Folic acid and cancer links—what should you do?

Recent research has raised the unsettling possibility that too much folic acid might increase the risk of colon cancer. That’s scary, since obstetricians tell pregnant women to take supplemental folic acid to prevent birth defects, and food manufacturers now add the vitamin to flour, pasta, cereals, and other enriched-grain products. Does that mean you should throw away those pills and avoid those foods?

No. And here’s why.

In one of the worrisome studies, of 607 people with a history of precancerous polyps, 30 volunteers who took 1,000 micrograms of folic acid every day for five years developed multiple new growths, compared with 13 of those who took a placebo. And a recent observational study found that rates of colorectal cancer began to rise in the late 1990s, about the same time manufacturers started fortifying enriched grains with folic acid.

While those findings raise some cautionary flags, our medical consultants say it is too soon to give up on folic acid. Considerable previous research suggests that folic acid helps prevent cancer, including colon cancer. And many causes, such as changes in dietary or exercise patterns, could contribute to the increase in colon cancer incidence seen in the observational study. Even if folic acid does promote colon cancer, that risk may be limited to high doses or people who already have cancerous growths.

Women who are pregnant or thinking about becoming so should still take prenatal vitamins containing folic acid, since the vitamin’s proved benefits against birth defects greatly outweigh any possible colon-cancer risks. And the evidence isn’t strong enough to justify avoiding enriched grains. But you may want to pass on supplements with high doses of folic acid, especially if you have a history of colon polyps or cancer. Instead, aim to eat foods naturally rich in folic acid, including beans, leafy green vegetables, citrus fruits, and whole grains.   

This article first appeared in the February 2008 issue of Consumer Reports on Health.

Comments

[clive collins]

"But you may want to pass on supplements with high doses of folic acid . . ." In articles of this nature, it would be helpful to not use general terms like "high" and instead cite an amount like "800 Grams, 12 pints, etc.", or whatever. What is "High" anyway? Keep up the good work. Clive

[Rexall Ranger]

Please cite the actual medical journal name, yr, vol, page # for the study in question....Evidence-based medicine is important, testimonials should not be included.