IT’S a perennial debate: do you really need to eat less salt or is this just advice doctors and dietitians dish up because they’ve always done so. Should you heed it or take it with a hefty pinch of salt? Here’s what experts say on both sides of a controversial scientific fence.
By Marika Sboros
Are you eating too much salt? Heart foundations and dietitians’ associations globally say you are. It’s practically hardwired into society that this is what you should do if you are concerned about your heart.
Other experts – including scientists at Harvard Medical School and the World Health Organisation – say the same thing: you should eat less salt for your heart’s sake. They say a low-sodium diet protects your heart and blood vessels and ..prevents premature death from heart attack and stroke.
Just as many medical experts have said the exact opposite for years. They say that far from being cardio-protective, a low-sodium diet actually increases your risk of cardiovascular disease (heart attack and stroke). They also say that going after salt is targeting the “wrong crystal”. Sugar is far more of a risk to heart and overall health .
Current guidelines from the World Health Organisation, the American Heart Association and heart foundations around the world set daily dietary sodium targets between 1,500 and 2,300 milligrams, well below the average US daily consumption of about 3,400 milligrams.
Salt is also called sodium chloride, and food labels may often only give the sodium figure. To work out how much salt that is, multiply the sodium figure by 2.5.
In the UK, the recommendation is that adults should eat no more than 2.4g of sodium daily, as this equals 6g of salt. In 2014, the average salt consumption for UK adults in 2014 was 8g a day.
Experts who favour the low-dietary-sodium approach say one way of doing that is to follow official dietary guidelines, and in particular what is known as the DASH diet. That’s short for the low-sodium Dietary Approaches to Stop Hypertension diet that is high in fruits, vegetables, and whole grains; moderately high in nuts and low-fat dairy products; and low in red and processed meats.
But is there really any science behind this advice? That depends on who you talk to.
In South Africa, the Heart and Stroke Foundation of SA (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 too, but says the real problem is overconsumption, especially among South Africans. To that end, the HSFSA has partnered with food giant Unilever to create a new “salt calculator”.
“We are eating mostly highly processed foods, that contain hidden salt and don’t realise just how much we are consuming,” Munghal-Singh says.
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.
ADSA heartily endorses that view, and says evidence supporting the direct relationship between hypertension and salt consumption is “overwhelming with various study designs supporting this relationship”. The research includes animal studies, genetic studies, large population-based studies, meta-analyses and treatment studies.
ADSA not surprisingly supports South Africa’s food-based dietary guidelines, since its members draw them up. It says the guidelines provide “a full technical support paper (with 73 references)” for its low-sodium 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.
Salt reduction in South Africa also holds financial benefits, says ADSA, and is expected to have the same cost-effectiveness as seen in other countries:
“Salt reduction in South Africa (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. “
ADSA says 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.”
Experts on the other side of this scientific fence, including cardiologists, are not so sanguine. They say conventional “wisdom” on salt reduction to prevent not just cardiovascular disease but other health problems, is not so wise after all. They say the totality of scientific evidence simply isn’t there to support the idea of 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 and dietitians who promote low-sodium diets vigorously. Or that they are not fans of the hugely influential US official dietary guidelines that are religiously followed by countries around the world, including South Africa. The US guidelines were updated in January, and were quickly shown once again to be woefully 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 more 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.
For even more, read a brilliant article by US science writer Gary Taubes in Science magazine nearly 20 years. Provocatively titled The (Political) Science of Salt, Taubes takes aim at the public health message, saying that “the data supporting universal salt reduction have never been compelling, nor has it ever been demonstrated that such a program would not have unforeseen negative side effects”.
Another top international expert who is scathing of the “wisdom” of a low-sodium diet – not just for otherwise healthy people in general, and in particular for people who already have some form of cardiovascular disease (CVD) – is US cardiovascular research scientist Dr James DiNicolantonio, of Saint Luke’s Mid America Heart Institute.
DiNicolantonio says experts who promote a low-salt diet are going after the “wrong white crystals”.
In a groundbreaking study in the BMJ Open Heart in 2014, he says sugar is far more important as the aetiology (cause) of hypertension and cardiometabolic disease.
Canadian nephrologist (kidney specialist) Dr Jason Fung endorses that view. His view is that reducing salt is not necessary except in the case of advanced renal or heart failure. He also says he believes that we are eating about the right amount of salt and cutting it down has not benefits.
“It’s simply a waste of energy,” he says.
Fung says concerns about the health risks of low-salt diets are not new, and one reason for the rosy hue some experts have around the benefits is the common phenomenon known as “confirmation bias”.
Confirmation bias exists in us all , he says, and scientists are no exception.
“You have a certain view of the world, and tend to view all new information through that filter,” says Fung. “It’s like looking at the world through rose-coloured glasses.”
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, he says. After all, it 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 far more important question, says Fung, is the health outcomes of lowering blood pressure. Therein lies the real salty rub.
He says there is no evidence, apart from weak associational studies, to show correlation between salt and life expectancy, or that for most people, a low-salt diet does any good at all. On the contrary, there is strong associational evidence to show that 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.
In a lecture in 2013, available on Youtube, Fung explains a mechanism of action by which salt increases, rather than decreases your risk of dying prematurely from CVD, that includes increasing levels of certain hormones in the body, among them plasma renin,
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 published 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 not wise.
US expert Dr Richard Feinman, professor of cell biology at SUNY (State University of New York) Medical Centre, is similarly dismissive of sweeping recommendation to reduce 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 want 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, Feinman says.
He is not aware of any direct correlation, but “at least we would be talking about who needs to reduce salt”.