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Salt reductions may not reduce heart disease risk: Cochrane review

By Nathan Gray , 06-Jul-2011
Last updated on 06-Jul-2011 at 13:14 GMT2011-07-06T13:14:13Z

There is not yet enough evidence to show that reducing salt intake reduces the incidence of heart disease.
There is not yet enough evidence to show that reducing salt intake reduces the incidence of heart disease.

Moderate reductions in salt intake do not reduce the likelihood of dying or experiencing cardiovascular disease, according to a new Cochrane review.

The systematic review published by The Cochrane Library set out to assess whether advice to cut salt intakes altered the risk of death or cardiovascular disease. The authors, led by Professor Rod Taylor from Peninsula College of Medicine and Dentistry in the UK, found no strong evidence to support the idea that salt reduction reduces cardiovascular disease or all-cause mortality in people with normal or raised blood pressure.

“Intensive support and encouragement to reduce salt intake did lead to a reduction in salt eaten and a small reduction in blood pressure after more than six months … [However] there was not enough information to understand the effect of these changes in salt intake on deaths or cardiovascular disease,” said the authors.

Consensus Action on Salt and Health (CASH) campaign director Katharine Jenner, told FoodNavigator that it is “very disappointing” to see the message from the review indicates that salt reduction may not be beneficial.

“This is a completely inappropriate conclusion, given the strong evidence and the overwhelming public health consensus that salt raises blood pressure which leads to cardiovascular disease,” said Jenner.

Salt reduction

Taylor and colleagues noted that there is lots of evidence to suggest that reducing dietary salt intake reduces blood pressure.

“The relationship of salt intake to blood pressure is the basis for the belief that restriction in dietary sodium intake will prevent blood pressure related cardiovascular events,” they added.

As a result, current public health recommendations in many countries are to reduce salt intake by about half, to around five grams per day.

Intensive support and encouragement to reduce salt intake did lead to a reduction in salt eaten and a small reduction in blood pressure after more than six months,” said Taylor.

“What we wanted to see was whether this dietary change also reduced a person’s risk of dying or suffering from cardiovascular events,” he added.

Taylor and his colleagues also noted that an earlier Cochrane review of dietary advice, published in 2004, did not provide enough evidence to allow the researchers to draw conclusions about the effects of reducing salt intake on mortality or cardiovascular events.

Systematic review

The new review located seven studies, which included 6,489 participants – Thus giving a sufficiently large set of data to be able to start drawing conclusions, suggested the authors.

They found that for cardiovascular morbidity and all cause mortality in people with normal or raised blood pressure at baseline showed no strong evidence of benefit from salt intake restriction. Salt restriction did, however, increase the risk of death from all causes in those with congestive heart failure, reported the authors.

Taylor and his colleagues noted that despite collating more event data than previous systematic reviews, there is still insufficient evidence to suggest that moderate reductions in salt intake have beneficial effects on all cause mortality or the risk of cardiovascular disease.

CASH’s Jenner disagreed with the findings of the study, noting that there are no robust outcome trials for many other chronic exposures, including smoking, excess weight, and insufficient fruit and vegetable intakes, due to the complexities of undertaking such trials.

“The evidence against salt, as it is for smoking cessation, is so strong it would be highly unethical to conduct a large trial where people have to have a long term high salt intake,” she said.

Moderate effect?

“We believe that we didn’t see big benefits in this study because the people in the trials we analyzed only reduced their salt intake by a moderate amount, so the effect on blood pressure and heart disease was not large,” said Taylor.

“With governments setting ever lower targets for salt intake, and food manufacturers working to remove it from their products, it’s really important that we do some large research trials to get a full understanding of the benefits and risks of reducing salt intake,” he added.

However, Jenner told 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.”

“We are, however, pleased that this review recognises that reformulation by the food industry, rather than individual dietary advice, is the most cost-effective strategy for salt reduction in developed countries, and fully support the evaluation of such programmes,” she said.

Source: The Cochrane Library
Cochrane Database of Systematic Reviews, doi: 10.1002/14651858.CD009217
“Reduced dietary salt for the prevention of cardiovascular Disease”
Authors: R.S. Taylor, K.E. Ashton, T. Moxham, L. Hooper, S. Ebrahim

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