tightly held, concerned that critics would try to stop them," the Times reported. The White House also distanced itself from the experiment, which is being conducted with the cooperation of a Smithsonian-affiliated museum.

The project team has touted its transparency, noting that visitors to the USS Hornet, which now serves as a floating museum, will be able to view the experiment.

"The world needs to rapidly advance its understanding of the effects of aerosol particles on climate,” Kelly Wanser, the executive director of SilverLining, said in a press release. "With a deep commitment to open science and a culture of humility, the University of Washington has developed an approach that integrates science with societal engagement, and can help society in essential steps toward advancing science, developing regulations, promoting equitable and effective decision-making, and building shared understanding in these areas."

The CAARE project is part of a larger coastal study that the University of Washington consortium is planning to pursue. The second phase of that effort would take place on a pier around a mile offshore in a coastal environment, according to a study description the school released Monday.

While a peer review of that proposal was generally positive, the scientists also flagged some transparency shortcomings.

"One reviewer noted that it would help to have more information on the site location," said a Washington-University- commissioned report . "Is there local resistance or concerns (whether founded or unfounded) around issues like local air quality, etc.? How many options exist, and how do different options affect the field study plan?"

The study plan also made no mention of its potential ecological impacts, a key consideration recommended by a 2022 Biden administration marine cloud brightening workshop . That's a significant oversight, according to Greg Goldsmith, the associate dean for research and development at Chapman University.

"History has shown us that when we insert ourselves into modification of nature, there are always very serious unintended consequences," said Goldsmith, who studies the implications of climate change for plant structure and function. "And therefore, it would be prudent to listen to what history has shown and look for consequences."

Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2024. E&E News provides essential news for energy and environment professionals.

Editor’s Note (4/8/24): Our partners at Climatewire have edited this article after posting to clarify that neither Shuchi Talati nor the Alliance for Just Deliberation on Solar Geoengineering is involved in the described solar geoengineering project.

College of the Environment

Marine cloud brightening program studies clouds, aerosols and pathways to reduce climate risks.

Global climate change is about more than just greenhouse gas emissions — among the many complex systems that impact Earth’s climate, one of the most important is how much sunlight is reflected back into space by bright surfaces such as snow, ice and clouds. Clouds play a particularly powerful role in the climate system since they can change rapidly and have a strong effect on Earth’s reflectivity. That’s why researchers with the UW Marine Cloud Brightening Program , an international scientific initiative, are working to better understand clouds, and how both inadvertent and possibly intentional changes to atmospheric particles affect clouds.

“Atmospheric particles, also called aerosols, can have a strong effect on sunlight reflection by clouds,” said Sarah Doherty , program director of the Marine Cloud Brightening Program and a senior research scientist with the UW Cooperative Institute for Climate, Ocean and Ecosystem Studies . “As humans make changes to aerosol emissions, we need a stronger scientific understanding of these effects in order to better understand the potential risks and benefits, and to limit unintended effects.”

The role of clouds and aerosols

When tiny aerosol particles are released into the atmosphere from both natural sources (such as biological emissions and sea spray) and human activities (such as from burning fossil fuels, wood and vegetation) they mix into clouds and can cause them to brighten and reflect more sunlight back into space. This has a cooling effect on the Earth’s climate.

The idea to better understand the role of clouds in climate — and humans’ effect on it — came about when scientists observed that clouds were being made more reflective, or “brighter,” in regions where they were influenced by air pollution.

A particularly striking version of this is seen in “ship tracks,” the trails of brightened clouds along the routes of ships caused by the small aerosol particles their engines emit. The tracks are bright enough and big enough to be observed from space. In order to reduce this pollution and improve global air quality, recent regulations have significantly reduced shipping and other emissions — but in doing so, they have also reduced the reflectivity of clouds, which could be accelerating global warming.

“There’s now strong evidence that reductions in ship emissions starting in 2020 contributed in part to the anomalously warm waters recently observed in the north Atlantic Ocean,” said Robert Wood , professor of atmospheric sciences and lead investigator of the Marine Cloud Brightening Program. “This really speaks to the remarkably strong influence these tiny particles in the atmosphere can exert on clouds and the absorption of sunlight by the Earth. But the truth is that we still don’t have a very good handle on how big of an effect aerosol changes can have globally, because cloud responses to aerosols can vary enormously depending on the type of cloud and on meteorology.”

As scientists investigate these questions, they have also identified new questions: if ship emissions could cause clouds to brighten and reflect sunlight back into space, could a non-polluting version of that phenomenon be used to help cool the planet? And if so, should it?

These are complex topics, and as climate change becomes an everyday reality for people around the world, scientists and governments have recognized the importance of investigating them by recommending further research . In studying the ways that aerosols and clouds interact, the Marine Cloud Brightening Program seeks to inform future decisions by helping humanity understand not just the technical challenges of this kind of climate intervention, but the suite of potential benefits and risks that come along with it.

Understanding marine cloud brightening

Marine cloud brightening (MCB) is one of several proposed climate interventions collectively known as solar radiation modification, or SRM. In this approach, tiny sea salt particles generated from ocean water would be sprayed from ships into areas of low-lying clouds. Once emitted, the particles would remain in the atmosphere for only a few days, brightening clouds over parts of the ocean in order to reduce climate warming.

But before any intervention like this can be considered, it is crucial to fully understand how it will affect the climate system, our oceans and our terrestrial ecosystems.

“The goal of the MCB Program is to understand whether it might even be possible to predictably and reliably brighten low marine clouds, and if so, how doing this in different regions of the globe would affect temperatures, precipitation and climate both globally and locally — as well as any other possible side effects,” said Doherty. “As atmospheric scientists, we think it’s critically important that society has the answers to these questions before making any decisions about whether or not to actually use marine cloud brightening in an effort to reduce climate risks.”

