NEW YORK (Reuters Health) — Daily use of folic acid supplements does not prevent colon adenomas in patients with a history of these growths, which usually develop into cancer over time, according to a report in the Journal of the American Medical Association.In fact, there was some indication that folic acid supplementation may increase the risk of advanced adenomas.

The results of animal research regarding folic acid have been inconsistent, note lead author Dr. Bernard F. Cole and associates. Folic acid may have a dual effect, protecting normal colon tissue and enhancing the growth of abnormal tissue, they suggest. To better understand the effects of folic acid, Cole, of the Dartmouth-Hitchcock Medical Center in Lebanon, New Hampshire, and his team assessed the occurrence of adenomas in 1,021 subjects who were randomly selected to use folic acid or inactive “placebo” pills daily for several years. All of the subjects had one or more adenomas removed via colonoscopy in the past.

During follow-up, the percentage of patients in each group who developed at least one adenoma was comparable, about 40 percent. Patients given folic acid, however, had a higher rate of advanced adenomas: 11.6 vs. 6.9 percent.

Editorialists at the Fred Hutchinson Cancer Research Center in Seattle hypothesise that undetected pre-cancerous tumors were still present in these patients and that folic acid promoted their growth.