Effects of low sodium diet versus high sodium diet on blood pressure, renin, aldosterone, catecholamines, cholesterols, and triglyceride

Jürgens G, Graudal NA

Summary

This review of short-term studies shows that in people with elevated blood pressure low salt diets lead to useful drops in blood pressure, but overall harms or benefits are not known.
We are commonly advised to cut down on salt. However, a pair of Cochrane reviews has found that there is little evidence for long-term benefit from reducing salt intake. This review looked at mostly short-term strategies to reduce salt intake. The other review (Hooper 2003) looked at long-term strategies to reduce the amount of salt in foods and drinks.
Advice about reducing salt intake did lower blood pressure but only by a small amount. It was not enough to expect an important health benefit. It is also very hard to keep to a low salt diet. However, the reduction was larger for people with high blood pressure. The studies were not designed to measure long-term health effects so, we don't know if low salt diets improve health outcomes.
The studies in which some people were given low salt diets and compared with others on a normal diet, found that the blood pressure did fall while the people were in the trial. But, it's not known if it stayed down after the trials. This means that the available evidence does not suggest that people with normal blood pressure should reduce the amount of salt they eat or drink. However, for people with high blood pressure low salt diet caused a larger reduction in blood pressure, and would be useful as part of a program to reduce blood pressure.
Most of the people who took part in the studies were Caucasians, but in the small number of non-Caucasians (mostly African) the blood pressure reduction was, if anything, greater. More research on salt intake is required, particularly in non-Caucasian populations.
See also the long-term salt review: Hooper 2003.