In order to better understand how aerosol particles interact with clouds, and how intentionally brightened clouds would interact with our global climate system, the Marine Cloud Brightening Program researchers are taking a multi-pronged approach.

Computer simulations

The first phases of research have focused on computer modeling. The team is working with models at the global scale to study how aerosol-cloud interactions affect climate, testing the accuracy of their simulations against observations in the field and using them to understand how different MCB implementations would affect future climate. The team is also working with smaller-scale models that simulate the details of clouds to better understand how their reflectivity and other properties are affected by aerosol changes.

“But as with any computer simulations, we need to validate these detailed models against observations because the real world always introduces variables you weren’t expecting,” Doherty said.

Small-scale field studies

To validate the models and measure real-world cloud responses, the team has developed a new approach for controlled studies of aerosol-cloud interactions. That’s where CARI — the cloud aerosol research instrument — comes in.

“In the past when we’ve tried to study how clouds are affected by aerosols, we’ve had to just observe clouds in polluted regions, where it’s difficult to distinguish between changes in the clouds due to aerosols versus other meteorological factors,” said Wood. “Being able to add known quantities of sea salt particles to clouds and compare clouds with different concentrations of aerosols, but that are otherwise the same, will be a powerful new research capability.”

This spring, the Marine Cloud Brightening Program researchers are putting CARI to the test at a new research facility they’ve established onboard the USS Hornet Sea, Air and Space Museum — a Smithsonian affiliate — in Alameda, CA. There they have begun a series of small-scale studies in which CARI generates a sea salt plume, then measures the generated aerosol at multiple points downwind to compare with simulations generated from high resolution models.

Importantly, these studies are not large enough to have any effect on local weather conditions — naturally occurring sea spray from crashing waves along the coast puts more sea salt mass into the air than CARI, which will also only be run for 30 minutes or less at a time. But the researchers’ sensitive instruments will still be able to gather important data from these experiments.

Partnering with the public and other scientists

In addition to revealing new insights about how aerosols interact with clouds, these early outdoor studies are an opportunity to engage with other stakeholders and members of the public.

To that end, the program has established the Coastal Atmospheric Aerosol Research and Engagement (CAARE) facility, also housed at the USS Hornet Sea, Air and Space Museum. Open to scientists, students, community members, government officials, global stakeholders and members of the public, the research site is also an exhibit.

“This research is of the utmost importance to society, so transparency is crucial,” said Maya Tolstoy, Maggie Walker Dean of the UW College of the Environment. “I’m grateful to our researchers and partners for prioritizing engagement with the public, the scientific community and regulators in line with the University of Washington’s commitment to the public good.”

What’s next for marine cloud brightening?

Whether intentional marine cloud brightening should ever be used to address climate risks is a question that requires extensive scientific research, assessment by scientific experts, and informed and equitable decision-making by a global community of stakeholders.

Beyond the scientific questions being addressed by the Marine Cloud Brightening Program, the effort will continue to expand its direct engagement with the public to help inform, educate and receive input on the research. A high degree of openness and engagement is a critical part of the work, given that both pollution aerosols and any human climate intervention have the potential for far-reaching impacts on people, the climate and wildlife.

The researchers are motivated by a stark reality: As climate change worsens, it becomes increasingly likely that society will look to climate interventions such as MCB to help avoid the worst impacts of climate change. The Marine Cloud Brightening Program aims to provide the information needed to understand their potential benefits and risks.

“Improving our understanding of the influence of aerosols on clouds and climate is essential to understanding near-term climate risks, and whether and how marine cloud brightening could help reduce them,” said Doherty. “If we don’t improve our knowledge now, we’ll be flying blind. The international community needs the best information it can get in order to chart a responsible course into a future with a rapidly changing climate.”

Learn more about the Marine Cloud Brightening Program .

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Salt substitution linked with lower risk for dying early, study finds

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Using less salt in your food may seem boring, but the payoffs could be as big as a lowered risk of death, new research has found.

Using a salt substitute when cooking was linked with a lower risk of dying early from any cause or from cardiovascular disease in a new study published Monday in the journal Annals of Internal Medicine.

“We are excited to be able to provide evidence that salt substitutions are effective for improving cardiovascular outcomes when used long-term, up to 10 years,” said the study’s senior author Dr. Loai Albarqouni, an assistant professor at the Institute for Evidence-Based Healthcare at Bond University in Australia. “Previous synthesis tended to focus on short-term outcomes, lasting only two weeks.”

The study is a systematic review of 16 randomized controlled trials that were published before August 23, 2023, and totaled 35,251 participants who were around age 64 on average and had a higher-than-average risk for cardiovascular disease. The trials were mainly in China, with the rest in the United Kingdom, Taiwan, Peru, the Netherlands and Norway.

With two-thirds of the findings coming from China, the authors “were surprised at how little salt substitution research has been conducted outside Asian countries,” Albarqouni said. “This is partially why we have graded the evidence as ‘low to very low certainty’ for Western populations — there simply isn’t enough evidence to verify that salt substitutes would be as effective in the Western context.”

Salt substitution was also linked with a reduction in sodium in urine, and in blood pressure, an effect similar to that of blood pressure medications, the authors found. That could explain the lowered risk of death, Albarqouni said.

The authors acknowledged that in the trials, some of the salt substitutes were not verified and some were purchased by the participants instead of given to them by researchers.

The trials compared the use of common salt — made of about 100% sodium chloride, occasionally with added iodine — with using a salt substitute comprised of 25% to 30% potassium chloride and 60% to 75% sodium chloride.

Another reason why applying the findings to a Western context is difficult is that salt consumption patterns in North America are “driven by processed and takeaway food, while consumption in the research context is more driven by the high amount of salt added during home food preparation,” Albarqouni said.

