Cochrane salt/blood-pressure message blasted in the Lancet

Two preventive-medicine experts in the UK are crying foul over a recent and controversial meta-analysis that concluded cutting salt consumption would have no clear health benefits [1]. In a Comment published in the July 30, 2011 issue of the Lancet, Dr Feng J He (Queen Mary University, London, UK) and Dr Graham A MacGregor (Wolfson Institute of Preventive Medicine, Barts, London, UK) say that the meta-analysis published simultaneously by Taylor and colleagues in the Cochrane Review [2] and the American Journal of Hypertension [3] and press release that accompanied it "reflect poorly on the reputation of the Cochrane Library and the authors."

As previously reported, Taylor et al's meta-analysis included seven randomized controlled trials of dietary salt reduction in normotensives (three studies), hypertensives (two studies), a mixed population (one study), and one trial of patients with heart failure.

At follow-up, relative risks for all-cause mortality and cardiovascular mortality for both normotensives and hypertensives were only mildly to moderately reduced, and not to a statistically significant degree. In congestive heart failure patients, salt restriction actually significantly increased all-cause death.

He and MacGregor, in their Comment, reanalyze the same data but combined the normotensives and hypertensives. They also omitted the heart-failure trial—a group of "very ill" patients taking large doses of diuretics in whom salt restrictions would seldom be recommended, MacGregor observed. In the combined patient analysis, they find a now statistically significant 20% reduction in cardiovascular events and a nonsignificant reduction in all-cause mortality.

"The results of our reanalysis, contrary to the claims by Taylor and colleagues, support current public-health recommendations to reduce salt intake in the whole population," He and MacGregor conclude.