Introduction Several case-control studies have suggested inverse associations between whole grain intake and colorectal cancer risk, but few cohort studies have been published on the subject. As part of the Continuous Update Project of the World Cancer Research Fund we conducted a systematic review and meta-analysis of whole grain intake and colorectal cancer risk.

Methods We searched the Pubmed database for prospective cohort and nested case-control studies of whole grain intake and risk of incident colorectal cancer, up to December 2010. Summary RRs were calculated using a random effects model.

Results Seven cohort studies reported results for total whole grain intake and colorectal cancer risk. The summary RR for high vs low intake of whole grain was 0.79 (95% CI 0.72 to 0.86), with no significant heterogeneity, I²=0%. The summary RR for a 3 servings per day increment was 0.81 (95% CI 0.75 to 0.88), with little heterogeneity, I²=15%. A similar reduction in risk was also found for colon cancer (summary RR=0.81, 95% CI 0.70 to 0.95, I²=0%), but the result for rectal cancer was not statistically significant and there was substantial heterogeneity (summary RR=0.75, 95% CI 0.53 to 1.08, I²=87%).

Conclusion Our results support the hypothesis that whole grain consumption protects against colorectal cancer.