“This is not the strongest study to base a lot of conclusions on at this point,” said Dr. Andrew Freeman, a preventative cardiologist and director of cardiovascular prevention and wellness at National Jewish Health in Denver. “But it adds to the body of evidence and the signal in the noise that getting rid of sodium salt in your diet is a big plus and getting potassium in your diet is better,”

And “while we know potassium is beneficial, salt is salt,” Freeman, who wasn’t involved in the study, added. “If it’s sodium chloride or potassium chloride or magnesium chloride, it’s all salt. And the best way to get potassium in your body is to eat fruits and vegetables — that’s where potassium is most plentiful.”

Lowering your salt intake

The American Heart Association’s ideal daily sodium limit is 1,500 milligrams per day for most adults, especially those with high blood pressure, and no more than 2,300 milligrams daily.

“If the majority of your food intake is coming from packaged or restaurant food, chances are your sodium intake is too high,” Albarqouni said via email. “There are a few physical signs you may be eating too much sodium, like bloating or swelling, tiredness, high blood pressure, increased thirst and/or urination.”

If you’re concerned about your intake, you can seek medical or nutrition advice from a professional, Albarqouni added.

When buying packaged food, check the sodium content on labels. Some foods can contain more sodium than you think, such as poultry or cereals, Freeman said. One standard-size pickle typically has around 1,500 milligrams of salt, he added.

Besides lowering salt consumption by simply eliminating salt in your home cooking, you can also try purchasing salt substitutes with a composition like the ones used in the study or using salt-free seasonings to add more flavor to food instead, experts said.

The authors acknowledged that more research is needed to confirm whether salt substitution of the study’s kind is safe for patients “sensitive to micronutrient manipulation,” including those sensitive to potassium — such as people with renal deficiency, they said.

Food with less salt may taste boring at first, but your tastebuds can adjust within just a couple of weeks, Freeman said, so give yourself time to adjust.

“It’s also important to remember that reducing sodium intake is just one way to reduce cardiovascular risk without medication,” Albarqouni said. “Things like diet changes, stopping smoking and increasing movement can also have an impact. Salt substitutes are not a holy grail to eliminating cardiovascular disease, but are one piece of the puzzle that can help.”

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Home / 2024 / April / Salt Marsh Restoration Study

UC Santa Cruz researchers value salt marsh restoration as a crucial tool in flood risk reduction and climate resilience in the San Francisco Bay

April 11, 2024

By Elisa Smith

Salt marsh restoration can mitigate flood risk and bolster community resilience to climate change in our local waterways, according to a recent study published in Nature by a postdoctoral fellow with UC Santa Cruz’s Center for Coastal Climate Resilience (CCCR). 

The study, titled “The value of marsh restoration for flood risk reduction in an urban estuary,” explores the social and economic advantages of marsh restoration amidst the growing threats of sea level rise and storm-driven flooding. Climate change will put many communities at risk. In California, some of the study co-authors from the U.S. Geological Survey (USGS) have shown that 675,000 people and $250 billion in property are at risk of flooding in a scenario with 2 m of sea level rise combined with a 100-year storm. Flooding due to sea-level rise is amplified by storms, which drive higher coastal water levels via surges, waves, and increased river discharge, along with increasing coastal population density. 

To simulate marsh restoration, the research team used a hydrodynamic model of San Francisco Bay, focusing on San Mateo County, the county most vulnerable to future flooding in California. The team ran computer simulations of the county’s shoreline during storms, with and without marsh restoration, and worked closely with local flood managers and planners to incorporate their input into the model. 

“The Bay Area is low-lying and densely populated, thus at significant risk for future climate change impacts, and home to really large areas of degraded habitat. We have found compelling evidence that marsh restoration can reduce flood risk to people and property locally, providing both community and ecosystem co-benefits,” said CCCR fellow Rae Taylor-Burns, whose research also appears in a Springer Nature blog. 

Key findings from the study include:

• Identification of priority areas in San Mateo County for salt marsh restoration to maximize socio-economic impacts in reducing flood risk. 
• Development of a detailed flood model to evaluate the risk of flooding with and without salt marshes locally, aiding in the planning and design of restoration projects.
• The monetization of flood risk reduction benefits to identify cost-effective investments in marsh restoration, potentially attracting public and private funding.

The study underscores the broader implications of wetland restoration beyond flood protection, including carbon sequestration, habitat preservation, and recreational opportunities. It also makes the case for investments in nature-based solutions and community resilience that can help lessen future climate change impacts. 

Researchers show the benefits of integrating salt marsh restoration into comprehensive climate resilience strategies in San Mateo County and estuaries worldwide that are facing similar threats. This could include funding from FEMA grant programs or Regional Measure AA, which provides approximately $500 million for marsh restoration throughout the San Francisco Bay. This work also supports identifying CA coastal wetlands as critical national infrastructure, as the Center has helped support coral reefs in Guam, Hawai’i, Puerto Rico, and the U.S. Virgin Islands.

“As we confront the escalating challenges posed by climate change, it is imperative that we explore innovative solutions to enhance community resilience," said Michael W. Beck, director of the Center for Coastal Climate Resilience and a co-author of the study. “Salt marsh restoration represents a nature-based approach that can complement traditional infrastructure and safeguard our coastal communities."

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Geospatial characterization of salt marshes in Connecticut (ver. 2.0, April 2024

This data release contains coastal wetland synthesis products for the state of Connecticut. Metrics for resiliency, including the unvegetated to vegetated ratio (UVVR), marsh elevation, tidal range, wave power, and exposure potential to environmental health stressors are calculated for smaller units delineated from a digital elevation model, providing the spatial variability of physical factors that influence wetland health. The U.S. Geological Survey has been expanding national assessment of coastal change hazards and forecast products to coastal wetlands with the intent of providing federal, state, and local managers with tools to estimate the vulnerability and ecosystem service potential of these wetlands. For this purpose, the response and resilience of coastal wetlands to physical factors need to be assessed in terms of the ensuing change to their vulnerability and ecosystem services. This project has been funded in part by the United States Environmental Protection Agency under assistance agreement DW-014-92531201-1 to N. Ganju.

