Salt and hypertension.

The salt hypothesis states that salt is a necessary condition for the genesis of essential hypertension; however, it is not a sufficient condition. Other factors---primarily genetics--are necessary for the expression of the disease. The arguments in favor of this still controversial subject originate from pathophysiology, evolution, history, pharmacology, experimental and clinical medicine, and epidemiology. Epidemiologic observations favoring the hypothesis mostly relate to comparisons between populations, and much less to comparisons within populations. The arguments against this hypothesis are related mostly to the well known difficulties of proving a within-population relationship of a relatively homogeneously distributed variable to an age-related variable (blood pressure). Mortality data derived from stomach cancer and stroke, compared within and between populations, provide only circumstantial, but nevertheless important, evidence in favor of the salt hypothesis. The strong, consistent, and independent association between stomach cancer and stroke mortality is best explained by the level of salt intake in the population. The observations made in Belgium over the last years are consistent with the salt hypothesis. A decrease in salt intake at the population level correlated with a marked decrease in stroke and stomach cancer mortality, larger than in any other European country, except Finland.