Clinical trial data on decreasing Na and/or increasing K consumption on CV outcomes
Building on the cohort studies reporting that diets high in sodium and low in potassium are associated with hypertension and cardiovascular disease, clinical trials report that decreasing dietary sodium intake reduces BP and the risk of a cardiovascular event. For example, in a meta-analysis of 85 clinical trials studying the link between sodium and BP, the investigators concluded that there was a linear relationship between sodium intake and BP, with larger reductions in sodium intake associated with greater reductions in BP, down to a daily sodium intake of 1,000 to 1,500 mg.9 The effect of sodium reduction on BP was greatest in study participants with higher BP at baseline.
In a cluster-randomized clinical trial in China, people living in 600 villages were assigned to a control group, continuing to use sodium chloride in their food preparation or an experimental intervention, replacing sodium chloride with a substitute product containing 75% sodium chloride and 25% potassium chloride by weight.10 The inclusion criteria included people ≥60 years of age with high BP or a history of stroke. The mean duration of follow-up was 4.7 years. Half of the participants were female. A total of 73% of the participants had a history of stroke and 88% had hypertension. In this study, the rate of death was lower in the group that used the salt substitute than in the group using sodium chloride (39 vs 45 deaths per 1,000 person-years; rate ratio (RR) 0.88; 95% CI, 0.82–0.95, P<.001). The rate of major cardiovascular events (nonfatal stroke, nonfatal acute coronary syndrome or death from vascular causes) was decreased in the group that used salt substitute compared with the group using sodium chloride (49 vs 56 events per 1,000 person-years, rate ratio (RR), 0.87; 95% CI, 0.80–0.94; P<.001). Similarly, the rate of stroke was decreased in the group that used salt substitute compared with the group using sodium chloride (29 vs 34 events per 1,000 person-years; rate ratio (RR), 0.86; 95% CI, 0.77–0.96; P = .006). This study shows that by decreasing sodium intake and increasing potassium, cardiovascular outcomes are improved in people at high risk for a cardiovascular event.10 People with kidney disease or taking medications that decrease renal excretion of potassium should consult with their health care provider before using potassium chloride containing salt substitutes.
What is your daily intake of sodium and potassium?
Almost all packaged prepared foods have labels indicating the amount of sodium in one serving. Many packaged foods also report the amount of potassium in one serving. Many processed foods contain high amounts of sodium and low amounts of potassium. Processed and ultra-processed foods are a major dietary source of sodium.11 In contrast to processed foods, fresh fruits, vegetables, and milk have high quantities of potassium and low amounts of sodium. As an example, a major brand of canned chicken broth has 750 mg of sodium and 40 mg of potassium per one-half cup, a ratio of sodium to potassium of 19:1. By contrast, canned red kidney beans have 135 mg of sodium and 425 mg of potassium in one-half cup, a ratio of sodium to potassium of 1:3. Patients can better understand their daily sodium and potassium intake by reading the food labels. Calculating a sodium to potassium ratio for a food may help people better understand their salt intake and identify foods associated with positive health outcomes.
The optimal target for daily consumption of sodium and potassium is controversial (TABLE 2). The mean daily intakes of sodium and potassium in the United States are approximately 3,380 mg and 2,499 mg,respectively.12 The American College of Cardiology (ACC) recommends that an optimal diet contains <1,500 mg/d of sodium, a stringent target.1 If that target is unattainable, people should at least aim for a 1,000 mg/d-reduction in their current sodium intake.1 The World Health Organization strongly recommends that adults consume <2,000 mg/d of sodium.13 The National Academy of Science recommends adults seeking to reduce the risk of cardiovascular disease consume <2,300 mg/d of sodium.14 The top dietary sources of sodium include deli meat, pizza, burritos and tacos, soups, savory snacks (chips, crackers, popcorn), fried poultry, burgers, and eggs.15
The optimal target for daily consumption of potassium is controversial. The ACC recommends that an optimal diet contains 3,500–5,000 mg/d of potassium.1 The World Health Organization recommends that adults consume >3,510 mg/d of potassium.16 The top dietary sources of potassium include milk, fruit, vegetables, coffee, savory snacks (chips, crackers, popcorn), fruit juice, white potatoes, deli meats, burritos, and tacos.15 The foods with the greatest amount of potassium include banana, avocado, acorn squash, spinach, sweet potatoes, salmon, apricots, grapefruit, broccoli, and white beans. People with kidney disease or those who are taking medications that interfere with renal excretion of potassium should consult with their health care provider before adding more potassium to their diet.
