Vitamin E supplements may do more harm than good, and could contribute to some deaths in higher doses, a new review suggests.

Some people take megadoses of the vitamin in the hopes of countering the effects of free radicals, molecules that are thought to damage cells and lead to illnesses such as heart disease or cancer.

Antioxidants like vitamin E act like mops in the body, cleaning up free radicals. But there has been no proof of the health benefits of high doses of vitamins.

Now, researchers at Johns Hopkins University in Baltimore have reanalysed the results of 19 studies on vitamin E involving more than 136,000 patients in North America, Europe and China.

They found an increased risk of death for those taking more than 200 international units of vitamin E a day.

People who took 400 IU daily were 10 per cent more likely to die than if they hadn't take the supplement, the researchers said.

Dose questions

"A lot of people take vitamins because they believe it will benefit their health in the long term and prolong life," said internist Edgar Miller, the study's lead author.

"But our study shows that use of high-dose vitamin E supplements certainly did not prolong life, but was associated with a higher risk of death."

Vitamin E capsules typically contain 400 IU to 800 IU. Dietary guidelines in Canada and the U.S. do not recommend vitamin E supplements, although the upper tolerable limit is set at 1,500 IU per day.

Given the results of the study, policy makers and regulators should consider lowering the limit, said the study's senior author, Dr. Eliseo Guallar, a professor of epidemiology at the Bloomberg School of Public Health.

Many of the patients in the study were over the age of 60 and had health problems like heart disease. The study's findings may not apply to younger, healthier adults, the researchers noted.

Robert Rogers is a herbalist, author and educator in Edmonton, who's worked with supplements for 34 years and believes 400 IU is safe. He said the review is flawed because it only included studies where people died.

More research is needed to show if low doses of vitamin E have protective effects or if they help when combined with other antioxidants, Guallar said.

The researchers speculate high doses of vitamin E may upset the body's natural antioxidant process, or perhaps it interferes with the body's ability to detoxify drugs and toxins. They recommend people talk to their doctor or dietician about using vitamin E.

The research was presented on Wednesday at the Scientific Sessions 2004 meeting of the American Heart Association in New Orleans and appears online in the Annals of Internal Medicine.