Long-term study confirms salty diet kills

26 April, 2007: Salt is injurious to health and using less salt reduces the chances of suffering a heart attack or stroke, the first long-term study of the impact of salt on health has confirmed.

The findings, drawn from a 15-year study, present the strongest and clearest evidence so far that cutting consumption of does save lives by reducing the risks of cardiovascular diseases.

People who ate less salty food were found to have a 25% lower risk of cardiac arrest or stroke. They also have a 20% lower risk of premature death.

Scientists have concluded that the results of the study, published in the British Medical Journal, stress the need to the need to cut down the amount of salt in the diet.

Despite widespread campaigns to reduce intake of salt, actual evidence of any benefit from them has been limited. Which had emboldened the salt industry to dispute forcefully the worth of such campaigns.

Though both anti-salt campaigners and the salt industry had accepted that cutting salt intake reduced blood pressure – which would in the long term result in decreased strokes and heart attacks – this is the first time a convincing research finding has come out.

The new findings are the result of work by a United Studies team led by Nancy Cook, of Harvard Medical School, which followed up two trials originally conducted in the late 1980s and early 1990s. Both trials had been designed to persuade people to cut their salt intake and to measure how far their blood pressure fell.

By pursuing these trials, the team of Nancy Cook has shown that those who reduced their salt intake did have a lower risk of heart disease and stroke. The research concludes: “Our study provides unique evidence that reduction of sodium might prevent cardiovascular disease and should dispel any residual concern that sodium reduction might be harmful.”

Ellen Mason, cardiac nurse at the British Heart Foundation, reveals that salt intake among many adults and children in Britain is too high. Many people could lower the level of salt in their diet by simply reducing the amount of processed food they eat and by checking the labels and switching to a lower-salt option.

The original studies – called the trials of hypertension prevention (TOHP 1 and 2) – used counselling and advice to persuade participants to reduce intake. In the first trial, 327 healthy men and women aged 30-54, who took part in the intervention, were compared with 417 ‘controls’ who did not.

Measurements of sodium in urine showed that a reduction of roughly one-third in salt intake had been achieved in the 327 who took part, but blood pressure was found to fall only slightly.

The authors of the original study had no idea if this reduction would be sustained, but they estimated that if it were to be sustained, it might reduce stroke deaths by 6%, heart disease deaths by 4%, and deaths from all causes by 3%. However, the follow-up has shown much more noticeable health benefits.

Graham MacGregor, a professor at St George’s University of London, said the size of the benefit was not surprising. When there was a campaign in Finland to cut salt, there was a very large reduction in stroke and heart attacks.

How exactly salt increases blood pressure is still in dispute. The simplest explanation is that when salt intake is too high, the kidneys cannot pass it all into the urine and some of the salt ends up in the bloodstream. This then draws more water into the blood, increasing volume and pressure.

However, scientists conclude that not everybody is equally sensitive to salt, and so not everybody will benefit equally from reducing intake.