The ACC also recommends1:
- Maintaining an optimal weight (a 1-kg reduction in weight is associated with a 1-mm Hg reduction in BP).
- Eating a healthy diet rich in fruits, vegetables, whole grains, and low-fat dairy products with reduced saturated and total fat.
- Regular aerobic physical activity 90 to 150 min/wk.
- Moderation in alcohol consumption, with men limiting consumption ≤ 2 drinks/d and women limiting consumption to ≤ 1 drink/d.
- Smoking cessation.
Most adults in the US have too much sodium and too little potassium in their daily diet. Diets high in sodium and low in potassium increase the risk of hypertension. In turn, this increases the risk of cardiovascular disease, including myocardial infarction and stroke. Many personal choices and societal factors contribute to our current imbalanced and unhealthy diet, rich in sodium and deficient in potassium. Our best approach to improve health and reduce cardiovascular disease is to guide people to modify unhealthy lifestyle behaviors.17 For patients who are ready to change, a counseling intervention using the 5 A’s (including assess risk behaviors, advise change, agree on goals/action plan, assist with treatment, and arrange follow-up) has been shown to result in improved dietary choices, increased physical activity, and reduced use of tobacco products.18 ●
Sodium intake and pregnancy-associated hypertension: Is there a link?
Two randomized clinical trials completed in the 1990s, comparing a low-sodium and a standard diet, showed no effect of reducing sodium intake by 32% and 57% on the risk of developing preeclampsia.1,2 Based on these 2 studies, a Cochrane review concluded that during pregnancy salt consumption should remain a matter of personal preference.3 Three recent observational studies report a relationship between sodium intake and the risk of developing pregnancy-associated hypertension.
In a study of 66,651 singleton pregnancies in the Danish Birth Cohort, participants with the greatest daily sodium intake, ranging from 3,520 to 7,520 mg/d had a 54% increased risk of developing gestational hypertension (95% confidence interval [CI], 16%–104%) and a 20% increased risk of developing preeclampsia (95% CI, 1%–42%).4 Another cohort study also reported that elevated sodium chloride intake was associated with an increased risk of developing preeclampsia.5 In one study, among patients with preeclampsia, those with lower urinary sodium to potassium ratio were less likely to develop severe preeclampsia.6 In a pregnant rat model, high salt intake is associated with a severe increase in blood pressure, the development of proteinuria, and an increase in circulating plasma soluble fmslike tyrosine-kinase 1 (sFlt-1)—changes also seen in preeclampsia.7 Pregnancy associated hypertension may not be as “salt sensitive” as chronic hypertension.
Future research could explore the effect of dietary sodium and potassium intake on the risk of developing severe hypertension during pregnancy in patients with chronic hypertension.
References
1. Knuist M, Bonsel GJ, Zondervan HA, et al. Low sodium diet and pregnancy-induced hypertension, a multicenter randomised controlled trial. Brit J Obstet Gynecol. 1998;105:430-434.
2. van der Maten GD, van Raaij JMA, Visman L, et al. Low-sodium in pregnancy: effects on blood pressure and maternal nutritional status. Brit J Nutr. 1997;77:703-720.
3. Duley L, Henderson-Smart DJ, Meher S. Altered dietary salt for preventing pre-eclampsia, and its complications. Cochrane Database Syst Rev. 2005;CD005548.
4. Arvizu, M, Bjerregaard AA, Madsen MTB, et al. Sodium intake during pregnancy, but not other diet recommendations aimed at preventing cardiovascular disease, is positively related to risk of hypertensive disorders of pregnancy. J Nutr. 2020;150:159-166.
5. Birukov A, Andersen LB, Herse F, et al. Aldosterone, salt and potassium intakes as predictors of pregnancy outcome, including preeclampsia. Hypertension. 2019;74:391-398.
6. Yilmaz ZV, Akkas E, Turkmen GG, et al. Dietary sodium and potassium intake were associated with hypertension, kidney damage and adverse perinatal outcome in pregnant women with preeclampsia. Hypertension Preg. 2017;36:77-83.
7. Gillis EE, Williams JM, Garrett MR, et al. The Dahl salt-sensitive rat is a spontaneous model of superimposed preeclampsia. Am J Physiol Regul Integr Comp Physiol. 2015;309:R62-70.