Chapel Hill, N.C. — A new study suggests that large amounts of folic acid don't prevent the growth of pre-cancerous polyps in the colon, contrary to earlier belief.
Co-authored by Dr. Robert Sandler, a gastroenterologist at the University of North Carolina at Chapel Hill, the study followed about 1,000 people nationwide with polyps for at least three years. Half took a 1-milligram daily supplement of folic acid, while the others took a placebo.
"We were disappointed and surprised to find out that folic acid did not prevent people from developing pre-cancerous tumors of the large bowel," Sandler said. "The risk was increased for certain types of polyps, with worrisome features for people developing more than three polyps.
"I think the take-home message is, if people are taking folic acid to prevent polyps, they should stop because it doesn't work."
The results of the study, which also suggests large daily doses of folic acid might increase the risk of prostate cancer, are published in the latest issue of the Journal of the American Medical Association. Researchers said the link between folic acid and prostate cancer isn't definitive and needs more study.
Despite the findings, Sandler said people should still try to eat the healthy foods that contain folic acid.
"There are certain foods that contain folic acid, like vegetables, leafy vegetables. People should eat those. Those have lots of health benefits," he said. "I think what people should avoid is taking supplements to prevent colon cancer because we've shown that it doesn't work."
Sandler and other health experts said the best way to prevent colon cancer is routine screenings, which can find and remove polyps.
"Colonoscopy is certainly the most effective way to identify colon polyps and colon cancer," said Dr. Doug Robertson, a gastroenterologist at a Veterans Administration hospital in Vermont.