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Related content, kate ackerman, zafer defne, phd, oceanographer, neil kamal ganju, phd, research oceanographer.

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Sodium Intake and Health: What Should We Recommend Based on the Current Evidence?

Andrew mente.

1 Population Health Research Institute, Hamilton Health Sciences, Hamilton, ON L8L 2X2, Canada; [email protected] (M.O.); [email protected] (S.Y.)

2 Department of Health Research Methods, Evidence and Impact, McMaster University, Hamilton, ON L8S 4L8, Canada

Martin O’Donnell

3 HRB-Clinical Research Facility, National University of Ireland, H91 TK33 Galway, Ireland

Salim Yusuf

4 Department of Medicine, McMaster University, Hamilton, ON L8S 4L8, Canada

Associated Data

Not applicable.

Several health organizations recommend low sodium intake (below 2.3 g/day, 5.8 g/day of salt) for entire populations, on the premise that lowering of sodium intake, irrespective of its level of intake, will lower blood pressure and, in turn, will result in a lower incidence of cardiovascular disease. These guidelines were developed without effective interventions to achieve long term sodium intakes at low levels in free-living individuals and without high-quality evidence that low sodium intake reduces cardiovascular events (compared with average levels of intake). In this review, we examine whether advice to consume low amounts of sodium is supported by robust evidence. We contend that current evidence indicates that most people around the world consume a moderate range of dietary sodium (3 to 5 g/day), that this level of intake is associated with the lowest risk of cardiovascular disease and mortality, and that the risk of adverse health outcomes increases when sodium intakes exceeds 5 g/day or is below 3 g/day. While the current evidence has limitations, it is reasonable, based upon prospective cohort studies, to suggest a mean target of below 5 g/day in populations, while awaiting the results of large randomized controlled trials of sodium reduction on cardiovascular disease and death.

1. Introduction

Several health organizations recommend low sodium intake (<2.3 g/day, ~1 teaspoon of salt) for the entire population [ 1 , 2 , 3 ], a level that has not been achieved by any modern population in the world. The advice to lower sodium to such low levels is based on the premise that lowering sodium intake, irrespective of its current intake levels, will lower blood pressure, which in turn, will lead to reductions in cardiovascular events and deaths. In this framework, it is assumed that extreme lowering of sodium in entire populations is practical, will be beneficial, and will have no harm [ 4 ]. However, there is no evidence that it is feasible to sustainably lower sodium in entire populations to low intake levels, and further, the evidence linking sodium consumption with cardiovascular disease has been inconsistent, with no study reporting lower risk of cardiovascular events with low sodium intake (below 2.3 g/day). Therefore, these recommendations have resulted in considerable controversy about what the optimal level of sodium intake should be for good health.

Sodium is an essential nutrient, meaning that it is required for normal body function and health, and therefore expected to have a physiologic ‘healthy’ range of intake, as with other essential electrolytes [ 5 , 6 ]. Most populations globally (≈95%) consume in the range of 3 to 6 g of sodium daily, which means that the current recommended levels of below 2.3 g/day of sodium by entire populations is well below the range of the majority of the world’s experience [ 7 ]. Furthermore, these guidelines were developed without evidence that it would be possible to reduce sodium to such low levels on a prolonged basis in entire populations or that such as strategy will lower cardiovascular events or death. Current evidence from cohort studies suggests a J-shaped relationship between sodium intake and cardiovascular events, as would be expected for an essential nutrient [ 6 , 8 ], and suggests that the lowest risk of death or cardiovascular disease occurs in populations consuming an average sodium intake (3 to 5 g/day) [ 9 , 10 , 11 , 12 , 13 ]. To date, no study (observational or randomized trial) has demonstrated a significantly lower risk of cardiovascular events with low sodium intake (below 2.3 g/day) compared with average intake [ 14 ].

In this review, we assess whether the recommendation for low sodium intake is supported by robust evidence. We contend that current evidence indicates that most populations globally consume a moderate range of dietary sodium (3 to 5 g/day), that this level of intake is associated with the lowest cardiovascular risk (and so is optimal), and that cardiovascular disease risk increases when sodium intakes exceeds 5 g/day or is below 3 g/day ( Figure 1 ).

Conceptual diagram of health risk by sodium intake levels based on the current evidence. The lowest risk range (i.e., “sweet spot”) for sodium intake is at ~3 to 5 g/day, with both lower and higher levels of intake associated with higher risk of cardiovascular disease or death. The Dietary Guidelines for Americans (DGA) recommendation for sodium corresponds with a higher risk of adverse health outcomes.

2. Sodium and Physiology

The importance of sodium to human physiology suggests that its relationship with health is likely to have a “sweet spot” (i.e., a J-shaped relationship), meaning that too little or too much is expected to have adverse health consequences [ 15 ]. Sodium is the most important extracellular cation in the body, required for many physiologic processes, and is tightly regulated by many processes (renal, biochemical, endocrine, immune, and neural), to maintain blood sodium within a normal range [ 5 , 6 , 16 ]. Thus, although short-term extreme reductions in sodium intake are possible in controlled settings for short periods, this is unlikely to be sustainable in free living individuals in the long term [ 17 ]. In the majority of people with normal kidney function and blood pressure (BP), the kidney is sufficiently able to deal with wide variations in sodium intake, without eliciting increases in BP. However, in some individuals, moderate changes (1 to 2 g/day) in sodium intake can result in marked increases in BP, a concept called salt sensitivity [ 18 ]. This can be mitigated by a high potassium diet [ 19 ].

