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Sodium study should be taken with a large pinch of salt

A recent article has questioned received wisdom regarding the adverse impact of salt on health. Unfortunately, naïve researchers and journal editors looking to stir up a controversy are confusing this…

People who exercise have a smaller risk of heart attacks despite larger salt intake. lululemon athletica/flickr

A recent article has questioned received wisdom regarding the adverse impact of salt on health. Unfortunately, naïve researchers and journal editors looking to stir up a controversy are confusing this important public health issue.

Should we really believe a study suggesting we turn to the salt cellar to protect us from strokes and heart attacks?

The answer is, most certainly, no.

Dubious science

The Journal of the American Medical Association (JAMA) paper contends that men and women with lower levels of salt consumption have greater risks of dying from cardiovascular diseases.

But this study has serious limitations.

Cohort studies of dietary risk factors are notoriously difficult to do well and require particularly sound epidemiological knowledge, very careful analysis and rigorous assessment of possible confounding factors.

Uncontrolled complexities in the data can easily lead authors and readers to draw the wrong conclusions.

To understand the type of problem this causes, consider the interplay between salt intake, physical activity and heart attacks:

Physically-active people have a reduced risk of heart attack because they exercise. But physically-active people also eat more food and therefore have a greater salt intake. So if we see an association between high salt intake and good health, what does it mean?

More likely than not, it reflects the well-established protective effects of exercise – not some newly-discovered benefit from salt.

One hopes that confounded research gets weeded out by reputable journals with professional editorial staff, who have access to good reviewers.

Particularly if a study also has a highly-skewed sample selection, poor measurement of salt intake and is based on just a few tens of deaths – 84, in this case, out of less than 4,000 participants.

But as we see here, things can slip between the cracks. Or perhaps newsworthiness can trump science, even at the JAMA.

Regardless of the cause, this JAMA study is an inconsequential report that adds little to the existing evidence base.

It should not change doctors' advice to patients, it should not change health policy and, if not for e-publishing, it would soon be consigned to the dusty archives.

For a real understanding of the science, readers should look to one of the many excellent summary reports that comprehensively and critically appraisal the data.

With multiple national and international bodies recommending the implementation of salt reduction programs, the real question is not whether we should be doing it, but how we should be doing it.

Salt in the Australian diet

It’s not just poor research and middling journalism that are holding back salt reduction in Australia.

Government and food industry lassitude is delivering glacial progress and weak commitments even though salt reduction promises huge health gains, at no risk and almost no cost.

How could it possibly be so hard?

Even the food industry, historically the greatest antagonist to salt reduction efforts, no longer argues about the need to remove salt from foods – only how much should be taken out and how quickly.

Several large corporations are already well-advanced in their efforts and are to be commended for this.

The industry umbrella organisation, the Australian Food and Grocery Council and the Federal Government are now the main impediments to better food policy in Australia.

The former, working to the lowest common denominator of its many members, systematically waters down every proposal. And the latter is unwilling to take the stand required to change this.

This is disappointing because it would require little money and little effort on either part to bring about change that would avert thousands of heart attacks and strokes each year.

That turning things around need not be problematic has been clearly demonstrated in the United Kingdom. The same sort of program advocated for Australia has brought about much reduced salt levels in foods and lower average salt consumption across the population.

Thousands of premature deaths are now averted each year at the cost of just a few million pounds. And no one went out of business or lost their parliamentary seat as a consequence.

Finally, don’t be conned into thinking this is a “salt war”. It’s not.

There are no great armies pitched against each other firing mighty salvos of contradictory science: just a sceptical few with an axe to grind sniping around the edges, using average science with dodgy findings to make a splash.

Read a different viewpoint of the JAMA article: Four seasons in one day: getting the right dose of salt

Are you confused by conflicting reports on salt intake? Share your thoughts below.