Folic Acid Supplements Raise Prostate Cancer Risk

Mar. 11 -- TUESDAY, March 10 (HealthDay News) -- A 10-year study has found that men who took folic acid supplements faced more than twice the risk of prostate cancer as those who didn't take the supplements.

But the incidence of prostate cancer in the study was slightly lower in men who simply got adequate amounts of folate in their diet, according to a report in the March 10 online issue of the Journal of the National Cancer Institute.

"What we think is that perhaps too much folate is not necessarily beneficial, whereas adequate levels may be," said study leader Jan Figueiredo, an assistant professor of preventive medicine at the University of Southern California.

Folic acid is a synthetic version of folate, a basic nutrient found in green, leafy vegetables. In the study, which followed 643 men for slightly more than a decade, the estimated prostate cancer risk was 9.7 percent for the men who took the daily 1-milligram supplements, and 3.3 percent for men who took a placebo.

"Folate plays an important role in cell growth and division, and cancer cells often uprate their folate receptors," Figueiredo noted. "Folic acid, the synthetic version, has more bioavailability, meaning that the effective dose in the cell is higher than what you get from natural sources."

Dietary sources of folic acid in the United States now include cereals and other grain products. The U.S. Food and Drug Administration has required folic acid enrichment of those foods since 1996, in part to reduce the incidence of birth defects affecting development of the central nervous system.

"Since we fortified, the amount of folate we consume from fortified foods is probably more than sufficient," Figueiredo said.

The newly reported results resemble those of a study done several years ago by Victoria Stevens, strategic director of laboratory services at the American Cancer Society, who specializes in research on folate metabolism.

That study of folate intake and prostate cancer "found that it really didn't have much effect," Stevens said. "Our study actually suggested that folate might be protective for men with advanced prostate cancer, a group that wasn't included in this study."