Pooled analyses of 13 prospective cohort studies on folate intake and colon cancer

Studies of folate intake and colorectal cancer risk have been inconsistent. We examined the relation with colon cancer risk in a series of 13 prospective studies. Study- and sex-specific relative risks (RRs) were estimated from the primary data using Cox proportional hazards models and then pooled using a random-effects model. Among 725,134 participants, 5,720 incident colon cancers were diagnosed during follow-up. The pooled multivariate RRs (95% confidence interval [CI]) comparing the highest vs. lowest quintile of intake were 0.92 (95% CI 0.84-1.00, p-value, test for between-studies heterogeneity = 0.85) for dietary folate and 0.85 (95% CI 0.77-0.95, p-value, test for between-studies heterogeneity = 0.42) for total folate. Results for total folate intake were similar in analyses using absolute intake cutpoints (pooled multivariate RR = 0.87, 95% CI 0.78-0.98, comparing a parts per thousand yen560 mcg/days vs. < 240 mcg/days, p-value, test for trend = 0.009). When analyzed as a continuous variable, a 2% risk reduction (95% CI 0-3%) was estimated for every 100 mu g/day increase in total folate intake. These data support the hypothesis that higher folate intake is modestly associated with reduced risk of colon cancer.