The INTERSALT Study was a 1988 international observational study which investigated the link between dietary salt, as measured by urinary excretion, and blood pressure. The study was based on a sample of 10,079 men and women aged 20âÂÂ59 sampled from 52 populations around the world. The authors of the study provided a widespread international investigation of the correlation between dietary salt intake and blood pressure in a systematic and standardized way with regards for relevant confounding variables, beyond just age and sex.
The study found a significant direct relationship between dietary salt intake, the urinary sodium:potassium ratio and systolic blood pressure, and between salt intake and the slope of blood pressure with age â both for all 52 populations, and for 48 populations excluding four low-sodium populations (Yanomamo and Xingu Indians of Brazil, Papua New Guinea and rural Kenya).
The results were disputed by the Salt Institute (the salt producers' trade organisation, since disbanded), who demanded that the results be handed over for re-analysis. A re-analysis was published in 1996 and the results were the same. The results have since been confirmed by the TOHP I and TOHP II studies, trials of salt reduction and blood pressure in chimpanzees, meta-analyses of the human clinical trial data and the SSaSS trial of salt substitute and cardiovascular disease.