The epidemiology of salt and hypertension

Abstract

The relationship between salt intake and blood pressure was once highly controversial. Early comparisons of populations did support the salt hypothesis but were difficult to interpret because of unmeasured confounding variables. However, the INTERSALT project, published in 1988 overcame many of these problems and reported within - and between - population gradients of sodium excretion and blood pressure or the rise in blood pressure with advancing age. Of the five long-term follow-up studies of salt intake and cardiovascular disease, two suggested that a low salt intake might be harmful. These studies are however open to much criticism. The three other studies reported positive relationships between salt intake and stroke or heart attack. Whilst there is little doubt that salt restriction lowers blood pressure in hypertensive patients, there remains some uncertainty whether any effect is seen in normotensives. The effects, if present, are small (reducing systolic pressure by about 2 mmHg) and not clinically useful, although if applied on a population-wide basis they might reduce the prevalence of hypertension by about 17 %. In many countries food producers and food standards agencies are beginning to respond by cutting the salt content of processed foods.

Urinary sodium and potassium excretion and risk of hypertension in Chinese: report from a community-based cohort study in Taiwan

“…Furthermore, we did not estimate the processed foods with sodium intake and evaluate the different contents of foods. Methods for sodium intake from a 24-h dietary recall or a food frequency questionnaire are inaccurate measures of usual intake for the general population [40]. Accordingly, we used the secondary morning voiding urine amount as the surrogate for calculating 24-h urine sodium and potassium excretion [12].…”

Salt craving: The psychobiology of pathogenic sodium intake

“…In the context of our evolutionary history, the addition of large quantities of salt to the diet is a recent phenomenon (approximately the last 5000 years). It appears that evolution has rendered us best adapted to handle far less sodium than we now consume, perhaps less than one-tenth as was the case with our hunter-gatherer ancestors [7,31,33,34,38]. A strictly vegetarian diet contains about 750 mg of salt per day [34].…”

The straw men of the salt lobby

“…In addition, we eat much more salt than we actually need. In this issue we have two of the leading evangelists arguing for different sides of the debate -Beevers promoting the view of the anti-salt lobby that the public should be advised to eat less salt [1], and Alderman that this policy is ill-advised [2]. Beevers makes much play of the fact that my father, Sir George Pickering, was one of the leading critics of the salt hypothesis, but that was 30 years ago, and much has changed since then.…”