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Folic Acid May Raise Prostate Cancer Risk

Men Taking High Doses of Folic Acid Supplements More Than Doubled Their Prostate Cancer Risk, Study Shows
WebMD Health News
Reviewed by Louise Chang, MD

March 10, 2009 -- There is mounting evidence that folic acid, taken in high doses, does not protect against cancer and may even promote certain cancers.

Nearly two years ago, a major study found that high doses of folic acid in supplement form failed to protect against colon cancer.

Now, another analysis of the same study's findings suggests a link between folic acid supplements and an increased risk for prostate cancer.

Men in the study who took high doses of the vitamin had a more than twofold increase in prostate cancer risk, compared to men who did not take folic acid supplements.

There were too few prostate cancers among the study participants to prove that folic acid promotes prostate cancer, Jane C. Figueiredo, PhD, of the University of Southern California, Los Angeles tells WebMD.

“What we can say is that a lot of folate is unlikely to be beneficial with regard to prostate cancer, and it just might be harmful,” she says.

Folic Acid and Prostate Cancer

The current study included 643 men originally recruited for a much larger study designed to determine if taking aspirin and a folic acid supplement could reduce the incidence of colon polyps.

The men were randomly assigned to placebo or supplements with daily low-dose aspirin and 1 milligram of folic acid daily -- two and a half times the recommended daily dose of the vitamin for men and for women who are not pregnant or nursing.

Aspirin alone was found to have no significant effect on prostate cancer incidence, but taking folic acid was found to increase the risk for prostate cancer by 163%.

The analysis joins a growing number of studies suggesting that nutritional supplements are of no benefit for preventing cancer.

In an accompanying editorial, two cancer and nutrition experts concluded that “the prospects for cancer prevention through micronutrient supplementation have never looked worse.”

Large trials have shown no protective benefit in people taking multivitamins, selenium, beta-carotene, and vitamins E, C, D, B6, and B12.

Beta-carotene, taken in high doses, has even been shown to promote lung cancers in heavy smokers.

“The primary lesson from our experience in the nutritional prevention of cancer is that it is not simple,” write Alan R. Kristal, MD, of Seattle’s Fred Hutchinson Cancer Research Center and Scott Lippman, MD, of the University of Texas M.D. Anderson Cancer Center.

The study and editorial appear in the March 18 issue of the Journal of the National Cancer Institute.

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