Selenium Reduces Risk of Prostate Cancer

Healthnotes Newswire (November 20, 2003)—Men with high selenium intake are less likely to develop prostate cancer than men with low selenium intake, according to a new study published in Cancer Epidemiology, Biomarkers and Prevention (2003:12;866–71).

Selenium is a trace mineral that plays a role in a critical antioxidant pathway in the body. It is also important for normal immune function and might have a direct toxic effect on cancer cells. Selenium is found in wheat germ, Brazil nuts, barley, wheat bran, garlic, and some other grains and vegetables. The exact selenium content of specific foods depends largely on the selenium concentration of the soil in which they grow, making it difficult to assess selenium intake reliably through food questionnaires. Levels of selenium found in toenail clippings have been shown to reflect selenium levels in the blood, which in turn reflect intake.

Prostate cancer is the most common cancer in men in the United States. More than 15% of U.S. men will develop prostate cancer in their lifetimes, and more than 3% will die from it. The incidence is slightly higher in the Netherlands, where the selenium content of foods may differ substantially from those in the U.S. A number of studies performed in the U.S. have found that men with low intake of selenium have a higher risk of prostate cancer than men with high intake of selenium, suggesting that selenium might have a protective role. In addition, one controlled trial found that people given 200 mcg of supplemental selenium per day (in the form of high-selenium yeast) for seven years had a 50% lower risk of death from cancer, including prostate cancer, than people given placebo.

In the current study, 1,733 men in the Netherlands were observed for about six years. Participants answered a dietary questionnaire at the beginning of the study to assess their intake of antioxidants and other nutrients. Selenium levels were measured in toenail clippings, which were collected from participants at the beginning of the study and during each year of follow-up. The risk of developing prostate cancer was found to be 31% lower in men with high toenail selenium levels compared with those whose toenail selenium levels were low. The protective effect of selenium was found to be more pronounced in men whose intake of other antioxidants, especially vitamin C and beta-cryptoxanthin (a carotenoid), was low.

The results of this study are consistent with those of studies performed in the U.S. showing that high selenium intake reduces prostate cancer risk. Interactions between selenium and other antioxidants should be further explored in future studies. Clinical trials to measure the potential preventive effect of selenium supplementation on prostate cancer risk, and to identify optimal amounts, are currently underway.

Maureen Williams, ND, received her bachelor’s degree from the University of Pennsylvania and her Doctorate of Naturopathic Medicine from Bastyr University in Seattle, WA. She has a private practice in Quechee, Vermont, and does extensive work with traditional herbal medicine in Guatemala and Honduras. Dr. Williams is a regular contributor to Healthnotes Newswire.

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