Folic acid (a B vitamin) may have a protective effect against colorectal cancer. A new double-blind, placebo-controlled study, published in Cancer Epidemiology, Biomarkers & Prevention (Vol. 16, Number 10, 2007; Pages 2128-2135) looked at the combination of folic acid and riboflavin (which is vitamin B2) and the effect on colorectal polyps. The subjects of the study were 106 patients with polyps and 98 healthy people. The subjects were randomized to receive either a placebo, 1200 mcg of folic acid per day, 400 mcg of folic acid, or 400 mcg of folic acid with 5 mg of riboflavin per day.

The researchers looked at a reduced form of called 5-methyltetrhydrofolate (MTHF), measuring it in colon tissue. Taking folic acid increased MTHF in a dose-dependent manner. Folic acid supplementation also increased MTHF in red blood cells and in plasma.Taking a combination of folic acid and riboflavin further increased the red blood cell and plasma MTHF in the subjects with polyps, but not in healthy controls.