THOUSANDS of Britons who take daily doses of vitamin E, one of the most popular dietary supplements, are risking premature death, research suggests.

A study has found that the average intake of vitamin E by supplement-users posed a significant increased risk to health.

An estimated one in three women and one in four men in Britain takes dietary supplements to boost their health, but the latest research throws further doubt over the benefits of taking vitamins in high doses.

Vitamin E helps to prevent cell membrane damage and may prevent blood clots and the formation of fatty plaques in the arteries.

But the latest study, by scientists at Johns Hopkins University in Baltimore, reported at a meeting of the American Heart Association, and also published on the website of the Annals of Internal Medicine, found that doses of 400 international units (IU) — often the equivalent of a single capsule — were associated with a 10 per cent increased risk of death.

Researchers studied death rates in published clinical trials, comparing vitamin E supplementation with placebo from the findings of 14 studies since 1993. Doses ranged from 15 to 2000iu a day, and the average intake was about 400iu a day.

Edgar Miller, associate Professor of Medicine at Johns Hopkins and lead author, said that high doses should be avoided. “Increasing doses of vitamin E were linked to an increase in death,” he said.

According to the analysis, there was no increased risk of death with a dose of 200 IU per day or less, and there may even be some benefit.

An increased risk was found at amounts above 200 IU per day and significant risk of death was found starting at 400 IU a day. Those who take more than 400 IU of vitamin E a day are about 10 per cent more likely to die than those who do not, researchers said.

Dr Miller said that many people who took vitamin E supplements were receiving between 400 and 800 IU in a single capsule.

The warning follows numerous studies into vitamin supplements. In animal and observational studies, extra vitamin E was shown to prevent cardiovascular disease and cancer. However, other studies suggested that high doses could be harmful.

The findings also come after a report in The Lancet which estimated that for every million people taking vitamin supplements, 9,000 would die prematurely as a result.

Many health experts suggest that for most of the population who ate a balanced diet, there were no grounds for taking supplements. But they are frequently recommended for pregnant women and the elderly.

Vitamins are anti-oxidant organic nutrients essential for normal metabolism and health. But specialists say there is a difference between the life-long physiological effects of small amounts ingested in the diet from childhood and pharmacological doses taken over a few years by middle-aged adults.

The studies have yet to shown why death rates are increased with high vitamin E intake, although a possible explanation linked to cancer cases is that people may vary in their need for anti-oxidants according to the circulating levels of substances known as free radicals in the blood.

Those with high levels of free radicals need extra vitamins to neutralise them, but in those with low levels, extra vitamins may, paradoxically, protect cancer cells and have carcinogenic effects.

Dr Miller said that daily diets provided between 6 and 10 IU of vitamin E, but intake increased dramatically with supplements.

“Vegetable oils, nuts and green leafy vegetables are the main dietary sources of vitamin E,” he said. “Supplementation can increase intake by a hundred fold.” More research was needed into smaller supplements, which might positively affect death rates, he said.

Last year the Food Standards Agency singled out five substances that may cause permanent damage if taken in large quantities over a long period. They were beta-carotene, which was linked to an increased risk of lung cancer in smokers, manganese (muscle and nerve disorders in older people), nicotinic acid (cell damage), phosphorus (damage to or gans and tissues) and zinc (damage to the immune system).

THE EFFECTS

• Vitamin E is found in vegetable oil, avocados, nuts, leafy vegetables and soya beans
• Recent studies showed that it decreased the risk of a second cardiac arrest in heart attack victims and helped kidney-disease sufferers
• It is also credited with lowering cholesterol, combating menopausal symptoms and reducing the risk of pre-eclampsia
• The recommended daily allowance is 15 IU. A single capsule can contain 400 IU, the level linked with a 10 per cent increased risk of death

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