CASH Comment – The Cochrane Collaboration

Reduced dietary salt for the prevention of cardiovascular disease (Review)

6th July 2011

Katharine Jenner, Campaign Director of Consensus Action on Salt and Health, says: 

It is very disappointing that the message from this small review suggests 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.  

This review is based on just 7 studies that were not designed to test the effects of sodium reduction interventions on cardiovascular events and mortality.  

However the authors have taken the view that, due to a lack of outcome trials measuring cardiovascular mortality, dietary salt restriction may not have any benefits.  In fact, there are no robust outcome trials for other chronic exposures, such as smoking, excess weight and insufficient fruit & vegetable intakes either, due to the complexities (cost, duration, ethical considerations, compliance and duration) 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.  

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.

With specific reference to the questionable inclusion of the heart failure study looking at heart failure patients on diuretics; Dr Feng He states in her paper:

“It is important to note that, in one of the included trials […] (Paterna et al 2008), patients were on the high-dose diuretics furosemide, angiotensin-converting enzyme inhibitor and spironolactone, and they were already on the verge of sodium and water depletion. It is therefore not surprising that a lower salt intake is harmful under such circumstances, particularly when no attempt was made to lower the dose of furosemide or spironolactone.”

Professor Rod Taylor, the lead researcher of the review, is 'completely dismayed' at the headlines that distort the message of his research published today.  Having spoken to BBC Scotland, and to CASH, he clarified that the review looked at studies where people were advised to reduce salt intake compared to those who were not and found no differences, this is not because reduced salt doesn’t have an effect but because it’s hard to reduce salt intake for a long time.  He stated that people should continue to strive to reduce their salt intake to reduce their blood pressure, but that dietary advice alone is not enough, calling for further government and industry action.

 Click here to read the Cochrane Review