Folic Acid May Raise Prostate Cancer Risk
Men Taking High Doses of Folic Acid Supplements More Than Doubled Their Prostate Cancer Risk, Study Shows
March 10, 2009 -- There is mounting evidence that folic acid, taken in high
doses, does not protect against cancer and may even promote certain
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
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.
Popping Pills Doesn’t Work
Kristal and Lippman write that it made sense to study single micronutrients
early on because numerous studies had found that eating a healthy diet with
plenty of micronutrient-rich fruits and vegetables can help protect against
But it is increasingly clear that if the foods we eat influence our cancer
risk, the relationship is too complex to break down to single nutrients.