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Experts crying foul over conclusion that salt consumption is safe August 2, 2011

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Table salt and peppercorns.


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 LancetDr 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 by heartwire , 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.

Misleading Public Messages?

In an interview with heartwire , MacGregor, who is also chair of both the Consensus Action on Salt and Healthand the World Action on Salt and Health, said he and his coauthor felt Taylor et al’s conclusions in the paper itself were measured. But they take issue with both the “Plain Language Summary” printed within the main article and with a press release sent out by the publisher.

“The press release and the paper have seriously misled the press and thereby the public,” they write. “For example, in the UK the Daily Express front-page headline read, ‘Now salt is safe to eat–Health fascists proved wrong after lecturing us all for years,’ and there were similar headlines throughout the world.”

“In actual fact, the findings we have when we reanalyze the data are the exact opposite of what the others conclude in their attention-grabbing headlines,” MacGregor told heartwire .

An Urgent Retort

Asked why their comment was sent to the Lancet rather than one of the two publications in which the Taylor et al paper was published, MacGregor cited the need for a swift, high-profile response.

“Obviously this is somewhat urgent–this caused headline news around the world, and the [salt-industry trade association] SALT Institute has a huge amount on its website about this,” he said. “We wanted to get this correction in [print] very quickly and get it some publicity, because it’s obviously totally wrong to claim salt reduction is not beneficial.” In fact, he points out, Taylor et al’s review “doesn’t say that; it says we need more evidence. We say it is [beneficial]; we’ve done this reanalysis, and we’ve got the evidence. In fact, all the evidence about salt is overwhelming. . . . It all shows that salt is a major factor bringing up our blood pressure.”

Asked to respond to He and MacGregor’s Comment, Dr Rod Taylor (University of Exeter, UK) told heartwirethat he and his coauthors are preparing a “formal letter in response” that they plan to submit to the Lancet, and “We’d rather make use of our letter as our communication vehicle in this case.”

He and MacGregor declare they have no conflicts of interest.

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