Folic acid may not do anything to decrease the risk of benign colorectal tumours; in fact new research in the Journal of the American Medical Association suggests it may increase the risk for some types of colorectal tumours.
Folic acid is a synthetic form of folate, a B vitamin found in leafy vegetables, citrus fruit and beans. It is needed for the production of red blood cells and is recommended for women planning to become pregnant because it prevents many birth defects.
Some previous studies have suggested that folate supplementation may help to prevent colorectal tumours; the researchers expected to find similar results this time.
Bernard F. Cole, Ph.D., of Dartmouth Medical School in New Hampshire, and colleagues evaluated the effect of folate for the prevention of new colorectal adenomas -- benign tumours that are the precursors of most colorectal cancers -- in people with a history of these types of lesions.
The study was conducted at nine clinics in the U.S. and Canada between July 1994 and October 2004 and included 1,021 men and women with a recent history of colorectal adenomas but no previous large intestine cancerous tumor.
Participants were randomly assigned to receive 1 mg/day of folic acid or placebo, and were separately randomized to receive aspirin (81 or 325 mg/day) or placebo. They then had two colonoscopies over the next five years.
Contrary to what the researchers expected, more benign tumours were found in people who received folic acid.
In the first follow-up interval, benign tumours occurred in 42.4 per cent of the participants in the placebo group and 44.1 per cent of the participants in the folic acid group. In the second follow-up interval, benign tumours occurred in 37.2 per cent of the participants in the placebo group and 41.9 per cent of the participants in the folic acid group.
The authors say further study is needed - particularly since many foods in the U.S. food supply are required to be fortified with folic acid.
An accompanying editorial suggests that a possible explanation for the study's findings is that many of the subjects may have already had undetected early-stage lesions, and folic acid promoted the growth of these lesions.
"The question of efficacy of folate in cancer prevention is not resolved, and animal experiments showing chemopreventive effects of folate, as well as the strong observational epidemiological evidence, speak to the potential of folate as a chemopreventive agent, if taken early," the commentary reads.
