[Effect of salt-restriction on blood pressure. A review over epidemiological studies and a meta-analysis of clinically controlled studies].

Cross-section regression analyses of some of the world's populations suggest a direct linear relationship between mean blood pressure and mean salt-intake. Since such investigations have hitherto been partly based on information about dietary salt intake, which is a questionable measure, we performed an analysis including 28 male populations and an analysis including 21 female populations solely based on 24 hour sodium urinary excretion. The regression analysis confirmed that a direct linear relationship between blood pressure and 24 hour sodium urinary excretion existed, since the blood pressure in a population was about 7 mmHg/6 mmHg higher than in a population which consumed 100 mmol less salt. We were, however, not able to correct for confounders. This was done in the recently published "Intersalt" study in which the linear relationship between median blood pressure and median salt intake disappeared after correction for weight and alcohol intake. From the regression coefficients from "Intersalt" it can be deduced that a reduction in salt intake from 150 mmol to 75 mmol may reduce blood pressure by 1.6/0.05 mmHg. Most epidemiological studies have not been able to demonstrate a correlation between salt intake and blood pressure within population. Still, on the basis of uncontrolled clinical studies it has been claimed that salt-restriction may reduce blood pressure. Consequently we also performed a meta-analysis of 15 controlled clinical trials dealing with the effect of salt-restriction on blood pressure within a population. This meta-analysis including 704 patients showed that a reduction in average salt intake from 150 mmol to 75 mmol may reduce blood pressure by 2.4/1.4 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)