Evidence on Effects of Salt Reduction Calls for a Redesign of Salt Dietary Guidelines

Your Body May Need More Salt

Most people need more sodium than they think, especially if they’re active. In fact, low sodium is the most common type of electrolyte imbalance.

Sodium is an essential nutrient and if you don’t get enough, you risk a range of unwanted symptoms and health issues, including raised blood pressure, muscle cramps, insomnia, raised cholesterol, increased stress response, fatigue and osteoporosis.7, 8, 9, 10, 11

The problem is, for many years we have been told to limit our salt consumption to 2,000 mg of sodium per day (equivalent to about 5,000 mg or 5 g of salt or 1 teaspoon). This recommendation is largely based on short-term observational studies linking higher sodium intakes to higher blood pressure. There is, however, very limited evidence available to support these recommendations.12

There is also a growing body of research bringing these recommendations into question.

In 1988, the Intersalt Study looked at sodium intake and blood pressure in over 10,000 people across 52 regions of the world. In most populations, the researchers found no link between sodium intake and high blood pressure. In fact, the population that ate the most salt, about 14 grams a day, had a lower median blood pressure than the population that ate the least, about 7.2 grams a day.13

Then, in 2017, the Framingham Offspring Study analysed 2,632 people with normal blood pressure. Researchers split these people into two groups, high sodium consumers (>2.5g) and low sodium consumers (<2.5g). Surprisingly, the high sodium group had lower blood pressure than the low sodium group.

The researchers went on to say that there is no scientific support for lowering sodium intakes among healthy adults to below 2.3 g/day (US guidelines) as recommended.

What this study did identify is the need to consider the intakes of other minerals such as potassium, magnesium, and calcium in addition to sodium in relation to blood pressure regulation.14

In 2020, a Cochrane Collaboration Review (a review of all the available evidence) found that the numerous adverse side effects of salt restriction were more consistent than the effects on blood pressure.15

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 health risks. The current recommendation for sodium corresponds with a higher risk of adverse health outcomes.16

Sodium Intake and Health: What Should We Recommend Based on the Current Evidence? Nutrients 2021

Evidence on Effects of Salt Reduction Calls for a Redesign of Salt Dietary Guidelines

One hundred and ninety‐five intervention studies of 12,296 individuals and an analysis of an additional 131 studies were included in this Cochrane Review examining the effect of reduced salt intake on blood pressure and potential side effects of salt reduction on some hormones and lipids.

This study found that neither the supporting studies selected by the health institutions nor randomised controlled trials and prospective observational studies document that a salt intake below 5.8 g (2.3 g of sodium) has beneficial health effects.

The researchers went on to say that, although there is an association between salt intake and blood pressure, both in randomised controlled trials and in observational studies, this association is weak, especially in non-obese individuals with normal blood pressure.

They further concluded that a salt intake below 5.8 g is associated with the activation of the renin-angiotensin-aldosterone system (the system of hormones and proteins that regulate your blood pressure), an increase in plasma lipids and increased mortality. The effects of sodium reduction on potential side effects (hormones and lipids) were more consistent than the effect on blood pressure, especially in people with normal blood pressure.

Graudal NA, Hubeck-Graudal T, Jurgens G. Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterol, and triglyceride. Cochrane Database of Systematic Reviews 2020, Issue 12. Art. No.: CD004022. DOI: 10.1002/14651858.CD004022.pub5. Accessed 24 July 2023.

Low Sodium Intakes are Not Associated with Lower Blood Pressure Levels

Researchers used data from 2,632 subjects with normal blood pressure, aged 30–64 years, in the Framingham Offspring Study.

Detailed dietary records were collected and used to address the question of the long-term effect of dietary sodium in particular on systolic and diastolic blood pressures over 16 years of follow-up.

While the researchers expected dietary sodium intake to be positively associated with both systolic and diastolic blood pressure, the opposite was found.

Dietary potassium, as expected, was inversely associated with systolic and diastolic blood pressure.

Results for magnesium and calcium were very similar to those for potassium.

It was concluded that these long-term data from the Framingham Study provide no support for lowering sodium intakes among healthy adults to below 2.3 g/day as recommended. This study does support the finding of a clear inverse association between potassium, magnesium, and calcium and blood pressure change over time.

Moore, L.L., Singer, M.R. and Bradlee, M.L. (2017), Low Sodium Intakes are Not Associated with Lower Blood Pressure Levels among Framingham Offspring Study Adults. The FASEB Journal, 31: 446.6  

Those Who Consume 3 g to 6 g of Salt Have the Lowest Risk of Death and Cardiovascular Events

The PURE (Prospective Urban Rural Epidemiology) study was a large, international prospective analysis examining the impact of societal influences on chronic diseases. Over 100,000 people in low-, middle, and high-income countries were studied.

The researchers examined the association between estimated urinary sodium and potassium excretion and the outcome of death and major cardiovascular events.

The study found that a sodium intake between 3 g per day and 6 g per day was associated with a lower risk of death and cardiovascular events than either a higher or lower estimated level of intake.