Sodium restriction is increasingly shown to activate the renin–angiotensin–aldosterone system (RAAS), which itself is associated with increased cardiovascular risk [ 20 , 21 ]. Two systematic reviews of studies examining sodium restriction and RAAS activity, catecholamines, and lipids reported an increase in renin and aldosterone and catecholamine activity [ 22 , 23 ]. Despite the many available studies (167 in one review), most studies had few participants (usually under 50 individuals), with short duration of follow-up (28 days among people with hypertension, and only 17 days in people without hypertension). Therefore, the sustained long-term effects of low sodium intake on these cardiovascular biomarkers require further study.

Some hunter gatherer populations living in remote settings (e.g., the Amazon Forest) are reported to have a very low sodium intake and low rates of hypertension. However, the measurement of sodium intakes in these populations may not have been accurate, and there is an observed excessive activation of the RAAS system in these populations [ 24 ], which may have an adverse effect on health [ 20 , 25 ]. Given their relatively short mean life expectancy (e.g., 40 years), the long-term effects of low sodium intake on health in these populations are unknown [ 24 ].

3. History of Sodium and Health

It has been theorized that paleolithic humans consumed below 1 g of sodium daily (a claim that is impossible to verify), and that the current mean sodium intake (4 g daily) in human populations is a recent phenomenon (i.e., emerging in the last few millennia) [ 26 ]. However, these assertions are unproven, and assume that these people consumed no fish or shellfish, that seawater was not used in food preparation, and that no salt was used to preserve foods. The true amount of sodium consumed by paleolithic humans is unknown, and any estimates are likely wild guesses.

Salt has been instrumental in the transition from hunter gatherer to settled communities, as it allowed the preservation of perishable food during the winter. Salt became an early trading commodity. The word ‘salary’ (from the Latin ‘salarium’) originated as monthly allowance to Roman soldiers to purchase salt, indicating its importance to society. Gandhi stated that “next to water and air, salt is perhaps the most vital to health” [ 27 ].

Internationally, the countries with the highest average life expectancy are many of those with the highest average sodium intake [ 28 ]. In recent decades, dietary sodium consumption from non-discretionary sources (hidden within foods) has been gradually increasing, particularly in high-income countries [ 29 ]. However, sodium intake is tightly regulated through a central neural mechanism, which appears to account for the stable mean sodium intake in populations, despite changes in sodium food sources [ 5 , 15 ].

4. Global Sodium Intake

Most people around the world consume a sodium intake in the range of 3 to 6 g/day with fewer than 5–10% consuming below 2.3 g/day, so human experience with the currently recommended low sodium levels is limited [ 7 ]. This would also mean that the majority of people in the world will require large changes to their diets to achieve the current recommendations.

Globally, based on a meta-analysis of surveys from 187 countries by the Global Burden of Disease (GBD) collaboration, the mean intake of sodium was estimated at 3.95 g/day [ 7 ]. From the INTERMAP study [ 29 ], intakes are highest in Eastern Europe, Central Asia, and East Asia (mean intakes above 4.2 g/day). The highest mean intakes were found in the Beijing sample, Northern China, up to 6.9 g/day in men and 5.8 g/day in women. In comparison, in the United States, mean sodium intakes for the eight population samples ranged from 4.1 to 4.4 g/day in men and 3.0 to 3.5 g/day in women.

5. Can We Measure Sodium Intake Adequately?

A key challenge in identifying the optimal sodium intake is the lack of a valid and reliable method to objectively quantify sodium intake in a large number of people. The use of multiple 24-h urine collections is sometimes stated to be the reference method, but this approach can be unreliable, as a high proportion of individuals do not comply with the requirement to provide complete urine collections on multiple occasions—a limitation that invalidates this measurement for most studies or assessment of sodium intake in large population studies [ 30 ]. (It should be noted that in a recent study by the U.S. Centers for Disease Control, 30% of individuals were not able to provide even a single complete collection of urine) [ 31 ].

For population-level studies, given that incidence of cardiovascular events and death in healthy populations are low (about 1% annually), very large sample sizes (several tens or even hundreds of thousands of individuals) are needed to be enrolled and followed for a decade or more to detect modest sized differences in risk for clinical events (e.g., a stroke or heart attack) in those with average vs high sodium intake. Estimating mean intakes in populations is more feasible using a validated calculation formulae from single fasting urine samples (e.g., Kawasaki method with a fasting morning sample) [ 32 , 33 ]. While this approach is not appropriate for assessing sodium intake of individuals in a clinical setting, it has been used for estimating sodium intake in large groups of people epidemiologic studies [ 11 , 34 ]. For example, the PURE study examined sodium intake in over 100,000 individuals based on formula-derived estimates of 24-h urinary sodium excretion from a single fasting urine sample and found a positive association with systolic BP of 2.11 mmHg per g of sodium [ 11 , 35 ], which is consistent with randomized trials of sodium reduction and BP (i.e., 2.42 mmHg reduction in systolic BP per 1 g of sodium lowering) [ 20 ] and is stronger than associations reported in observational studies using 24-h urine collections (i.e., 1.0 mmHg change in systolic BP per 1 g of sodium in INTERSALT, 0.22 mm Hg per 1 g in INTERMAP, and ‘null association’ in the Scottish Heart Study) [ 36 , 37 , 38 ]. These findings strongly indicate that formula-derived estimates of 24-h urinary sodium excretion from fasting urine samples may even be superior to capturing ‘usual’ sodium intake than 24-h urine collections for use in large population studies. (Note that the fasting morning urine sample differs from so called “spot urine“ and the distinction is akin to the difference between a fasting blood glucose level vs a random blood glucose value).

6. Sodium Intake and Blood Pressure

Current guidelines recommendations for low sodium intake, to under 2.3 g/day, are based solely on studies linking sodium intake with BP in short term intervention trials.

