Commentary: Sodium and blood pressure in the Intersalt study and other studies--in reply to the Salt Institute

The Salt Institute continues to misrepresent the findings of Intersalt (and other studies) on salt and blood pressure, and the availability of Intersalt data. It not only incorrectly attempts to discredit the Intersalt finding that average population salt intake is positively related to slope of blood pressure with age1; it also ignores or misrepresents two other important results—the positive relations between sodium excretion of individuals and their blood pressure (found in over 10 000 adults), and the positive association of average population sodium intake with average blood pressure and prevalence of hypertension across the 52 populations in the Intersalt study. The institute's statement that “the primary Intersalt hypotheses were largely negative” is incorrect. The Salt Institute was clearly not happy with the implications of the original Intersalt findings on salt intake and blood pressure slope with age—an additional 9 mm Hg higher systolic blood pressure over 30 years (for example, from age 25 to 55) for an additional 100 mmol population sodium intake. It therefore requested that the Intersalt group perform several additional analyses on the slope of blood pressure with age, using statistical methods suggested by the institute. These were done, and all analyses again showed a significant relation of average population salt intake (as assessed by average 24 hour urinary sodium excretion) and population blood pressure slope with age.2 The analyses included those that had controlled for pressure in young adults (ages 20-29). Findings were similar to the original results: the higher the population salt intake, the greater the upward slope of blood pressure with age—for all 52 population samples and also when the four low sodium samples were excluded (fig 1). These findings were made …