Science & Nutrition

Lancet paper blasts Cochrane salt study

01-Aug-2011
Last updated the 09-Mar-2012 at 18:31 GMT - By Nathan Gray
Reducing salt intake can lead to 'a significant reduction in cardiovascular events' according to the re-analysis of the Cochrane data.
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Commentary in The Lancet, along with a new analysis of the data, has slammed the recent Cochrane review that claimed salt reduction had no effect on strokes or heart attacks.

The re-analysis of the same data in the Cochrane review, published in the Lancet, finds a significant reduction in cardiovascular events, including a 20 per cent fall in the risk of stroke and heart attack from a reduction of 2 grams of salt per day.

The review, from Dr Rod Taylor and colleagues (reported by FoodNavigator here), stated that “Cutting down on the amount of salt has no clear benefits in terms of likelihood of dying or experiencing cardiovascular disease,” whilst a press release sent by the Cochrane Library warned: “Cutting down on salt does not reduce your chance of dying”.

“Both of these statements are incorrect,” said the authors of the re-analysis.

“Contrary to the claims by Taylor and colleagues and many press headlines, these new results, along with all the other evidence, clearly demonstrate that a reduction in the whole of the UK population and worldwide, is immensely important,” said Professor Graham MacGregor of the Wolfson Institute, and Chairman of World Action on Salt and Health (WASH), one of the authors of the re-analysis.

“In our view, Taylor and colleagues’ Cochrane review and the accompanying press release reflect poorly on the reputation of The Cochrane Library and the authors. The press release and the paper have seriously misled the press and thereby the public,” said the authors.

Evidence

Professor Francesco Cappuccio, head of the World Health Organization Collaborating Centre for Nutrition at the University of Warwick said that the benefits of salt reduction are “clear and consistent.”

“The findings from the Cochrane review do not indicate that salt reduction does not reduce hypertension and cardiovascular disease. Indeed, a correct reanalysis confirms the benefits shown by previous studies,” said Cappuccio.

“Therefore, the publication does not change the priorities outlined … for a population reduction in salt intake to prevent heart attacks and strokes,” he added.

MacGregor and his colleagues added that the totality of evidence, including epidemiological studies, animal studies, randomised trials, and outcome studies, “all show the substantial benefits in reducing the average intake of salt.”

The researchers highlight that many countries have already adopted policies to reduce salt intake by persuading the food industry to reformulate food with less salt, and encouraging the population to use less salt at the table and in home cooking.

“A reduction in population salt intake will have major beneficial effects on health along with major cost savings in all countries around the world,” said the researchers.

Impractical

MacGregor and his colleagues explained that the Cochrane review’s calls for further large, long term, randomised trials of salt reduction on clinical outcomes would be ‘impractical’.

“According to their own calculations, at least 2500 cardiovascular events need to be obtained to detect a 10 per cent reduction … This would require randomisation of about 28 000 participants to a low or high salt intake and then maintenance of the two separate diets for at least 5 years,” said the researchers.

“Such a trial is impractical because of logistical and financial constraints, and the ethical issues of putting a group of people on a high salt diet for so many years,” they added.

Consensus Action on Salt and Health (CASH) campaign director Katharine Jenner, added to the criticism, telling FoodNavigator that “there is no sense in waiting for further trials before progressing with an international salt reduction programme, which will immediately save many thousands of lives.”

Source: The Lancet
Volume 378, Issue 9789, Pages 380 - 382, doi: 10.1016/S0140-6736(11)61174-4
“Salt reduction lowers cardiovascular risk: meta-analysis of outcome trials”
Authors: F.J. He, G.A. MacGregor

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