Is population-wide salt reduction necessary?

By Caroline SCOTT-THOMAS contact

- Last updated on GMT

How suitable is current salt reduction policy?
How suitable is current salt reduction policy?

Related tags: Blood pressure

Despite decades of research and debate, there are still questions about the suitability of population-wide salt reduction. Can some people safely consume more salt than others?

The short answer is yes. Some people are more sensitive to salt, including certain ethnic groups, older people, and other groups with a high incidence of hypertension. Salt restriction is important for those with heart conditions, certain types of kidney and liver disease, as well as those with high blood pressure or at risk of high blood pressure. But for others, strict salt restriction may be less important.

That said, most people consume far more than the 5 g per day recommended by the World Health Organisation – an average of 8 to 12 g in Europe – and the WHO says reducing intake to 5 g per day is good advice for everyone.

One of the main arguments for population-wide salt reduction is that the link between reduced salt intake and reduced blood pressure is well established – through population-based studies like the Intersalt study​ – and high blood pressure is a major risk factor for heart disease and stroke.

On the other side of the debate, some argue that just because A leads to B and B leads to C, that doesn’t necessarily mean that A (high salt intake) leads to C (higher risk of heart disease and stroke).

But while it’s easy to test for whether someone has high blood pressure, it’s not always easy to pinpoint whether someone is at risk of​ high blood pressure, so policymakers have tended to take a precautionary approach and have recommended reduced salt intake for the entire population.

Potential harm?

Purely from a health perspective, this wouldn’t matter if there were no potential downsides to population-wide salt reduction, but there are scientists who suggest there could be.

In particular, a major review​ of 167 randomised controlled trials published in the Cochrane Library​ and the American Journal of Hypertension​ in 2011 challenged the current status quo on salt reduction policy. The Danish researchers found that although cutting sodium consumption did decrease blood pressure, it also tended to increase levels of hormones, cholesterol and triglycerides, which are all thought to be risk factors for heart disease too.

Lead author Dr Niels Graudal, senior consultant in internal medicine and rheumatology at Copenhagen University Hospital, said at the time: "In my opinion, people should generally not worry about their salt intake.”

The researchers called for long-term trials and more studies to work out if the benefits of salt reduction outweighed potential harms.

‘No signal on clinical events’

However, responding to the review, Dr Larry Appel, director of the Welch Center for Prevention, Epidemiology and Clinical Research at Johns Hopkins Medical Institutions, said that it was hard to reconcile existing data with the idea that salt reduction might be harmful.

“Importantly – there is NO signal from sodium reduction trials on clinical events,” ​he said via email.

Additionally, there is some evidence that population-wide salt reduction may be associated with lower incidence of heart disease and stroke.

In Finland, where a salt reduction campaign began in the 1970s, average consumption of salt fell by about a third over 30 years, to about 7 g a day for women and 8.3 g a day for men.  According to a 2006 study published in Progress in Cardiovascular Diseases​, during the same time period, average blood pressure (both systolic and diastolic) fell by more than 10–mm Hg, and there was a 75% to 80% decrease in both stroke and coronary heart disease mortality in Finland.

Dr Appel commented: I can’t attribute all of the benefit to sodium reduction, but again it is hard to believe that there would be a net benefit from the intervention if indeed sodium reduction were harmful.”

The bottom line?

The suitability of population-wide salt reduction policy continues to attract strong debate among academics, but for those with hypertension, heart disease and many other conditions, cutting salt continues to be a first step in controlling blood pressure.

For everyone else, for now at least, the old advice remains: Moderation in all things – including salt.

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4 comments

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salt is not an independent risk factor

Posted by Mythbuster,

The debate on salt between the evidence based scientists and the anti-salt lobbyists. It has raged because there is no conclusive evidence of a direct independent association, becasue it isn't indepenedent. Weakening of industry influence due to food scares has given the lobbyists the upper hand in recent years as they are driven by the salt mantra. This has not done nutrition science any favours and even undermines nutrition as a science.

School level students were (hopefully still are) taught about the exchange of sodium and potassium in the loop of Henley in the kidney. yes this seems to have been forgotten by the nutritionists. If potassium is at adequate levels than the body excretes excess sodium through the kidney. This is restricted through disease of the kidney, redeuced function (maybe with age) or inadequate potassium intake (largely fruit and vegetable, including potatoes).

Any study looking at the impact of sodium on blood pressure needs to ensaure it includes potassium status. Potassium supplementation is often more effective at reducing blood pressure than soidum restricition. Why? (see above). So why didn't the DASH-Sodium trial pivotal to the salt arguement control potassium? Why is intersalt, so dependent on its outlier figures to show a relationship? Because sodium only has an effect when kidney function is impaired (or hasn't got adequate potassium availability.

Measuring blood pressure and urinary sodium and potassium are relatively easy. Why do the government agencies pushing sodium restricition not look at these measures for relationships in their surveys?

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Are you serious?

Posted by nisakiman,

@ Jordi

Are you seriously saying that every man, woman and child on this planet has exactly the same dietary requirements? If so, your simplistic approach is risible. As the article above points out, correlation does not mean causation, and only a fool will even consider that dietary requirements can be standardised across a population, particularly an ethnically diverse one.

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Sodium consumption and its complexity

Posted by Daniel Best /BEST VANTAGE Inc.,

This article's posting is very timely and raises very important questions about conventional thinking. Sodium's relationship to blood pressure is modulated by many dietary and non-dietary factors, including intakes of other minerals (potassium, calcium, magnesium), the interplay of which is still poorly understood. Nutritionists risk discrediting their /our profession when they /we make hard-and-fast generalizations about physiologically heterogenous and complex populations that end up having to be debunked as more data comes to the fore. Well done, Ms. Scott-Thomas.

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