6.1. Observational Studies

Overall, there is convincing epidemiologic evidence of a positive, curvilinear association of sodium intake and BP in populations. INTERSALT, the first large international study of sodium and BP, included people aged 20–50 years from 52 centres in 39 countries ( n = 10,079) who completed a 24-h urine collection. The INTERSALT study [ 36 ] reported in 1988 a weak positive association of sodium intake with BP in 33 of 53 centres (which was statistically significant in eight). Another large study in Scotland ( n = 7354) published at the same time found no association between sodium intake and BP [ 37 ], which was confirmed later in the INTERMAP study [ 38 ].

The largest international study of sodium intake and BP was the PURE study [ 35 ], which included more than 102,000 adults from 18 countries. PURE reported a positive, threshold association of sodium intake with BP (2.11/0.78 mmHg increment in BP per 1 g daily increase in sodium), which was only statistically significant for sodium intakes above 3 g/day and was strongest in those with consumption exceeding 5 g/day (2.58 mmHg increment in BP per 1 g increase in sodium) [ 35 ]. The associations were stronger in older people, those with hypertension and those consuming low amounts of potassium. The largest cohort study of sodium intake and BP was the recent UK-Biobank study ( N = 322,624) [ 34 ], which also found higher BP with higher sodium intake.

6.2. Randomized Controlled Trials

The impact of sodium intake on BP has been evaluated in numerous clinical trials. Most were short-term trials (95% with less than 6 months duration) with relatively few participants [ 22 , 23 ].

Meta-analyses of clinical trials have found mean reductions in BP with sodium lowering that are generally in keeping with the results from cohort studies [ 22 , 23 ]. In one meta-analysis (36 clinical trials; n = 6736), sodium lowering (by an undisclosed amount) was associated with a 3.39/1.54 mmHg reduction in BP, which was greater in people with hypertension than those without hypertension (−4.06/2.26 mmHg vs. −1.38/0.58 mmHg, respectively) [ 39 ]. Analyses of the results by differing duration of follow-up reported that the reductions in BP attenuated over time. For example, the between-group differences in BP decreased in a graded fashion with longer follow-up duration (−4.07/1.67 mmHg for the 31 trials of below 3 months duration, −1.91/1.33 mmHg for the five trials of 3–6 months duration, and −0.88/0.45 mmHg for the three trials of more than 6 months duration) [ 39 ]. These data demonstrate the near impossibility of achieving and sustaining a low sodium intake (<2.3 g/day) in free-living populations, even with intense dietary counselling.

The DASH-Sodium trial was the largest ‘feeding’ clinical trial of sodium and BP [ 40 ] (a feeding trial is one in which all foods that individuals eat are provided for the 30-day duration of the experiment). This was a 3 × 2 factorial trial of 412 participants with pre-hypertension that evaluated three different levels of sodium intake (targeting 1.5, 2.5 and 3.3 g/day) consumed for only 30 days and compared a DASH diet pattern with a control diet (i.e., an all-around low-quality diet). The BP reduction with sodium lowering was two to three times greater in those consuming the control diet, in which the background potassium intake (1.6 g/day) was well below that of a typical US diet (2.6 g/day) [ 41 ], which may have enhanced the effects of sodium reduction on BP in the trial [ 42 ]. The findings from the trial have been influential on recommendations to lower sodium intake to below 2.3 g/day and ideally to 1.5 g/day for the entire adult population. However, there are no data that such large reductions in sodium intake would be seen in real-life situations or over a longer period (e.g., in the larger TOHP study where overweight people with borderline elevated BP were counselled to reduce sodium and to eat a healthy diet, the effects over 36 months were very small; systolic BP difference between sodium intake groups was only 1.2 mmHg) [ 43 ].

In the TOHP-II trial [ 43 ], the largest trial ( n = 2382) of longer-term sodium reduction and BP (36 months follow-up duration), the mean sodium intake achieved was 3.1 g/day at 18 months and 3.2 g/day at 36 months, despite intensive dietary counselling targeting a sodium intake of <1.8 g/day in the intervention group. This result indicates that a target of <2.3 g/day is not achievable even with intensive efforts to lower sodium in the controlled setting of a clinical trial. The control group had a mean sodium intake of 3.9 g/day at 18 months and 4.0 g/day at 36 months [ 43 ].

These studies demonstrate the near impossibility of achieving, and sustaining a low level of sodium intake (below 2.3 g/day) over a few years, in free-living populations, even with intensive dietary counselling.

7. Sodium and Cardiovascular Events

7.1. observational studies.

Numerous cohort studies have examined associations of sodium intake with cardiovascular disease and total mortality [ 44 ]. Most reviews of these studies compared extremes of sodium intake (i.e., the lowest vs highest intake categories) and assumed a linear relationship [ 39 , 45 ]. By contrast, Graudal et al. [ 10 ] evaluated the totality of data, including all levels of sodium intake, and found a J-shaped association of sodium consumption with cardiovascular disease and total mortality, with an increased risk of events both above 5 g/day and below 2.7 g/day, in comparison with moderate levels of intake (2.7 to 5 g/day). These findings were consistent across methods of sodium estimation.

Since the meta-analysis by Graudal, two large prospective studies have been published [ 11 , 34 ], the PURE international study ( n = 101,945 participants, follow-up of 7.2 years) [ 11 ] and the UK-Biobank ( n = 322,624 participants, follow-up of 7.0 years) [ 34 ], both of which employed formula derived estimates of 24-h sodium excretion. The PURE study found a J-shaped association between sodium excretion and cardiovascular disease and total mortality, with lowest risk of events found between 3 and 5 g per day, supporting the previous meta-analysis [ 10 ]. The increased risk associated with high sodium intake (above 5 g/d) was largely confined to those with hypertension [ 11 ], a finding consistent with the PREVEND study [ 46 ]. PURE also showed that in those with high potassium intake and higher-quality diets, the association of high sodium and cardiovascular events was mitigated [ 47 ]. The UK-Biobank study reported no significant association between sodium excretion and cardiovascular events, but a suggested J-shaped association was found with mortality [ 34 ].

