Vitamin E Supplements May Raise Prostate Cancer Risk
Study Refutes Earlier Suggestion That Vitamin E Lowered Risk of Prostate Cancer
Oct. 11, 2011 -- Just a decade ago, hopes were high that men could lower their risk for prostate cancer by taking daily supplements of the antioxidant vitamin E.
But now, follow-up findings from a study involving 35,000 men offer evidence that the opposite may be true.
Compared to men who did not take vitamin E, those who took 400 international units (IU) of the vitamin every day in the study funded by the National Cancer Institute were 17% more likely to develop prostate cancer over an average of seven years of follow-up.
Researcher Eric A. Klein, MD, of the Cleveland Clinic, says it is unlikely that the association is due to chance.
He adds that taking large doses of vitamin E may be dangerous.
The study, which appears in the Oct. 12 issue of The Journal of the American Medical Association, is not the first to suggest that antioxidant vitamin supplements may promote the cancers that they are intended to prevent.
Earlier studies in smokers found that beta-carotene supplements increased lung cancer risk and the trace mineral selenium has been linked to an increased risk of non-melanoma skin cancer in women and men.
"In the absence of vitamin deficiency, there are no compelling data to indicate that these dietary supplements are beneficial, and some may be harmful," Klein tells WebMD.
Impact of Vitamin E
About 240,000 men in the U.S. will be diagnosed with prostate cancer this year and 33,000 men are projected to die of the disease.
The Selenium and Vitamin E Cancer Prevention Trial (SELECT) began in 2001 to test the theory that taking the antioxidant vitamins reduced the risk of certain cancers.
The 35,533 men in the study -- recruited from the U.S., Puerto Rico, and Canada -- were assigned to one of four treatment groups:
- 200 micrograms of selenium alone daily
- 400 IU of vitamin E
- daily supplementation with both vitamins
- no supplementation (placebo group)
"There has never been a trial of this size and magnitude to examine an intervention to prevent prostate cancer," study co-researcher Laurence H. Baker, DO, of the University of Michigan, tells WebMD.