Forty years ago, the United States senate undertook the near-impossible task of reviewing all existing evidence on nutrition in order to recommend a diet for optimal health. The result was a set of dietary recommendations that demonised fat, cholesterol and salt, among other nutrients, while trumpeting the benefits of grains. These ‘facts’ became gospel truth for dieters, not just in the US but around the world. It wasn’t until decades later we realised they were wrong.
Since the 1970s, dietary cholesterol has been fully absolved of any blame in the development of heart disease, and dietary fat is fast on its heels. Salt may be next.
But chronically elevated blood pressure, known as hypertension, hasn’t gone away. It’s a serious condition that is strongly linked to deadly conditions like heart attack and stroke, and it affects hundreds of millions of people worldwide. Finding and promoting effective solutions to reduce the prevalence of hypertension would reduce its burden on healthcare systems and improve countless lives. That means continuing with the wrong approach would fail to reduce hypertension deaths and might also obscure other, more effective approaches.
Unfortunately, America may be embracing the wrong approach, as public health agencies focus all their firepower on salt as the cause of and solution to hypertension.
The truth is that people around the world seem to consume a similar amount of salt, but not everyone responds to salt in the same way.
In the US, the average adult consumes about 3,400 milligrams of sodium, and in Britain the average is nearer to 3,100 mg. Both are much higher than the 2,400 mg/day recommended by health authorities.
We are not alone. According to researchers at the University of California, Davis, who analysed data for nearly 70,000 people in 45 different nations, the ‘normal range’ of human sodium intake falls between 2,600 and 4,800 mg a day. Moreover, researchers have repeatedly found that this range has remained stable over the last 50 years, despite increased levels of sodium in processed foods and increased consumption of processed foods.
Meanwhile, not everyone is sensitive to salt. While a minority of people will experience increased blood pressure as a result of high dietary sodium, the majority — upwards of 75 per cent — see no change in blood pressure even at extremely high levels of sodium intake.
Also, for some people, blood pressure actually increases with sodium restriction. And an increasing number of studies shows that as the average level of sodium in a population drops below the recommended level, the risk of death increases.
While this emerging research has certainly fomented debate within the research community’s already divisive debate over salt, it has done nothing to slow the efforts of government and health agencies.
In Britain, the Food Standards Agency set about reducing population sodium intake by educating the public and reducing salt in the food supply. By the government’s account, the effort was a smashing success, resulting in sodium reductions from an average intake level of 3,600 to 3,100 mg per day between 2001 and 2011. However, other researchers who have looked into British sodium consumption dispute any significant change in intake. Either way, the apparent success has spurred other nations to follow suit. In the US, for example, the Food and Drug Administration has proposed a similar ‘voluntary’ sodium reduction plan for food manufacturers.
But now it’s time to stop and ask some critical questions.
First, is it even possible to drive population consumption to below the recommended limit? Britons may have cut 500 mg of sodium from their diets, on average, but they are still well within the normal range of sodium intake observed around the world and still much higher than the recommended limit.
Second, and more importantly, if we could drive average consumption below the recommended maximum would population health really improve? Studies that assert that population sodium reduction plans result in lower rates of heart attacks and strokes are based on fantasies. That is, they are based on the assumption that lower sodium reduces blood pressure and that lower blood pressure reduces disease risk, despite the many studies showing that sodium reduction, for most people, has no effect on blood pressure, does not improve health, and may actually harm health in the majority of the population.
Health agencies have missed more viable solutions to hypertension.
Increased potassium in the diet is proven to lower blood pressure. (Potassium-rich foods, to name just a few, include bananas, avocados, potatoes and spinach.) Unlike sodium restriction, this effect has been observed in populations of varying races, sexes, ages, and even hypertension levels.
A 2003 study, for example, found that increasing potassium by about 1,700 mg a day — the equivalent of two and half cups of cooked spinach — lowered blood pressure almost as much as cutting sodium by 1,700 mg a day. Considering that upwards of 30 per cent of some people in Britain get less than the recommended minimum of potassium, this might seem to be an important aspect of hypertension risk reduction. Yet it has largely been ignored.
In addition to potassium, weight has been conclusively linked to blood pressure. In fact, studies examining the independent effects of both sodium and weight find that reducing weight has a more significant effect on blood pressure than sodium reduction, though together the approaches were even more effective. And the most effective approach tends to involve all three — increased potassium, decreased sodium, and weight loss. What’s more, this combination of approaches may be easier for people to adopt and incorporate into their lifestyles.
When it comes to hypertension, we urgently need real solutions, not a single-ingredient approach that’s been shown not to work.
Michelle Minton is a fellow with the Competitive Enterprise Institute, a free market public policy organisation in Washington, DC.