Folic Acid Supplements Don't Reduce High-Risk Colon Cancers

Cole said that while the results were surprising, other studies may offer an explanation. "Some of these studies have shown that folate seems to have a dual effect on cancer development. High levels of folate tend to prevent cancer if there's no cancer in the system. On the other hand, other studies suggest that folate may feed undetectable microscopic lesions," he said.

Cole emphasized that this study's findings only apply to people with a history of polyps and not to the population in general.

Cornelia Ulrich, an associate member of the cancer prevention program at the Fred Hutchinson Cancer Research Center in Seattle, said, "This was an important trial that showed clearly there's no benefit from taking folic acid for patients with prior polyps, and possibly, there could be some harm."

Ulrich, who co-wrote an editorial in the same issue of the journal, said she's concerned that people who take supplements, eat fortified foods and eat or drink so-called health drinks or snack bars, may end up consuming as much folic acid as was used in this study.

"People who have had a polyp should carefully review how much additional folic acid they get from health bars and drinks," she said.

And, anyone getting treatment for colon and other cancer should discuss any use of supplements -- folic acid or others -- with their doctor, because they could interfere with their treatment.

Both Cole and Ulrich said the most important step anyone can take for colon cancer prevention is to follow whatever colonoscopy screening schedule their doctor recommends.

More information

To learn more about preventing colorectal cancer, visit the American Cancer Society.

SOURCES: Bernard Cole, Ph.D., associate professor of community and family medicine, Dartmouth Medical School, Hanover, N.H.; Cornelia Ulrich, M.S., Ph.D., associate member, cancer prevention program, Fred Hutchinson Cancer Research Center, Seattle; June 6, 2007,Journal of the American Medical Association