Folic Acid for the Prevention of Colorectal Adenomas

Abstract

Results During the first 3 years, 987 participants (96.7%) underwent colonoscopic follow-up, and the incidence of at least 1 colorectal adenoma was 44.1% for folic acid (n=221) and 42.4% for placebo (n=206) (unadjusted risk ratio (RR), 1.04; 95% con- fidence interval (CI), 0.90-1.20; P=.58). Incidence of at least 1 advanced lesion was 11.4% for folic acid (n=57) and 8.6% for placebo (n=42) (unadjusted RR, 1.32; 95% CI, 0.90-1.92; P=.15). A total of 607 participants (59.5%) underwent a second follow- up, and the incidence of at least 1 colorectal adenoma was 41.9% for folic acid (n=127) and 37.2% for placebo (n=113) (unadjusted RR, 1.13; 95% CI, 0.93-1.37; P=.23); and incidence of at least 1 advanced lesion was 11.6% for folic acid (n=35) and 6.9% for placebo (n=21) (unadjusted RR, 1.67; 95% CI, 1.00-2.80; P=.05). Folic acid was associated with higher risks of having 3 or more adenomas and of noncolorectal can- cers. There was no significant effect modification by sex, age, smoking, alcohol use, body mass index, baseline plasma folate, or aspirin allocation. Conclusions Folic acid at 1 mg/d does not reduce colorectal adenoma risk. Further research is needed to investigate the possibility that folic acid supplementation might increase the risk of colorectal neoplasia. Trial Registration clinicaltrials.gov Identifier: NCT00272324