Sodium Reduction
By Densie Webb, PhD, RD
Today’s Dietitian
Vol. 25 No. 6 P. 20
Learn about the World Health Organization’s latest report, recommended intakes, and expert strategies to lower consumption.
The World Health Organization (WHO) recently released a report titled, “WHO Global Report on Sodium Intake Reduction,” which concluded that implementing sodium reduction policies internationally could save an estimated two million lives by 2025 and seven million lives by 2030.1 WHO’s prediction is based on the well-established fact that high sodium intake contributes to hypertension, which is considered a valid surrogate for risk of CVD, the number one killer in the United States for men and women.2 It’s also well recognized that hypertension can lead to stroke, kidney disease, heart attack, and heart failure. In fact, hypertension-related illness is the leading cause of mortality, not only in the United States but also worldwide, making blood pressure control a critical health issue.3 Reducing dietary sodium is an important dietary therapy for reducing risk.
Here’s the latest on reducing hypertension-related illnesses by lowering sodium intake.
Sodium Intake and Risk of Hypertension
A high-sodium diet is associated with alterations in various proteins responsible for calcium homeostasis and myocardial contractility.4 While population and clinical studies for decades have found that lowering dietary sodium reduces blood pressure and lowers risk of cardiovascular complications, several recent clinical studies and meta-analyses have reexamined and reinforced the evidence. “The association of blood pressure and salt intake is very strong,” says Daniel T. Lackland, DrPh, FAHA, FACE, a professor in the department of neurology at the Medical University of South Carolina and director of the Division of Transitional Neurosciences and Population Studies.
A recent systematic review and meta-analysis of nine studies involving 645,000 participants concluded that sodium intake and cardiovascular events exhibited a dose-response association. For every 1 g increase in sodium intake, there was a greater risk of cardiovascular events by up to 4%.5 Elliott M. Antman, MD, a professor of cardiovascular medicine at Harvard Medical School, emphasizes that the modeling in the study is “an expression of a population level effect of sodium vs cardiovascular events. It’s expected that some individuals will have greater or lesser responses than the average response in the population.”
Despite the overwhelming evidence of an association between sodium intake and elevated blood pressure, some researchers have promoted the idea that reducing sodium doesn’t consistently reduce CVD and that reducing sodium may increase the risk of CVD.
“The media and medical journals emphasize studies that demonstrate controversial findings,” says JoAnne Arcand, PhD, RD, an associate professor and Research Excellence Chair in Nutrition Policy and Implementation Science at Ontario Tech University in Oshawa, Ontario, Canada. “It heightens reader interest. However, this practice becomes concerning when the controversial studies are observational in nature, which does not prove cause and effect, or when studies have used scientific approaches that lack scientific rigor.”
Antman agrees: “There have been several confusing and flawed studies that questioned the benefits of lowering sodium intake. Hopefully, an authoritative body, such as WHO, will provoke the shift that’s needed to help drive down noncommunicable disease rates by lowering sodium intake.”
Additional Health Risks
While high blood pressure is the primary health risk associated with a diet high in sodium, a growing body of evidence cited in the WHO report documents the impact of high sodium intakes on other health risks, including gastric cancer, obesity, Ménière’s disease, and osteoporosis.6-10 Sodium—both high and low intakes—also has been implicated as a contributing factor for causing or possibly reducing the risk of COVID-19 infections.11 But the consensus is that more research is needed regarding the association sodium intake has on health conditions other than CVD.
Reducing Sodium in the Diet vs the Food Supply
While RDs can provide guidance for reducing dietary sodium, the overabundance of sodium in the food supply makes it an uphill struggle. According to Altman, “Sodium reduction is difficult to achieve because of limited choices of low-sodium options. Mandating a lower sodium content is likely to have more impact than simply asking individuals to reduce their own intake.”
It’s been estimated that a 40% reduction in the American intake of sodium over 10 years could save at least 280,000 lives in the United States alone and drastically decrease the number of years of living with a disability as the result of high blood pressure.12 Despite ongoing public health education and policy initiatives, the majority of the US population exceeds current recommendations for sodium intake.13 Among adults with hypertension, 86% exceed the National Academy of Sciences recommendation of 2,300 mg dietary sodium per day.13,14 The WHO report recommends adults consume less than 2,000 mg per day. The American Heart Association (AHA) says that ideally, sodium intake should be even lower, to no more than 1,500 mg per day.15 Yet, the average American intake of sodium is 3,400 mg per day, with some individuals consuming much more.
The AHA says that reducing intake by 1,000 mg per day can improve blood pressure and heart health. However, much of the food supply, especially fast food, and some frozen preprepared meals, have far more than 3,400 mg in a single serving. For example, some fast-food french fries can contain as much as 1,480 mg per serving, close to the ideal amount of sodium the AHA recommends for one day. Fast-food breakfast meals can provide more than 2,000 mg of sodium, and some restaurant meals can contain almost 8,000 mg—31/2 times the recommended intake.