The higher risk for cardiovascular events or death with low sodium intake, compared to average intake, has been seen in studies conducted by several different investigators from over 50 countries [ 11 , 12 , 34 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ] (e.g., PURE [ 11 , 53 , 54 ], ONTARGET/TRANSCEND [ 11 , 51 ], EPIDREAM [ 11 ], EPIC-Norfolk [ 12 ], NHANES-I, II and III [ 55 , 56 , 57 ], FLEMENGHO/EPOGH [ 50 ], SURDIAGENE [ 52 ], PREVEND [ 46 ], and CRIC [ 58 ] studies), and has been found in those with and without vascular disease, those with and without diabetes, and those with and without hypertension, and has been observed despite extensive statistical adjustments for confounders and extensive efforts to avoid “reverse causation”. These findings have also been seen in studies using different methods of sodium estimation, including repeated 24-h urine, single 24-h urine, an overnight urine, and dietary assessment.

In 2019, the report by the National Academies of Sciences, Engineering, and Medicine (NASEM) [ 3 ] did not take into consideration the evidence from the above cohort studies and meta-analyses that found an increased risk of death or cardiovascular disease events with low sodium intake (J-shaped or inverse association). Instead, the report focused on the observational follow-up data from the control group in the TOHP trial ( n = 2275 participants; 193 vascular events or deaths) [ 61 ]. The NASEM report concluded that sodium intake and cardiovascular disease show a linear association, although there was no significant difference in risk comparing those with low sodium intake (below 2.3 g/day) to moderate sodium intake (3 to 5 g/day), and so therefore the conclusions were not supported by evidence of a statistical difference between these intake groups [ 61 ]. In 2017, a technical report from the World Heart Federation, European Society of Hypertension and European Public Health, considered the same information and concluded that the evidence supported sodium-intake reduction only in populations consuming high sodium intake (above 5 g/day), incorporated within a healthy overall diet pattern.

Collectively, there is no robust evidence that lowering sodium below an intake of 3 g/day is likely to lead to a lowering of cardiovascular disease or death compared to a sodium intake of 3 to 5 g/day. There are, however, concerns that sodium intake below 3 g/day may be associated with a higher risk of death compared to intakes between 3 and 5 g/day.

7.2. Randomized Controlled Trials

Randomized trials to specifically determine the effect of low sodium intake (i.e., below 2.3 g/day) compared to moderate intake on clinical outcomes are still not available.

Meta-analyses of BP trials that reported cardiovascular events have arrived at differing conclusions. One Cochrane collaboration of trials reporting on cardiovascular outcomes concluded that ‘there is insufficient power to confirm clinically important effects’, but reported a 19% lowering of CVD in one analysis of six clinical trials ( n = 5762) with no significant lowering of mortality [ 62 ]. However, this result was dependent entirely on one study [ 63 ], a cluster randomized trial with few clusters which may result in poor randomization and bias. Excluding this trial makes the results of the meta-analysis nonsignificant [ 62 ].

Importantly, these meta-analyses do not specifically address the impact of low sodium intake (below 2.3 g/day), since the two largest studies in the review (i.e., the observational follow-up of the TOHP-II trial and the trial by Chang et al.), did not achieve the currently recommended target of low sodium intake in the intervention groups. Moreover, the TOHP trial had 23% of participants lost to follow-up for cardiovascular outcomes, but follow-up was complete for mortality–for which no difference in events was observed [ 64 ].

Thus, the current evidence is inconclusive as to whether lowering sodium in the diet will reduce CVD, and until we have large clinical trials, the issue will remain unresolved.

7.3. Is Sodium Lowering in Populations and Individuals to Recommended Levels Feasible?

Some countries with relatively high mean sodium intakes (above 4 g/day) have shown a lowering of sodium intake. For example, in China, where sodium consumption exceeds that of most countries (above 5 g/day), marked reductions in sodium intake were reported over time (from 6.7 g/day in 1991 to 4.8 g/day in 2009), mainly due to lowering of salt intake at the table or during cooking [ 65 ].

By contrast, in countries with more moderate sodium intakes (3 to 4 g/day), there is less clear evidence that population-level interventions result in lowered sodium intake. In the UK, one study reported a reduction in average sodium intake by 0.6 g/day from 2000 to 2011, during which some strategies tailored to lower sodium intake were put into action [ 66 ]. However, according to a UK report from 2008, during which time a salt reduction program was fully established, no significant lowering of sodium consumption was reported [ 67 ]. Globally, average sodium intake did not decrease during a 20-year period (from 1990 to 2010) [ 7 ].

Some guidelines have joint targets for sodium (below 2.3 g/day) and potassium (above 3.5 g/day) intakes [ 3 ]. However, since intake of these electrolytes is positively correlated [ 68 ], the current combined sodium-potassium target has been nearly impossible to achieve in general populations (less than 0.1% of the population had diets that met the joint guideline target) [ 47 ]. In addition, targeting a very low sodium intake may have implications for overall dietary quality. An analysis of the NHANES cohort suggests that achieving an overall high-quality diet is more difficult with sodium intake of below 2.3 g/day than with higher sodium intakes [ 69 ].

Overall, we have no evidence that lowering sodium to very low levels (<2.3 g/day) in entire populations is feasible, safe, or beneficial.

8. Implications for US Dietary Guidelines

The Dietary Guidelines Advisory Committee (DGAC) classifies sodium as a “nutrient of concern”, based on the belief that Americans consume an excessive amount [ 70 ]. While the DGAC states that it “concurs” with the 2013 IOM Report that there is insufficient evidence to support a recommendation of lowering sodium to below 2.3 g/day [ 71 ], their conclusions directly contradict the report. In particular, the DGAC does not address the IOM’s conclusion that sodium intake below 2.3 g/day may lead to adverse health outcomes in both healthy and at-risk populations including people with vascular disease and diabetes, a population that includes tens of millions of Americans. Instead, the DGAC recommends that sodium intake among adults should be no more than 2.4 g/day, despite a lack of evidence showing that these amounts are effective and safe, compared to the average (moderate) intake range.

