During my time in undergrad, sodium was constantly being demonized. I’ve heard people dismiss foods as being “unhealthy” simply because of their sodium content. So much so, that in a class discussion on eating out (I believe the specific eatery in question was Olive Garden), the gasp of the conversation revolved around the sodium content of a menu item, rather than the low nutrient density and boatload of calories it offered.
The 2015-2020 Dietary Guidelines for Americans recommend that Americans consume less than 2,300 mg/d of sodium as part of a healthy eating pattern (1). I can count on one hand the number of people I know who eat less than 2,300 mg of sodium per day and that number is zero, which isn’t very surprising. It has been documented that human sodium intake tends to range from about 2,622-4,830 mg/d (2), with Americans eating about 3,400 to 3,800 mg/d (3).
In order for the average American to limit their sodium consumption to 2,300 mg/d, substantial dietary adjustments would have to take place. The question is: is it worth it for healthy people to take on this challenge? For hypertensive individuals, it’s been proven time and time again that sodium reduction works. The primary dietary strategy to counter hypertension is the Dietary Approaches to Stop Hypertension or DASH diet. The DASH diet emphasizes fruits, vegetables, fat-free/low-fat dairy, whole grains, nuts and legumes, and limits saturated fat, cholesterol, red and processed meats, sweets, added sugars, sodium (1500-2,300 mg/d), and sugar-sweetened beverages. It has been consistently shown to reduce blood pressure and is associated with a decreased incidence of cardiovascular disease (4). If you are hypertensive, it’s a no brainer to reduce your sodium intake, but for normotensive individuals, the decision isn’t so clear.
What the Data Says
On April 26th, 2019, a review titled “Dose-response relation between dietary sodium and blood pressure: a meta-regression analysis of 133 randomized controlled trials,” was published in The American Journal of Clinical Nutrition (5). The analysis was based on the 75th blood pressure percentile of the US population (131/79 mm Hg), which is considered “elevated” (6).
The results showed that in individuals with a mean systolic blood pressure above 131 mm Hg and a mean diastolic blood pressure above 78 mm Hg (hypertensive individuals), a reduction in mean sodium intake of 2,300 mg/d resulted in significant decreases in blood pressure of -7.7 mm Hg and -3.0 mm Hg, respectively. On the other hand, in more or less normotensive individuals, or those with a mean systolic blood pressure </= 131 mm Hg and a mean diastolic blood pressure </= 78 mm Hg, a reduction in mean sodium intake of 2,300 mg/d was associated with a mean decrease of only -1.46 mm Hg and -0.07 mm Hg, respectively. The authors concluded that only study groups with blood pressures in the highest 25th percentile of the population showed a clinically significant drop in blood pressure with sodium restriction.
Another systematic review titled “Effect of longer-term modest salt reduction on blood pressure.,” analyzed data from 3,230 participants (7). In hypertensive individuals, median blood pressure on a usual sodium intake of ~3,700 mg/d was 148/93 mm Hg. For this group, a reduction of ~1,700 mg of sodium per day resulted in pooled estimate changes of -5.39 mm Hg for systolic blood pressure and -2.82 mm Hg for diastolic blood pressure. In the normotensive group, median blood pressure on a usual sodium intake of ~3,500 mg/d was 127/77 mm Hg. In this group, a reduction of ~1,700 mg of sodium per day resulted in pooled estimate changes of -2.42 mm Hg for systolic blood pressure and -1.00 mm Hg for diastolic blood pressure. While changes did occur in both groups, the results fall in line with other research exhibiting a lackluster effect of sodium restriction on blood pressure in normotensive subjects.
A third analysis titled “Effect of lower sodium intake on health: systematic review and meta-analyses,” found similar results, noting a relatively small effect of decreased sodium intake on blood pressure in people without high blood pressure (8). Aburto and colleagues reported that sodium reduction in hypertensive subjects decreased systolic blood pressure by 4.06 mm Hg on average, while normotensive subjects only experienced an average decrease of 1.38 mm Hg.
Lastly, in a major review paper titled “Associations of urinary sodium excretion with cardiovascular events in individuals with and without hypertension: a pooled analysis of data from four studies,” 133,118 individuals were studied. The population was about 50/50 hypertensive/normotensive. In this analysis, 24-hour urinary excretion of sodium and potassium were used as surrogates for daily sodium and potassium intake. The primary outcome being studied was defined as the composite of death, myocardial infarction, stroke, and heart failure.
The results displayed that in individuals without hypertension, compared with 4,000-5,000 mg/d, sodium excretion of 7,000 mg/d or more was not associated with risk of the primary composite outcome, but excretion of less than 3,000 mg/d was associated with an increased risk. In comparison, In individuals with hypertension, sodium excretion of 7,000 mg/d or more and less than 3,000 mg/d were both associated with increased risk of the composite outcome.
