By Marika Sboros
Are you eating too much salt? Heart foundations and dietitians’ associations globally say that you are. They have practically hardwired advice to eat less salt into people who worry about their heart health.
Other experts – including scientists at Harvard Medical School and the World Health Organisation (WHO) – say the same thing. They say that a low-sodium diet protects your heart and blood vessels. They also say that it prevents premature death from cardiovascular disease (CVD – heart attack and stroke).
Yet some medical experts have said the opposite for years. They say that far from being cardio-protective, a low-sodium diet actually increases your CVD risk. They also say that going after salt targets the “wrong crystal”. And, they say that sugar is far more of a risk than salt to heart and overall health.
Official daily targets
Salt is also called sodium chloride and food labels may often only give the sodium figure. To work out how much salt that is, simply multiply the sodium figure by 2.5.
Current WHO guidelines set daily dietary sodium targets between 1,500 and 2,300 milligrams. That’s well below the average US daily consumption of about 3,400 milligrams. The American Heart Association and other heart foundations globally follow the WHO guidelines.
In the UK, authorities recommend that adults should eat no more than 6g of salt. That’s 2.4g of sodium daily. In 2014, the average salt consumption for UK adults in 2014 was a hefty 8g a day.
Many doctors and dietitians who advise a low salt intake also advise following official dietary guidelines. In particular, they recommend the DASH diet. That’s short for the low-sodium Dietary Approaches to Stop Hypertension diet. The diet is high in fruits, vegetables and whole grains and moderately high in nuts and low-fat dairy products. It is also low in red and processed meats.
But is there really any science behind low-salt advice? That depends on who you talk to.
In South Africa, the Heart and Stroke Foundation of SA (HSFSA) favours a low-salt approach. It has based its advice on “the totality of evidence to date”, says CEO Dr Vash Mungal-Singh. She claims that the evidence supports “the link between excess sodium consumption, hypertension and cardiovascular endpoints”. One of those “end-points” is premature death.
However, Mungal-Singh agrees that too little salt can be bad for health. But the real problem, she says, is overconsumption, especially among South Africans.
To that end, the HSFSA has partnered with food giant Unilever to create a new “salt calculator”. Most people eat mostly highly processed foods that contain hidden salt, Mungal-Singh says. Thus, they don’t realise just how much they are consuming.
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 (NCDs).
The Association for Dietetics in South Africa (ADSA) is among dietitians’ groups globally that support salt reduction for health and financial benefits. ADSA says that salt reduction (only in bread, margarine, gravy and soup) in South Africa could result in 7400 fewer cardiovascular disease deaths. It could also lead to 4300 fewer non-fatal strokes per year and potential cost savings of up to R300-million.
A pinch of salt needed?
Experts on the other side of this scientific fence, including cardiologists, want you to take all that with a pinch of salt.
They say that conventional “wisdom” on salt reduction to prevent CVD and other health problems is unwise. They say that the totality of scientific evidence isn’t there to support less morbidity or mortality from eating less salt.
These experts have fewer ties to food and pharmaceutical companies compared to doctors and dietitians who promote low-sodium diets. They also do not promote the influential US official dietary guidelines. They say that the science behind the guidelines is lacking.
For more on that, read US investigative writer Nina Teicholz’s report in the BMJ last year. In it, she poses the question: The scientific report guiding the US dietary guidelines: is it scientific?
Also, read an 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 on salt reduction.
Another specialist who is scathing of the “wisdom” of a low-sodium diet is US cardiovascular research scientist Dr James DiNicolantonio. DiNicolantonio, of Saint Luke’s Mid America Heart Institute, says that experts who promote salt reduction programs are going after the “wrong white crystals”. In a study in the BMJ Open Heart in 2014, he says that sugar is a more important cause of hypertension and cardiometabolic disease.
Low-salt a ‘waste of energy’?
Canadian nephrologist (kidney specialist) Dr Jason Fung endorses that view. He says that reducing salt is mostly unnecessary except in the case of advanced renal or heart failure.
Restricting salt is” simply a waste of energy,” he says.
Fung says that concerns about the health risks of low-sodium diets are not new. He identifies “confirmation bias” as a reason that so many experts promote salt reduction.
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.”
A low-salt diet can lower blood pressure. However, the far more important question is the health outcomes of lowering blood pressure, says Fung. Therein lies the real salty rub.
He says that there is no evidence, apart from weak associational studies, to show correlation between salt and life expectancy. In other words, for most people, a low-salt diet does little to no good at all. On the other hand, strong associational evidence shows that a low-salt diet can be actively bad. And the less salt you eat, the higher your risk of CVD and other serious health problems.
In a lecture in 2013, available on Youtube, Fung explains a mechanism of action by which too little salt intake increases your CVD risk. One way is that it increases levels of certain hormones, plasma renin among them.
No reduced CVD risk …
Fung refers to the 2013 report from the US Institute of Medicine that advises Congress on health issues. The report found no evidence that cutting sodium intake below the recommended 2,300 milligrams reduced CVD risk
As well, 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. It showed that those eating less than 3,000 milligrams of sodium a day had a 27% higher risk of death or a serious CVD event than those who ate more.
The study also showed that risk of death or other major events increased with sodium intake above 6,000 milligrams.
These findings build on a vast body of research to show that aggressively low sodium targets are not wise.
US cellular biologist Dr Richard Feinman is similarly dismissive of sweeping recommendations to reduce sodium. “If the recommendations are meaningful there should be almost unanimous agreement, whereas there is widespread disagreement,” Feinman says.
If experts really wanted to recommend general advice for people, it should be to get their blood pressure tested, he says. That way, “at least we’d be talking about who really needs to reduce salt”.