9. Conclusions

At present, recommendations to reduce sodium intake in whole populations to low levels is premature. This conclusion was repeated in two recent reviews by a group of experts (with diverse opinions and backgrounds) [ 14 , 72 ]. Of note, the results of several clinical trials of low sodium intake are expected in a year or two. These trials will hopefully clarify the amounts of sodium that are compatible with better health.

We suggest that, until new data emerge (ideally from large clinical trials), the optimal sodium intake should be in the range between 3 and 5 g/day. Most Americans (i.e., about four out of five people) have sodium intakes below 5 g/day, and in these individuals there is little evidence that lowering sodium will reduce cardiovascular events or death. Therefore, efforts to reduce sodium intake in entire populations cannot be justified. A more appropriate strategy would be to use targeted approaches directed at individuals consuming high amounts of sodium (>5 g/day), which, in the US, may also be diets with high intakes of processed foods, where the focus should be on overall health dietary patterns. At-risk individuals, especially the elderly and people with hypertension, it is reasonable to suggest avoiding excessive sodium intake (i.e., >4 g/day), in the absence of orthostatic intolerance syndromes.

Most countries of the world have average intakes within the lowest risk range, with the United States in the lower part of this range (~3.5 g/day). A few countries such as China have average intakes that correspond with higher risk (>5 g/day) and would likely benefit from reducing sodium intake to the “sweet spot” levels.

Author Contributions

Conceptualization, A.M., M.O., S.Y.; writing—original draft preparation, A.M.; writing—review and editing, M.O. and S.Y.; visualization, A.M., M.O., S.Y.; All authors have read and agreed to the published version of the manuscript.

This research received no external funding.

Institutional Review Board Statement

Informed consent statement, data availability statement, conflicts of interest.

The authors declare no conflict of interest.

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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The Surprising Connection Between Male Infertility and Family Cancer Risk

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In a recent study , researchers at Huntsman Cancer Institute at the University of Utah (the U) found a surprising trend in families with male infertility: an increased risk of certain cancers. This discovery could lead to a more personalized approach to cancer risk assessments, making cancer prevention more effective.

According to the National Institutes of Health, around 9% of men at reproductive age have experienced fertility problems .

“We know that men who experience infertility tend to have more health issues like cardiovascular disease, autoimmune conditions, earlier mortality, chronic health conditions, and cancer,” says Joemy Ramsay, PhD , the study's lead investigator, researcher at Huntsman Cancer Institute, and assistant professor in the Division of Urology at the U. “We wanted to look at whether the family members of these men were at higher risk for these conditions.”

Ramsay has a background in public health, specializing in occupational and environmental exposure. This study represents the first step in determining family members’ correlated risk levels to diseases, such as cancer. Ramsay explains that since family members share similar genetic factors, environments,  and lifestyles, it would be easier to identify other things impacting their cancer risk. Once general risk has been assessed, etiological factors can be more accurately evaluated in determining the part they play in a diagnosis.

Using the Utah Population Database , one of the world’s richest sources of genetic and public health information, Ramsay and her team, which included Heidi Hanson, MS, PhD , Nicola Camp, PhD , and Myke Madsen , looked at parents, siblings, children, and even aunts, uncles, and cousins, of men who have been diagnosed with infertility.

“It is important to have these conversations with our families and bring your concerns to your medical team.”

By observing several types of cancer at once, the team was able to develop an algorithm that clusters similar things together. This algorithm made it possible to identify roughly 13 characteristic patterns. The patterns were based on families possessing similar multi-cancer risks, instead of looking at only one cancer type at a time.

“Both cancer and subfertility are complex diseases and processes,” says Ramsay. “This method helps create similar family groups, making it easier to uncover the reason behind a family being at high risk for certain diseases over others.”

For families with male infertility, these findings may prompt additional conversations with their doctors.

“While the link is still not fully understood, it is important to have these conversations with our families and bring your concerns to your medical team,” says Ramsay.

Further research is needed to continue to establish a link between male infertility and cancer risk. Understanding the reason behind a risk may ultimately lead to more personalized courses of treatment, screening, and prevention.

Huntsman Cancer Institute leads the way in educating patients on how to prevent and treat cancer. For more information on genetic testing, visit our Family Cancer Assessment Clinic .

This study was supported by the National Institutes of Health/National Cancer Institute including P30 CA042014 and Huntsman Cancer Foundation . The chatbots were developed in a recently completed trial funded by the Inherited Cancer Syndrome Collaborative of the Cancer Moonshot initiative.

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Heather Simonsen Public Relations Huntsman Cancer Institute Email Us 801 581-3194

About Huntsman Cancer Institute at the University of Utah

Huntsman Cancer Institute at the University of Utah (the U) is the National Cancer Institute-designated Comprehensive Cancer Center for Utah, Idaho, Montana, Nevada, and Wyoming. With a legacy of innovative cancer research, groundbreaking discoveries, and world-class patient care, we are transforming the way cancer is understood, prevented, diagnosed, treated, and survived. Huntsman Cancer Institute focuses on delivering a cancer-free frontier to all communities in the area we serve . We have more than 300 open clinical trials and 250 research teams studying cancer at any given time. More genes for inherited cancers have been discovered at Huntsman Cancer Institute than at any other cancer center. Our scientists are world-renowned for understanding how cancer begins and using that knowledge to develop innovative approaches to treat each patient’s unique disease. Huntsman Cancer Institute was founded by Jon M. and Karen Huntsman.

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