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Mega Multivitamins and Prostate Cancer

Higher Doses Linked to Higher Death Risk
WebMD Health News
Reviewed by Louise Chang, MD

May 15, 2007 -- Men who take too many multivitamins may be increasing their risk of dying from prostate cancer, according to new research from the National Cancer Institute.

Taking a multivitamin more than seven times a week was associated with a 30% increased risk of advanced prostate cancer and a doubling of the risk of death from the disease in the study.

Regular multivitamin use (one to six times a week) did not appear to increase cancer risk, and excessive vitamin use was not associated with an increased risk of early, or localized, prostate cancer.

But there was also no evidence to suggest that taking multivitamins at any dosage helped prevent prostate cancer.

NCI researcher Michael F. Leitzmann, MD, PhD, tells WebMD that more research is needed to confirm the association and understand how vitamin and other dietary supplements affect cancer risk.

“Based on our findings, we would recommend that men adhere to recommendations for dietary supplements and consult with their physician before taking supplements in excessive doses,” he says.

More Questions About Safety

The new research is one of several recent studies suggesting a potential downside to vitamin supplementation in people who are generally well-nourished.

An analysis of 47 studies assessing antioxidant supplementation, published earlier this year, found a slight increase in deaths among people who took beta-carotene, vitamin E, or vitamin A supplements.

Christian Gluud, MD, who co-authored the analysis, tells WebMD that there is little evidence of a benefit for antioxidant supplementation and mounting evidence of potential harm.

“The idea that you can prevent disease by taking an antioxidant supplement is very attractive,” he says. “People want to believe it, and there is a great deal of marketing devoted to making them believe it.”

In the latest study, Leitzmann, co-author Karla Lawson, PhD, and NCI colleagues followed slightly more than 295,000 men enrolled in a diet and health study for five years.

During this time, 8,765 men in the study were diagnosed with localized prostate cancer (cancer that hasn't spread beyond the prostate) and 1,476 with advanced prostate cancer (cancer that has spread beyond the prostate).

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