Stay away from the white stuff. Once you start, you’ll be hooked. It will ruin your life and may eventually kill you. And children, in particular, must be saved from its seductive grip.

This was the message issued recently by scientists, in an effort to persuade the UK to reduce its salt intake.

Table salt, or sodium chloride, raises blood pressure. High blood pressure (hypertension), although symptomless, is a known risk factor for stroke and coronary heart disease. Britons consume 9.5 grams of salt per day, and we should aim to eat less than 6 grams, equivalent to a teaspoon.

The UK government estimates that cutting salt intake by a third would, on average, lead to a 13 per cent drop in the incidence of stroke and 10 per cent fewer cases of heart disease. That could save around 35,000 lives.

Dr Susan Jebb, head of nutrition and health research for the Medical Research Council nutrition centre in Cambridge, wrote the MRC’s report on salt, which was launched at a press conference in London earlier this month. It supports the government’s message that cutting salt intake can reduce blood pressure and improve the health of the nation: “Among independent scientists, there is a clear consensus on the evidence of the link between health and blood pressure,” Jebb declared.

At the press conference, Jebb, who has young children, confessed to giving up crisps and becoming fastidious about reading food labels.

Jebb, who was joined by Paul Lincoln, the National Heart Forum, and Prof. Peter Aggett, the University of Central Lancashire and a government adviser on salt, was tackling one of the most contentious disputes in public health: the link between salt and sickness.

Salt has long tumbled from its historic pedestal as an expensive delicacy and our consumption of it is now a matter of national concern. While the evidence that high blood pressure is a factor for stroke and heart attacks is firm, the corresponding evidence that cutting salt reduces blood pressure enough to ward off a heart attack is more equivocal.

On one side, salt producers ? worried about their product becoming as stigmatised as tobacco ? reject the suggestion that the path to a hospital bed is sprinkled with salt. On the other, public health watchdogs maintain that any reduction in the nation’s blood pressure, however small, is worth striving for.

Last year, when the UK government launched a ?4 million advertising campaign to curb national salt intake, the UK-based Salt Manufacturers’ Association claimed that it was based on questionable evidence, and that alcohol and obesity were equivalent risk factors for high blood pressure.

Prof. Graham MacGregor, chairman of the lobby group Consensus Action on Salt and Health, and a consultant at St George’s Hospital, London, countered this by saying that “if successful it will result in the biggest improvement in public health since the introduction of clean water and drains into the UK in the late 19th century.”

Salt is 40 per cent sodium and 60 per cent chloride; it is the sodium that poses a health issue. The human body requires a tiny amount to help nerves and muscles to function; the element also regulates fluid in the body. A daily intake of 1 gram of salt is enough to meet this biological need (the 6 grams recommendation, while still high, is seen as an achievable objective). Nonetheless, Britons get through nearly 10 grams a day, and a fifth of men ? keen consumers of processed meat products ? consume more than 15 grams daily. Crisps, one of the saltiest foodstuffs at around 1 gram a bag, are a national weakness.

In most people, excess sodium is flushed out by the kidneys and excreted in urine. But for those whose kidneys cannot cope, the extra sodium trapped in the body draws out water from the body’s tissues. The heart works harder to pump the extra fluid, and blood pressure rises. One in three Britons suffers from hypertension, defined as a blood pressure that is persistently above 140/90 mm of mercury.

Researchers have worked hard to isolate and quantify the link between sodium and disease. A recent survey of 23,000 people in Norfolk suggested that those with the saltiest diets were twice as likely to develop hypertension as those on the least salty diets.

In public health terms, the question is whether cutting salt reduces blood pressure, and whether those reductions lead to a measurable reduction in disease. The trend is clear ? the lower the salt intake of a population, the lower the average blood pressure will be.

The salt lobby’s argument is that the benefits gained by salt reduction are so small as to be of questional clinical relevance. The Salt Manufacturers’ Association states: “Scientific research shows that lower sodium diets have a minuscule long-term effect on the blood pressure of healthy individuals.”

Almost everyone else, though ? the Food Standards Agency (the government’s food watchdog), plus the majority of doctors, scientists and nutritionists ? recommend the precautionary principle. As the MRC report summarises: “Since individuals will not be aware of whether or not they are salt-sensitive, and since there are no advantages to a high salt intake, it follows that the greatest benefits will be achieved by encouraging the whole population to decrease the average intake of salt.”

Common ingredient: A Japanese sumo wrestler throws salt to purify the ring

Since 60-75 per cent of salt in our diets comes from bought staples such as bread, cereals, soups, processed meats, cheeses and biscuits, the risk of consuming too little salt seems remote. Salt that occurs naturally in foods ? such as milk ? accounts for 15 per cent. That leaves only another 10-15 per cent that is added during cooking or at the table.

The UK Department of Health now has the food industry in its sights. Last year, it “named and shamed” food companies for failing to cut salt in foods such as bread and cereals (it is added for flavour, texture and as a preservative). Shortly afterwards, the Food and Drink Federation announced that salt in sliced bread would be cut by 5 per cent (one slice contains about 0.5 gram), and salt in cereals would be cut by 9 per cent (a bowl of corn flakes contains about 1 gram).

MacGregor has denounced such changes as “fiddling at the edges”. The two warring sides have reached an impasse ? while campaigners clamour for steeper cuts, manufacturers protest that unpalatable low-salt foods will force British consumers to buy salt-laden imports.

Manufacturers are being urged to clean up their act in other ways, such as providing large-print, front-of-packaging information, and replacing “sodium” content with “salt” content ? many consumers are unaware that “sodium” values must be multiplied by 2.5 to calculate salt content.

Lo-Salt, which replaces the sodium in salt with potassium, is better for health. We are, though, being encouraged to re-educate our tastebuds so that we crave neither salt nor salt substitutes, prompting an increased consumer demand for low-salt products.

Doctors advise giving up crisps, eating less cereal, bread, bacon and pizza, fewer ready-made desserts, and eating smaller portions of salty foods such as cheeses and hams.

The FSA has devised a “salt--meter”, which lists the salt contents of common foods.

THE TIMES, LONDON