This suggests a U-shaped association between sodium excretion and cardiovascular events and mortality. Meaning, if you eat too little or too much sodium, negative consequences may transpire. This makes sense as it applies to just about everything else we consume (you can die from drinking too much water). Previous studies have looked at this phenomenon and have reported similar findings, suggesting that sodium intakes below 2,500 mg/d and above 5,000 mg/d may be equally harmful in certain populations (9,10).
Overall, the data tends to suggest an insignificant to at best very modest effect of reducing sodium intake on health parameters in normotensive individuals.
Other Things to Consider
It is important to note that research is based on averages, and while you’re probably not as special of a snowflake as you may think you are, you are not an average. It has been known for decades that some people are more sensitive to sodium intake than others (11). Though the exact definition is debated, salt-resistant individuals can eat high amounts of salt with little to no effect on their blood pressure. Whereas those who are salt-sensitive will react with a significant rise in blood pressure as a consequence of a high salt diet. Salt sensitivity is observed in both hypertensive and normotensive subjects. It appears to be a predictor of the likelihood to develop hypertension over time and a predictor of higher cardiovascular morbidity and mortality (12). It is estimated that about 50-60% of hypertensives are salt sensitive and this condition is increased in aging, in African-Americans, and in persons with metabolic syndrome or obesity (13).
In a 15-year follow-up study of normotensive individuals, it was found that a high salt sensitivity at baseline was a significant independent predictor of hypertension down the road (14). Even if you are currently normotensive, it is important to keep tabs on your blood pressure and even potentially be evaluated for salt sensitivity, as it is likely a benefit for this population to be more conservative with their sodium intake, considering they are more likely to develop hypertension.
Another important variable to consider is potassium intake. Potassium supplementation has been shown to effectively reduce systolic and diastolic blood pressure in hypertensive individuals (15), especially when sodium intake is above 4,000 mg/d (16). In terms of solely increasing potassium intake from whole food sources, there is a lack of direct evidence showing it has a beneficial effect on blood pressure (17), but an abundance of epidemiological research has long suggested a protective effect of high potassium intake against the genesis of hypertension (18). And there is strong rationale as to why increasing potassium intake would have a beneficial effect on blood pressure as potassium increases urinary sodium excretion, diminishing body sodium levels. In addition, the most abundant food sources of potassium are fruits and vegetables and it’s pretty much always a good idea to increase your intake of these.
It is not only important to consider how much sodium you are consuming, but the ratio of sodium to potassium when striving for healthy blood pressure. The data tends to suggest that a high sodium to potassium ratio (high sodium intake and low potassium intake) increases the risk for hypertension (19). It also shows that a low sodium intake combined with a high potassium intake is a fantastic recipe to counter hypertension as evidenced by the success of the DASH diet and other research (20). In all, there is even less reason for a normotensive individual to be concerned with a habitual sodium intake above 2,300 mg/d if it is coupled with high potassium intake.
Lastly, athletes should especially not be concerned with restricting their sodium intake. Sodium is the primary electrolyte lost in sweat. About 1,000 mg of sodium is lost per liter of sweat (20) and it has been reported that American Football players average ~2.0 L/h of sweat (21). Similar circumstances have been documented in other athletes, including elite soccer players who lost 2,260 +/- 560 mg of sodium in a 90-minute training session (22). This is crucial information because excessive sodium losses can lead to muscle cramps, ultimately hindering performance. In an interesting case study on a nationally ranked tennis player, the athlete had to increase sodium intake from <3,900 mg per day to 5,800-7,800 mg/d in order to effectively eliminate heat cramps (23). Unless medical history and physical exams dictate otherwise, it is likely not an ideal strategy to limit sodium consumption if you are an athlete or very physically active.
So, if you’re an otherwise healthy, normotensive individual, without a family history of hypertension, is it worth revamping your diet in order to adhere to the Dietary Guideline’s recommendation to not exceed 2,300 mg/d of sodium? Probably not. The data seems to support an acceptable range of 2,500 – 5,000 mg/d of sodium, which is what most people tend to eat per day anyway.
- CDC – Salt Home – DHDSP. Centers for Disease Control and Prevention. https://www.cdc.gov/salt/index.htm. Accessed June 20, 2019.
- McCarron DA, Kazaks AG, Geerling JC, Stern JS, Graudal NA. Normal range of human dietary sodium intake: a perspective based on 24-hour urinary sodium excretion worldwide. American journal of hypertension. https://www.ncbi.nlm.nih.gov/pubmed/23978452. Published October 2013. Accessed June 20, 2019.
- Powles J, Fahimi S, Micha R, et al. Global, regional and national sodium intakes in 1990 and 2010: a systematic analysis of 24 h urinary sodium excretion and dietary surveys worldwide. BMJ open. https://www.ncbi.nlm.nih.gov/pubmed/24366578. Published December 20, 2013. Accessed June 20, 2019.
- Chiavaroli L, Viguiliouk E, Nishi SK, et al. DASH Dietary Pattern and Cardiometabolic Outcomes: An Umbrella Review of Systematic Reviews and Meta-Analyses. Nutrients. https://www.ncbi.nlm.nih.gov/pubmed/30764511. Published February 5, 2019. Accessed June 20, 2019.
