Vitamin E may raise prostate cancer risk

A study that followed up on men who took high doses of the vitamin E for about five years found they had a slightly increased risk of prostate cancer, even after they quit taking the pills.

Doctors say it's another sign that people should be careful about using vitamins and other supplements. Taking too much vitamin E may be harmful, a U.S. researcher says.

"People tend to think of vitamins as innocuous substances, almost like chicken soup — take a little and it can't hurt," said lead author Dr. Eric Klein of the Cleveland Clinic. The study shows that is not true.

"If you have normal levels, the vitamin is probably of no benefit, and if you take too much, you can be harmed," Klein said.

Men randomly assigned to take a 400-unit capsule of vitamin E every day for about five years were 17 per cent more likely to get prostate cancer than those given dummy pills. That dose, commonly found in over-the-counter supplements, is almost 20 times higher than the recommended adult amount, which is about 23 units daily.

The results mean for every 1,000 men who took vitamin E, there were 11 additional cases of prostate cancer, compared with men taking dummy pills.

The study was actually launched to try to confirm less rigorous research suggesting vitamin E might protect against prostate cancer.

Overall, about 160 of every 1,000 U.S. men will develop prostate cancer in their lifetime.

Risks increase as men age. Detection can be tricky since symptoms such as frequent urination can also be caused by harmless conditions, and doctors disagree about the benefits of screening tests. Treatment is also complex since some slow-growing prostate cancers are not deadly but some procedures, including surgery, can damage sexual function and cause incontinence.

Just last week, a U.S. government-convened panel of experts recommended against routine PSA screening for prostate cancer. That draft advice is open for public comment.

What should vitamin E users do, given the new study results?

About 13 per cent of American men take it, according to a supplement trade group.

Dr. Otis Brawley, chief medical officer for the American Cancer Society, says they should stop taking large doses and talk to their doctors about risks and benefits from prostate cancer screening. Smaller doses, typically found in multivitamins, are probably fine, said Brawley, who was not involved in the research.

Vitamin E is found in foods such as nuts, seeds and vegetable oils. The nutrient helps nerves, muscles, blood vessels and the immune system function.

Vitamin E supplements have long been promoted for disease prevention, but scientific research has disproven many claims and suggested they might increase risks for some conditions, including heart failure.