Salt sensitivity
Current evidence supports a recommendation for moderate sodium intake in the general population (3-5 g/day). Persons with hypertension should consume salt at the lower end of that range. Some dietary guidelines recommend consuming less than 2,300 mg dietary sodium per day for persons aged 14 years or older and less for persons aged 2-13 years. Although low sodium intake (< 2.0 g/day) has been achieved in short-term clinical trials, sustained low sodium intake has not been achieved in any of the longer-term clinical trials (duration > 6 months).
The controversy continues as to the relationship between low sodium intake and blood pressure or cardiovascular diseases. Most studies show that both in individuals with hypertension and those without, blood pressure is reduced by consuming less sodium. However, it is not necessarily lowered by reducing sodium intake (< 3-5 g/day). With a sodium-rich diet, most normotensive individuals experienced a minimal change in mean arterial pressure; for many individuals with hypertension, the values increased by about 4 mm Hg. In addition, among individuals with hypertension who are “salt sensitive,” arterial pressure can increase by > 10 mm Hg in response to high sodium intake.
The effect of potassium
Replacing some of the sodium chloride in regular salt with potassium chloride may mitigate some of salt’s harmful cardiovascular effects. Indeed, salt substitutes that have reduced sodium levels and increased potassium levels have been shown to lower blood pressure.
In one trial, researchers enrolled over 20,000 persons from 600 villages in rural China and compared the use of regular salt (100% sodium chloride) with the use of a salt substitute (75% sodium chloride and 25% potassium chloride by mass).
The participants were at high risk for stroke, cardiovascular events, and death. The mean duration of follow-up was 4.74 years. The results were surprising. The rate of stroke was lower with the salt substitute than with regular salt (29.14 events vs. 33.65 events per 1,000 person-years; rate ratio, 0.86; 95% CI, 0.77-0.96; P = .006), as were the rates of major cardiovascular events and death from any cause. The rate of serious adverse events attributed to hyperkalemia was not significantly higher with the salt substitute than with regular salt.
Although there is an ongoing debate about the extent of salt’s effects on the cardiovascular system, there is no doubt that in most places in the world, people are consuming more salt than the body needs.
A lot depends upon the kind of diet consumed by a particular population. Processed food is rarely used in rural areas, such as those involved in the above-mentioned trial, with dietary sodium chloride being added while preparing food at home. This is a determining factor with regard to cardiovascular outcomes, but it cannot be generalized to other social-environmental settings.
In much of the world, commercial food preservation introduces a lot of sodium chloride into the diet, and most salt intake could not be fully attributed to the use of salt substitutes. Indeed, by comparing the sodium content of cereal-based products currently sold on the Italian market with the respective benchmarks proposed by the World Health Organization, researchers found that for most items, the sodium content is much higher than the benchmarks, especially with flatbreads, leavened breads, and crackers/savory biscuits. This shows that there is work to be done to achieve the World Health Organization/United Nations objective of a 30% global reduction in sodium intake by 2025.
This article was translated from Univadis Italy. A version of this article first appeared on Medscape.com.