TUESDAY, Oct. 11 (HealthDay News) -- Men taking supplemental vitamin E may be increasing their risk for prostate cancer by up to 17 percent, a new study suggests. But the reason for the association is unclear, the researchers say.
"Practically, this means for every 1,000 men who take vitamin E, 76 men get cancer, compared with 65 if they were taking placebo," said lead researcher Dr. Eric A. Klein, chairman of the Glickman Urological and Kidney Institute at the Cleveland Clinic.
The new finding comes on the heels of a study released Monday that found that dietary supplements -- including multivitamins, which often contain vitamin E -- are associated with worse health in older women.
Why vitamin E might increase the risk for prostate cancer isn't known, Klein said. "There's a biologic implication here we don't understand. But what it suggests is that vitamins can potentially be harmful," he said.
The study is published in the Oct. 12 issue of the Journal of the American Medical Association.
For the study, Klein's team looked at whether vitamin E or selenium -- a mineral supplement -- increased the risk of prostate cancer among men who took part in the Selenium and Vitamin E Cancer Prevention Trial (SELECT).
In 2008, initial reports from the trial found neither vitamin E nor selenium reduced the risk of prostate cancer. Instead, there appeared to be an increased, although insignificant, risk tied to vitamin E.
The updated finding was based on an analysis of nearly 35,000 men randomly assigned to receive selenium (200 micrograms/day), vitamin E (400 IU/day), both supplements or a placebo for 5.5 years. The men were followed through July 5, 2011.
Since the 2008 report, another 521 cases of prostate cancer were diagnosed. Of these 113 were among men taking the placebo, 147 taking vitamin E, 143 taking selenium and 118 taking both supplements
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