- Graudal, Taylor, S R. Dose-response relation between dietary sodium and blood pressure: a meta-regression analysis of 133 randomized controlled trials. OUP Academic. https://academic.oup.com/ajcn/article-abstract/109/5/1273/5480600. Published April 26, 2019. Accessed June 20, 2019.
- Understanding Blood Pressure Readings. www.heart.org. https://www.heart.org/en/health-topics/high-blood-pressure/understanding-blood-pressure-readings. Accessed June 20, 2019.
- He FJ, Li J, Macgregor GA. Effect of longer-term modest salt reduction on blood pressure. The Cochrane database of systematic reviews. https://www.ncbi.nlm.nih.gov/pubmed/23633321. Published April 30, 2013. Accessed June 20, 2019.
- 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 (Clinical research ed.). https://www.ncbi.nlm.nih.gov/pubmed/23558163. Published April 4, 2013. Accessed June 20, 2019.
- Alderman, H. M, Cohen, W. H. Dietary Sodium Intake and Cardiovascular Mortality: Controversy Resolved? OUP Academic. https://academic.oup.com/ajh/article/25/7/727/161818. Published July 1, 2012. Accessed June 20, 2019.
- Graudal N, Jürgens G, Baslund B, Alderman MH. Compared with usual sodium intake, low- and excessive-sodium diets are associated with increased mortality: a meta-analysis. American journal of hypertension. https://www.ncbi.nlm.nih.gov/pubmed/24651634. Published September 2014. Accessed June 20, 2019.
- Luft FC, Weinberger MH. Heterogeneous responses to changes in dietary salt intake: the salt-sensitivity paradigm. The American journal of clinical nutrition. https://www.ncbi.nlm.nih.gov/pubmed/9022556. Published February 1997. Accessed June 20, 2019.
- Galletti F, Strazzullo P. The blood pressure-salt sensitivity paradigm: pathophysiologically sound yet of no practical value. Nephrology, dialysis, transplantation: official publication of the European Dialysis and Transplant Association – European Renal Association. https://www.ncbi.nlm.nih.gov/pubmed/27521374. Published September 2016. Accessed June 20, 2019.
- Rust P, Ekmekcioglu C. Impact of Salt Intake on the Pathogenesis and Treatment of Hypertension. Advances in experimental medicine and biology. https://www.ncbi.nlm.nih.gov/pubmed/27757935. Published 2017. Accessed June 20, 2019.
- Barba G, Galletti F, Cappuccio FP, et al. Incidence of hypertension in individuals with different blood pressure salt-sensitivity: results of a 15-year follow-up study. Journal of hypertension. https://www.ncbi.nlm.nih.gov/pubmed/17563570. Published July 2007. Accessed June 20, 2019.
- Adrogué HJ, Madias NE. The impact of sodium and potassium on hypertension risk. Seminars in nephrology. https://www.ncbi.nlm.nih.gov/pubmed/25016398. Published May 2014. Accessed June 20, 2019.
- Aburto NJ, Hanson S, Gutierrez H, Hooper L, Elliott P, Cappuccio FP. Effect of increased potassium intake on cardiovascular risk factors and disease: systematic review and meta-analyses. BMJ (Clinical research ed.). https://www.ncbi.nlm.nih.gov/pubmed/23558164. Published April 4, 2013. Accessed June 20, 2019.
- Stone MS, Martyn L, Weaver CM. Potassium Intake, Bioavailability, Hypertension, and Glucose Control. Nutrients. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4963920/. Published July 22, 2016. Accessed June 20, 2019.
- Krishna GG. Effect of potassium intake on blood pressure. American Society of Nephrology. https://jasn.asnjournals.org/content/1/1/43.long. Published July 1, 1990. Accessed June 20, 2019.
- Perez V, Chang ET. Sodium-to-potassium ratio and blood pressure, hypertension, and related factors. Advances in nutrition (Bethesda, Md.). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4224208/. Published November 3, 2014. Accessed June 20, 2019.
- Karpinski C, Rosenbloom C. Sports Nutrition: a Handbook for Professionals. Chicago: Academy of Nutrition and Dietetics; 2017.
- Davis JK, Baker LB, Barnes K, Ungaro C, Stofan J. Thermoregulation, Fluid Balance, and Sweat Losses in American Football Players. Sports medicine (Auckland, N.Z.). https://www.ncbi.nlm.nih.gov/pubmed/27071988. Published October 2016. Accessed June 20, 2019.
- Maughan RJ, Merson SJ, Broad NP, Shirreffs SM. Fluid and electrolyte intake and loss in elite soccer players during training. International journal of sport nutrition and exercise metabolism. https://www.ncbi.nlm.nih.gov/pubmed/15256693. Published June 2004. Accessed June 20, 2019.
- Bergeron MF. Heat cramps during tennis: a case report. International journal of sport nutrition. https://www.ncbi.nlm.nih.gov/pubmed/8653105. Published March 1996. Accessed June 20, 2019.