Current guidelines, which recommend a maximum sodium intake of 1.5 to 2.4 g per day, are based on evidence from largely short-term clinical trials showing that reducing sodium intake from a moderate to a low level results in modest reductions in blood pressure.

by Danny Urbinder

Intersalt: an international study of electrolyte excretion and blood pressure. Results for 24 hour urinary sodium and potassium excretion. Intersalt Cooperative Research Group. British Medical Journal 1988; 297 :319 doi:10.1136/bmj.297.6644.319

References:

  1. Ahmed M. El-Sharkawy and others, Acute and chronic effects of hydration status on health, Nutrition Reviews, Volume 73, Issue suppl_2, 1 September 2015, Pages 97–109, https://doi.org/10.1093/nutrit/nuv038
  2. Hamouti N, Fernández-Elías VE, Ortega JF, Mora-Rodriguez R. Ingestion of sodium plus water improves cardiovascular function and performance during dehydrating cycling in the heat. Scand J Med Sci Sports. 2014 Jun;24(3):507-18. doi: 10.1111/sms.12028. Epub 2012 Dec 17. PMID: 23253191.
  3. Pre-exercise sodium loading aids fluid balance and endurance for women exercising in the heat, Stacy T. Sims, Nancy J. Rehrer, Melanie L. Bell, and James D. Cotter, Journal of AppliedPhysiology 2007 103:2, 534-541
  4. Shrimanker I, Bhattarai S. Electrolytes. 2023 Apr 23. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–. PMID: 31082167.
  5. Choi D-H, Cho J-Y, Koo J-H, Kim T-K. Effects of Electrolyte Supplements on Body Water Homeostasis and Exercise Performance during Exhaustive Exercise. Applied Sciences. 2021; 11(19):9093. https://doi.org/10.3390/app11199093
  6. Lau WY, Kato H, Nosaka K. Effect of oral rehydration solution versus spring water intake during exercise in the heat on muscle cramp susceptibility of young men. J Int Soc Sports Nutr. 2021 Mar 15;18(1):22. doi: 10.1186/s12970-021-00414-8. PMID: 33722257; PMCID: PMC7962362.
  7. Fujisawa, C., Umegaki, H., Sugimoto, T. et al.Mild hyponatremia is associated with low skeletal muscle mass, physical function impairment, and depressive mood in the elderly. BMC Geriatr 21, 15 (2021). https://doi.org/10.1186/s12877-020-01955-4
  8. Wang J, Deng Y, Zou X, Luo H, Jose PA, Fu C, Yang J, Zeng C. Long-term low salt diet increases blood pressure by activation of the renin-angiotensin and sympathetic nervous systems. Clin Exp Hypertens. 2019;41(8):739-746. doi: 10.1080/10641963.2018.1545850. Epub 2018 Nov 18. PMID: 30451012; PMCID: PMC6525650.
  9. Fabrice Gankam Kengne, Guy Decaux, Hyponatremia and the Brain, Kidney International Reports, Volume 3, Issue 1, 2018, Pages 24-35, ISSN 2468-0249, https://doi.org/10.1016/j.ekir.2017.08.015.
  10. Pati P, Fulton DJ, Bagi Z, Chen F, Wang Y, Kitchens J, Cassis LA, Stepp DW, Rudic RD. Low-Salt Diet and Circadian Dysfunction Synergize to Induce Angiotensin II-Dependent Hypertension in Mice. Hypertension. 2016 Mar;67(3):661-8. doi: 10.1161/HYPERTENSIONAHA.115.06194. Epub 2016 Jan 18. PMID: 26781276; PMCID: PMC4752410.
  11. Vitiello MV, Prinz PN, Halter JB. Sodium-restricted diet increases nighttime plasma norepinephrine and impairs sleep patterns in man. J Clin Endocrinol Metab. 1983 Mar;56(3):553-6. doi: 10.1210/jcem-56-3-553. PMID: 6822653.
  12. Martin O’Donnell and others, Salt and cardiovascular disease: insufficient evidence to recommend low sodium intake, European Heart Journal, Volume 41, Issue 35, 14 September 2020, Pages 3363–3373, https://doi.org/10.1093/eurheartj/ehaa586
  13. Intersalt: an international study of electrolyte excretion and blood pressure. Results for 24 hour urinary sodium and potassium excretion. Intersalt Cooperative Research Group. British Medical Journal 1988; 297 :319 doi:10.1136/bmj.297.6644.319
  14. Moore, L.L., Singer, M.R. and Bradlee, M.L. (2017), Low Sodium Intakes are Not Associated with Lower Blood Pressure Levels among Framingham Offspring Study Adults. The FASEB Journal, 31: 446.6-446.6. https://doi.org/10.1096/fasebj.31.1_supplement.446.6
  15. Graudal NA, Hubeck-Graudal T, Jurgens G. Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterol, and triglyceride. Cochrane Database of Systematic Reviews 2020, Issue 12. Art. No.: CD004022. DOI: 10.1002/14651858.CD004022.pub5. Accessed 24 July 2023.
  16. Mente A, O’Donnell M, Yusuf S. Sodium Intake and Health: What Should We Recommend Based on the Current Evidence? Nutrients. 2021; 13(9):3232. https://doi.org/10.3390/nu13093232
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