Folic acid supplementation for the prevention of recurrence of colorectal adenomas: metaanalysis of interventional trials.

Conflicting data have emerged from preclinical and clinical studies that examined the relationship between folic acid and the risk of recurrence of colorectal adenomas. To determine precisely that relation, we planned this metaanalysis. We searched literature to identify interventional randomized, placebo-controlled studies where folic acid in specific dose and for specific duration was administered to evaluate its effect on the recurrence of adenomatous colorectal polyps. Five eligible trials were identified. The total number of patients with history of colorectal adenomas in the folate and the placebo groups was 805 and 775 patients, respectively. Our analysis showed that folate supplementation had no protective effects on the recurrence of colorectal adenomas [odds ratio = 1.08 (95% CI; 0.87, 1.33; P = 0.49)], nor has a positive outcome on the number of recurrent polyps per patient (P = 0.41). Examination of folic acid dose effect showed that the two studies that have used folic acid as 1 mg/day favored folic acid over placebo with an odds ratio of 0.62 (95% CI; 0.48, 0.80). However, the overall effect for all included studies was not significant [odds ratio = 0.78 (95% CI; 0.49, 1.24; P = 0.30)]. We found significant heterogeneity between trials, moreover, included trials exhibit inconsistency in methodological quality. The present metaanalysis has failed to show potential benefit for folate supplementation. Future trials should examine the effect of different dosage and duration. Moreover, the confounding effect of dietary and life style habits should be carefully controlled.