Taking Vitamin E Puts Men at Greater Risk for Prostate Cancer, Study Finds

"If the Select trial findings were all we had, my concern might be a little higher," Byers said. "But I view this finding as contributing to an overall pattern showing little or no association [between vitamin E and prostate cancer] rather than to an overall conclusion of proven harm."

For now, experts say men shouldn't take vitamin E with the hope that it will prevent prostate cancer, and many question whether loading up on extra vitamin E is a good idea at all.

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"Except for cases of clear deficiency, supplementation of vitamin E has not been shown to benefit any aspect of health, so there is no rationale for taking it," said Jack Cuzick, head of the Centre for Epidemiology, Mathematics and Statistics at the Wolfson Institute of Preventive Medicine in London.

For people who do want to take vitamin E, Minasian said getting the proper dose is the key. Men in the Select trial took a high dose of 400 IU; the Food and Nutrition Board at the Institute of Medicine recommends a daily intake of just 33 IU of vitamin E. Minasian said consumers buying supplements should check the labels and be sure the vitamin dose isn't excessive.

And it is possible to get vitamin E in foods like certain oils, meats, eggs, and leafy vegetables.

"Most people in this country, if they have a well-balanced diet, get the needed amount of vitamin E," Minasian said. "It goes back to what your grandmother said -- moderation in everything."