“Mandatory sodium reduction targets for packaged and restaurant foods would be the most effective strategy to reduce sodium content for packaged and prepared foods, as compared with voluntary targets,” Arcand says. Several policy and education initiatives aimed at lowering sodium intakes have been implemented for decades but with little effect on the average sodium intake. The Journal of the American College of Cardiology published a state-of-the-art review in 2020 that also concluded that salt reduction is the most cost-effective, feasible, and affordable strategy to prevent CVD.16
“Unfortunately, when I worked in the cardiovascular ICU, there were rarely empty beds,” says Jessica Sylvester, MS, RD, LDN, founder of FL Nutrition Group, LLC, and a spokesperson for the Academy of Nutrition and Dietetics. “Our current food landscape makes it so that ‘eating healthfully’ is a constant, moment-by-moment, intentional consumer choice. It can be exhausting, especially if consumers don’t know which diet best meets their needs and goals.”
The WHO report recommends several sodium-reduction policies as practical actions that the organization says should be undertaken immediately to prevent CVD and its associated costs. These include lowering sodium content in food products, implementing front-of-pack labeling to help consumers select foods with lower sodium content, and conducting mass media campaigns to alter consumer behavior around sodium.
While the WHO report advocates front-of-label sodium information, Lackland says, “Labels can be helpful, but they can also be confusing. Salt content is typically described by serving size, which varies greatly from person to person.”
Cutting back on sodium intake may be one of the more difficult dietary changes to make, but Antman says, “Every little bit helps. However, in some patients, even a substantial reduction in sodium intake may not be sufficient if they have had hypertension for a long time. Drugs may still be required to lower their blood pressure, but hopefully fewer drugs and lower doses may be needed if they make the necessary lifestyle changes.”
Salt Substitutes
Salt substitutes (low-sodium or sodium-free salts), such as Morton Salt Substitute, MySALT, Nu-Salt, and No Salt, provide nonpharmaceutical ways to reduce dietary sodium and improve hypertension control. Most low-sodium salt substitutes (LSSS) are sodium-free and instead provide flavor with potassium chloride. A 1/4 tsp serving of a sodium-free, potassium chloride salt substitute contains about 800 mg of potassium.17 However, some salt substitute brands, such as Morton Lite-Salt and Low Salt, substitute only part of the sodium chloride with potassium chloride and provide anywhere from 170 mg to 290 mg sodium per 1/4 tsp.
Not only can salt substitutes help reduce sodium intake but also a higher potassium intake has been shown to have an inverse association with blood pressure by counteracting sodium’s effects. But potassium intakes in the United States generally are lower than recommended. Because potassium is underconsumed by most people in the United States, it was identified in the 2020–2025 Dietary Guidelines for Americans as a nutrient of concern.18 However, some people find potassium-containing salt substitutes bitter or metallic tasting.17 Potassium-enriched LSSS are most likely to be accepted when they contain no more than 30% potassium chloride.19
The Salt Substitute and Stroke Study, an open-label, randomized clinical trial in China recruited 21,000 subjects who had a history of stroke or were aged 60 or older and had high blood pressure. Researchers replaced the subjects’ salt intake with a salt substitute (75% sodium chloride, 25% potassium chloride). They were followed for almost five years, during which there were significantly lower rates of stroke, major adverse cardiovascular events, and death from all causes compared with those who received regular salt.20 No adverse effects, including hyperkalemia (high serum potassium levels), were observed.
While there’s evidence that using salt substitutes containing potassium chloride can aid in lowering blood pressure, there’s a concern that hyperkalemia may be a risk for some subgroups in the population. Hyperkalemia increases the risk of arrhythmias and sudden cardiac death. A report published in the journal Hypertension in 2020 concluded that there was insufficient evidence regarding the effects of potassium-enriched salt substitutes on hyperkalemia. The authors called for additional research.18
However, those specifically at risk of hyperkalemia are patients with chronic kidney disease, diabetes, severe heart failure, of older age, individuals with adrenal insufficiency, and those taking medications that impair potassium excretion, such as angiotensin-converting enzyme inhibitors, angiotensin-II receptor blockers, direct renin inhibitors, nonsteroidal anti-inflammatory drugs, calcineurin inhibitors, heparin and derivatives, aldosterone antagonists, and potassium-sparing diuretics.21 However, most reported cases of life-threatening hyperkalemia due to salt substitute use involved individuals with more than one risk factor.18 Still, potassium-containing salt substitutes aren’t recommended for patients who have any of these health conditions or take these medications.
Of course, natural flavorings from herbs and spices such as basil, cayenne pepper, celery seed, garlic, and thyme often can provide a rich flavor substitute for salt and salt substitutes.
Bottom Line
“The WHO statistics should be a call to action to redouble our efforts to systematically decrease the intake of sodium on a global basis,” Antman says. “The entrenched patterns of high sodium intake are fueled by habits and by the publication of studies with significant limitations, but that question the need to lower sodium intake.”
