Study: Many men take dietary supplements to prevent prostate cancer

05/06/04

A significant percentage of men take dietary supplements such as vitamins, minerals and herbs to prevent prostate cancer despite a lack of evidence that they work. That is the result of a new study published by Fox Chase Cancer Center researchers in the May issue of the British Journal of Urology International.

"More than half of the men in our study say they take natural products believed to reduce their chances of developing prostate cancer," says Robert G. Uzzo, M.D., a urologic surgeon at Fox Chase Cancer Center and lead author of the study. "Although the preventative effectiveness of many of these supplements is not established, they are widely perceived by the public to lower the risk of developing prostate cancer."

The study evaluated questionnaires given to 333 men upon enrollment into Fox Chase's Prostate Cancer Risk Assessment Program (PRAP). Those eligible for PRAP include African American men and any man with a family history of prostate cancer. The 420-item self-administered questionnaire included questions about the use of nutritional supplements and complementary therapies. Supplemental use was divided into eight categories including vitamins, minerals, and extracts from fruits/seeds, organic compounds, flowers/bulbs, leaves/bark, roots, or animal products.

More than half (51%) of the men who completed the questionnaire reported taking one or more supplements to prevent prostate cancer. Most commonly used were vitamins such as A, B, C, D, and E (95%), minerals such as zinc, calcium and selenium (28%), and fruit/seed extracts such as saw-palmetto, soy isoflavones and flax seed (18%). More than one in four men (27%) took three or more agents.

"The use of vitamin and nutrient supplements for prostate cancer prevention has received a great deal of attention from marketers and the popular media," says Uzzo. "The use of vitamins, minerals and extracts represents a unique cultural phenomenon. The lure of complementary therapies may be in their non-Western nature. That is, their claim to be effective is often based on theories outside of Western medical science."

Currently, researchers at Fox Chase Cancer Center and elsewhere are enrolling volunteers in a nationwide study to determine if the trace mineral selenium and vitamin E, either alone or in combination, can prevent prostate cancer. The study is ongoing and results will not be known for several years.

Uzzo believes the use of supplements outside of a clinical trial is being done so in a complementary role, rather than as a substitute for conventional therapy. He says nutritional supplements are generally felt to be "natural" and therefore, have no side effects when many do.

"Side effects can occur when people take too much selenium, vitamin D or zinc, and there can also be unanticipated interactions with conventional therapies," Uzzo explained. "Other studies suggest that up to 71 percent of patients may not inform their physicians about their use of herbs, so it is important for patients and physicians to talk about the use of herbs in order to avoid potential problems."

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Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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