Folate intake and colorectal cancer risk: a meta-analytical approach.

Adequate consumption of folate may reduce the risk of colorectal cancer. We performed a meta-analysis of 7 cohort and 9 case-control studies that examined the association between folate consumption and colorectal cancer risk. In cohort studies, the association between folate consumption and colorectal cancer risk was stronger for dietary folate (folate from foods alone; relative risk for high vs. low intake = 0.75; 95% CI = 0.64–0.89) than for total folate (folate from foods and supplements; relative risk for high vs. low intake = 0.95; 95% CI = 0.81–1.11) and there was no significant heterogeneity between studies. There was significant heterogeneity between case-control studies. These results offer some support for the hypothesis that folate has a small protective effect against colorectal cancer but confounding by other dietary factors cannot be ruled out. © 2004 Wiley-Liss, Inc.