Colorectal adenomas and the C677T MTHFR polymorphism: evidence for gene-environment interaction? Cancer Epidemiol

5,10-Methylene-tetrahydrofolate reductase (MTHFR), an enzyme in folate metabolism, may play a role in the etiology of colorectal adenomas via effects on DNA methylation and nucleotide synthesis. We investigated the association between a common polymorphism (C677T, reduced MTHFR activity) and colorectal adenomas within the Minnesota CPRU case-control study. Cases (n 5 527) were diagnosed with colonoscopically confirmed adenomas; controls (n 5 645) were derived from the same gastroenterology practice and were polyp free at colonoscopy. Dietary intakes were obtained from a self-administered food-frequency questionnaire prior to colonoscopy. Age- and sex-adjusted odds ratios (ORs) and 95 % confidence intervals for the MTHFR genotype wer