“To say that reducing sodium intake will be a panacea for cardiovascular events is inappropriate,” Sylvester says. Moreover, it’s not a one-diet-prescription fits all. She emphasizes that dietary interventions should always be patient and condition specific. The successful solution to lowering sodium intake will require changes in the food supply and educated consumers making smarter sodium choices.
— Densie Webb, PhD, RD, is a freelance writer, editor, and industry consultant based in Austin, Texas.
References
1. World Health Organization. WHO global report on sodium intake reduction. https://apps.who.int/iris/bitstream/handle/10665/366393/9789240069985-eng.pdf?sequence=1&isAllowed=y. Published 2023.
2. Wallace T, Cowan A, Bailey R. Current sodium intakes in the United States and the modeled effects of glutamate incorporation into select savory products. Nutrients. 2019;11:2691.
3. Tsai Y-C, Tsao Y-P, Huang C-J, et al. Effectiveness of salt substitute on cardiovascular outcomes: a systematic review and meta-analysis. J Clin Hypertens (Greenwich). 2022;24(9):1147-1160.
4. Patel Y, Joseph J. Sodium intake and heart failure. Int J Mol Sci. 2020;21(24): 9474.
5. Zhao D, Li HM, Li CX, Zhour B. 24-hour urinary sodium excretion association with cardiovascular events: a systematic review and dose-response meta-analysis. Biomed Environ Sci. 2022;35:921-930.
6. D’Elia L, Galletti F, Strazzullo P. Dietary salt intake and risk of gastric cancer. Cancer Treat Res. 2014;159:83-95.
7. Wu X, Chen L, Cheng J, Qian J, Fang Z, Wu J. Effect of dietary salt intake on risk of gastric cancer: a systematic review and meta-analysis of case-control studies. Nutrients. 2022;14(20):4260.
8. Moosavian SP, Haghighatdoost F, Surkan PJ, Azadbakht L. Salt and obesity: a systematic review and meta-analysis of observational studies. Int J Food Sci Nutr. 2017;68(3):26577.
9. Hussain K, Murdin L, Schilder AG. Restriction of salt, caffeine and alcohol intake for the treatment of Ménière’s disease or syndrome. Cochrane Database Syst Rev. 2018;(12):CD012173
10. Teucher B, Dainty JR, Spinks CA, et al. Sodium and bone health: impact of moderately high and low salt intakes on calcium metabolism in postmenopausal women. J Bone Miner Res. 2008;23(9):1477-1485.
11. Brown R. Low dietary sodium potentially mediates COVID-19 prevention associated with whole-food plant-based diets. Br J Nutr. 2022;129:1-6.
12. Brand A, Visser ME, Schoonees A, Naude CE. Replacing salt with low-sodium salt substitutes (LSSS) for cardiovascular health in adults, children and pregnant women. Cochrane Database Syst Rev. 2022;8:CD015207.
13. Orla M, Harrison M, Stallings VA, eds. National Academies of Sciences, Engineering, and Medicine, Health and Medicine Division, Food and Nutrition Board, Committee to Review the Dietary Reference Intakes for Sodium and Potassium. Dietary reference intakes for sodium and potassium. Washington, D.C.: National Academies Press; 2019.
14. Chen X, Du J, Wu X, Cao W, Sun S. Global burden attributable to high sodium intake from 1990 to 2019. Nutri Metab Cardiovasc Dis. 2021;31:3314-3321.
15. American Heart Association. Why should I limit sodium intake? https://www.heart.org/-/media/files/health-topics/answers-by-heart/why-should-i-limit-sodium.pdf. Published 2021. Accessed April 11, 2023.
16. He FJ, Tan M, Ma Y, MacGregor G. Salt reduction to prevent hypertension and cardiovascular disease. J Am Coll Cardiol. 2020; 75:632-647.
17. Can a salt substitute cause high potassium levels? Harvard Health Publishing website. https://www.health.harvard.edu/heart-health/can-a-salt-substitute-cause-high-potassium-levels#:~:text=A%20quarter%2Dteaspoon%20serving%20of,potassium%2C%20which%20is%204%2C700%20mg. Published December 1, 2019. Accessed April 15, 2023.
18. Hoy MK, Goldman JD, Moshfegh AJ. Potassium intake of the U.S. population: what we eat in America, NHANES 2017–2018. Food Surveys Research Group Dietary Data Brief No. 47.
19. Greer R, Marklund M, Anderson C, Cobb L, Dalcin A, et al. Potassium-enriched salt substitutes as a means to lower blood pressure. Benefits and Risks. Hypertension. 2020;75:266-2274.
20. Neal B, Wu Y, Feng X, et al. Effect of salt substitution on cardiovascular events and death. N Eng J Med. 2021;385(12):1067-1077.
21. Ben Salem C, Badreddine A, Fathallah N, Slim R, Hmouda H. Drug-induced hyperkalemia. Drug Saf. 2014;37(9):677-692.