Take the fluctuating diktats of nutritionists with a good pinch of salt.

Several specific government food targets — however well intentioned — contain a modicum of guesswork, claims this article from the Sunday Times. “Five-a-day, 14-21 alcohol units a week, 20-30g of saturated fat, 18g of fibre: none of these targets has any precise evidence for them,” Zoë Harcombe, who co-authored last week’s study, has written.

The less salt that we eat in our diet, the harder our kidneys have to work to reabsorb it

One of the most staunchly held truisms of modern nutrition is that salt is bad for you. “Salt: the facts”, begins a taxpayer-funded website. “Many of us in the UK eat too much salt,” it affirms. “Too much salt can raise your blood pressure, which puts you at increased risk of health problems such as heart disease and stroke . . . Cutting down on salt lowers blood pressure.” It adds that we should eat “no more than 6g of salt per day”.

“Why six?” asks Harcombe. “I have no idea and nor does the NHS. Why not seven? Why not five? Why have a target at all?”

The evidence that salt causes high blood pressure is decidedly shaky and has been repeatedly called into doubt. It rests for the most part on a couple of not especially recent or thorough trials. In the 1970s a Long Island scientist induced high blood pressure in rats by feeding them sodium that equated to a human eating 2,500g of salt a day. (Most of us eat around 8.5g of salt a day, or about 1½ teaspoons.)

salt shaker

In 1997 another study was held, ostensibly looking into whether a low-salt diet could control high blood pressure. Its participants followed a diet that not only featured minimal salt, but also contained fresh vegetables and fruits, lean protein and whole grains; it was low in saturated fat and, perhaps most crucially, contained little sugar.

Unsurprisingly, rates of high blood pressure in the group were lower than in the general population. But a lack of salt could not be isolated as the reason behind this. More than that, the low-salt group had higher rates of bad cholesterol, leading some researchers to call the results “one-sided”.

Avocados contain about 25g of fat, which led people to shun them in the 1980s. Now they are thought to raise good cholesterol. And have you ever met someone who got fat from avocado?

avacado

In contrast, the evidence that salt has a negligible effect on blood pressure — at least in most people — is now considerable. In January an international study, which followed more than 150,000 people across five continents, found that consuming less than 3g of sodium a day — or about 7.5g of salt — was associated with a 27% increase in cardiovascular disease and death. Eating between 3g and 6g of sodium, which is roughly the amount we normally eat, was associated with a lower rate of heart disease, while consuming more than 7g (about 18g of salt, or almost three times the UK average) was associated with a higher risk of heart disease and death.

This study has been buttressed by at least 10 others during the past 30 years, collectively following hundreds of thousands of people. One from 2011, which followed almost 4,000 Europeans for eight years, found that the risk for heart disease was 56% higher in a low-salt group than among those who ate the most salt.

These studies have repeatedly found that low-sodium diets — the same that you are exhorted to follow when you read websites such as “Salt: the facts” — could be more likely to kill you than simply eating the amount of salt that tastes right. We seek out foods that contain salt because without it we die.

“Restricting sodium in the diet to prevent hypertension and cardiovascular disease is the greatest con in preventative nutrition and medicine,” says James DiNicolantonio, a cardiovascular research scientist and an associate editor of the British Medical Journal’s online publication Open Heart. “Among people who lower their salt intake, the same percentage who get a reduction in blood pressure also get an increase in it.”

The rise of low-carb diets, including Atkins, led to people rejecting the first food of civilisation. But sourdough bread in particular is full of iron, zinc and magnesium, antioxidants, folic acid and other B vitamins. One study found it was safe for gluten-intolerant people.

He adds: “Low sodium stresses the heart. This increases the risk of atherosclerosis, heart failure and hypertension: the exact conditions that most governments and health institutes are trying to prevent by promoting low-salt intake for everyone.”

DiNicolantonio points out that our brains drive sodium intake: “That is one reason [why], over the past 50 years across diverse populations, consumption has been in a such a narrow range.

“In Britain, sodium intake has only fallen about 10-15% during the past decade. The authorities are shooting for 50% — a figure that would likely induce harm. Restricting sodium is also associated with increased mortality, worsened cognition and gait, increased risk of falling and subsequent fractures and worsened thyroid function — just to name a few.”

Despite decades of instructions exhorting people to cut down on the amount of salt they eat, the actual rates of salt consumption in developed countries are thought to have been relatively stable since the Industrial Revolution. Put simply: people are ignoring the advice not to eat more salt.

In part, this is because about 80% of the salt we eat in Britain comes from processed foods: cereals, frozen ready meals, pies, supermarket pizzas and so on. Barely a fifth is added in cooking or at the table. If salt caused high blood pressure, the past 30 years would have seen a spike in salt consumption. They have not. What we have seen instead is a surge in the consumption of refined carbohydrates and, especially, sugar.

DiNicolantonio points out that telling the food industry to lower the salt in processed foods may mean that people eat more of those foods to get the salt their physiology demands.

“So low-salt policies may lead to increased consumption of processed foods and the added sugars they bring with them,” he says, “which might in turn lead to increased type 2 diabetes, cardiovascular events and chronic metabolic disease.”

Sonia Pombo is a campaign co-ordinator and a graduate in nutrition who works at the Consensus Action on Salt and Health pressure group. She says those studies that fail to show a link between blood pressure and sodium are “limited and methodologically flawed”.

She adds: “It is evident that salt, in the amounts we eat, is a direct toxin that puts up our blood pressure, which is the biggest cause of strokes, heart attacks and heart failure and is the commonest cause of death and disability in the UK.”

Olive oil contains six times the saturated fat of pork, and is less chemically stable than butter and lard, which are therefore better for cooking.

olive oil

“A ‘direct toxin’?” says DiNicolantonio. “Salt is an essential micronutrient that our body can retain or excrete to maintain the perfect amount. The less sodium we eat, the harder our kidneys have to work to reabsorb it.”

I ask Harcombe whether, after butter and possibly salt, any other foods might be ready for rehabilitation.

“Eggs, certainly,” she says. “The evidence shows that eating cholesterol has no effect on the cholesterol in our own bodies — the American guidelines were just updated to reflect that. And eggs are high in cholesterol because a healthy chicken — or, indeed, a human — needs it to survive. Egg farmers went out of business because of that flawed advice, while cereal manufacturers made huge profits.”

Harcombe also believes that milk, lard and red meat are due to come back into favour. “The media often lump red meat with processed meat as equally likely to cause bowel cancer. The former is one of the most nutritious things on the planet: the latter is probably toxic,” she says.

The message to take from this dispiriting tale will be familiar. It is to eat fresh and wholesome food: vegetables, fruit, whole grains and nuts. Enjoy meat, fish and animal fats as accompaniments rather than as the basis of a dish. Don’t overdo sugar, but remember that food is as much about pleasure and the communion of the species as it is about fuel. Above all else, take the fluctuating diktats of nutritionists and killjoys with the best seasoning of all — a good pinch of salt.