Should you really be eating less salt?

By Marika Sboros

Should you eat less salt? The Heart and Stroke Foundation of SA (HSFSA) and the Association for Dietetics in SA (ADSA) believe you should. So do many experts globally, including Harvard Medical School researchers. . They say lowering salt intake protects your heart and blood vessels and prevents premature death from heart attack and stroke.

There are just as many medical experts who say the exact opposite – that a low-salt diet actually increases your risk of dying prematurely from cardiovascular disease (heart attack and stroke). 

Current guidelines from the World Health Organisation, the American Heart Association and heart foundations around the world recommend daily dietary sodium targets between 1,500 and 2,300 milligrams or lower. That’s well below the average US daily consumption of close to 3,600 milligrams, and in SA, where experts estimate it is even higher at around 4,000 milligrams of sodium a day.

Salt is also called sodium chloride, and food labels may only give the sodium figure. To work out how much salt that is, multiply the sodium figure by 2.5.

During Salt Awareness Week 2013, the HSFSA and ADSA  banded together with other interest groups  to launch a new lobby group, Salt Watch, to raise awareness of excess sodium in the diet, and how best to lower it.

Experts say one way in general is by following official dietary guidelines that favour a low-salt approach, and in particular the “DASH” diet. That’s short for the low-sodium Dietary Approaches to Stop Hypertension diet that’s high in fruits, vegetables, and whole grains, moderately high in nuts and low-fat dairy products, and very low in red and processed meats.

But is there really any science behind low-salt advice? It depends who you talk to.

HSFSA CEO Dr Vash Mungal-Singh says its advice is based on “the totality of evidence to date, which supports the link between excess sodium consumption, hypertension and cardiovascular endpoints”. She agrees that too little salt can be bad for health, but says the real problem is overconsumption of salt, especially among South Africans.

“We are eating mostly highly processed foods, that  contain hidden salt and don’t realise just how much we are consuming,” Mungal-Singh says. “The problem is that up to 60% of this salt is hidden in products.”

Reducing excess sodium intake is also in line with the World Health Organisation’s Global Action Plan for the Prevention and Control of Non-Communicable Diseases, she says.

ADSA says evidence supporting the direct relationship between hypertension and salt consumption is “overwhelming with various study designs supporting this relationship^”.  It includes animal studies, genetic studies, large population-based studies, meta-analyses and treatment studies.

ADSA supports South Africa’s food-based dietary guidelines, which is not all that surprising, since its members draw them up. It says the guidelines recommend sparing use of salt and foods high in salt, and provide “a full technical support paper (with 73 references) for this recommendation”.

 South Africa’s high hypertension rates, consumption of high-salt foods and evidence from other countries, as well as literature, “contributed to the science that drove the South African Department of Health to implement salt reduction legislation in 2013”, ADSA says.

ADSA says salt reduction in South Africa “holds financial benefits”, and is expected to have the same cost-effectiveness as seen in other countries: “Salt reduction in SA (only in bread, margarine, gravy and soup) is expected to result in 7400 fewer cardiovascular disease deaths and 4300 less nonfatal strokes per year leading to cost savings of up to R300 million. “

The next five to 10 years will be “crucial in monitoring the salt reduction legislation and its effect on the population’s health, specifically hypertension,” ADSA says.

Experts on the other side of this scientific fence, including cardiologists, are not so sanguine. They say conventional “wisdom” on salt reduction is not so wise after all, and the totality of scientific evidence simply isn’t there to show less morbidity or improved survival from eating less salt.

It’s probably not coincidental that these experts have few, if any, ties to food and pharmaceutical companies compared with doctors, dietitians and lobby groups who enthusiastically promote low-salt diets.

Experts who don’t endorse a low-salt diet are also not fans of the hugely influential US official dietary guidelines that are religiously followed by countries around the world, including SA. The US guidelines were updated in January. They were quickly shown once again to be short on science – and long on conflicts of interests. In other words, the guidelines are the fruits of research by scientists, doctors and others who are a little too close for comfort to food and drug companies. For information on that, read US investigative writer Nina Teicholz’s report in the BMJ last year in which she poses the question: The scientific report guiding the US dietary guidelines: is it scientific? No prizes for guessing the answer.

Another international expert who is skeptical of the “wisdom” of a low-sodium diet  for otherwise healthy people in general, and in particular for people who already have some form of cardiovascular disease (CVD), is Canadian nephrologist (kidney specialist) Dr Jason Fung.

Fung says reducing salt is not necessary except in the case of advanced renal or heart failure: “Essentially, I think  we are eating the right amount of salt and cutting it down has no benefits. It’s simply a waste of energy.”

Fung also says concerns over health risks of low-salt diets are not new, and one reason for conflicting opinions is the common phenomenon known as “confirmation bias”. We all have it, he says, and it happens when we  “have a certain view of the world, and tend to view all new information through that filter. It’s like looking at the world through rose-coloured glasses.” 

Confirmation bias has led researchers to conclude that low-salt diets are beneficial when their data show a very different picture, he says.

Fung says there’s no denying a low-salt diet can lower blood pressure. Hypertension (high blood pressure) is a major risk for heart attack and stroke, and is known as the “silent killer” because it often doesn’t show any symptoms, and many people are walking around unaware that they have it. However, the more important questionis the health outcomes of lowering blood pressure.

Therein lies the real salty rub: Fung says there is no evidence to show a correlation between low-salt and increased  life expectancy, or that for most people, a low-salt diet does any good at all. 

On the contrary, in a lecture in 2013 available on Youtube, Fung  says there is good evidence to show a low-salt diet can be actively bad, and that the less salt you eat, the higher your risk of cardiovascular and other serious health problems.

Fung refers to the 2013 report from the US Institute of Medicine that  advises Congress on health issues, which found no evidence that cutting sodium intake below the recommended 2,300 milligrams reduced risk of cardiovascular disease.

More recently, a 2014 study in the New England Journal of Medicine  tracked more than 100,000 people from 17 countries over an average of more than three years, and similarly found that those consuming fewer than 3,000 milligrams of sodium a day had a 27% higher risk of death or a serious event such as a heart attack or stroke in that period than those whose intake was estimated at 3,000 to 6,000 milligrams. The study did show that risk of death or other major events increased with intake above 6,000 milligrams.

The findings build on a vast body of research to show that aggressively low sodium targets are for the most part not beneficial, and can actively be harmful.

Fung explains one mechanism of action by which salt reduction can increase your risk of dying prematurely from CVD. It increases levels of certain hormones in the body, including plasma renin, noradrenalin and aldosterone, and that’s not good news. It can lead to what is known as “cardiovascular remodeling” –  defined as “changes in the heart’s size and shape that occur in response to cardiac disease or cardiac damage”. 

US expert Dr Richard Feinman, professor of cell biology at SUNY (State University of New York) Medical Centre, is similarly dismissive of sweeping recommendations to reduce dietary salt.

“As in all these recommendations, if they are meaningful there should be almost unanimous agreement whereas there is widespread disagreement,” Feinman says.

If experts really wanted to recommend something for people in general to do,  it should be to get their blood pressure tested and see if they really do need to reduce salt, he says.

“I’m  not aware of any direct correlation but at least we would be talking about who needs to reduce salt,” Feinman says.

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