Folate intake and risk of colorectal cancer and adenoma: modification by time

Abstract

Background: Experimental and observational studies have suggested that folate may play dual roles in colorectal cancer risk depending on the timing and dose. Objective: We examined the latency between folate intake and the incidence of colorectal cancer. Design: We prospectively examined associations between folate intake assessed every 2 to 4 y by using validated food-frequency questionnaires and risk of colorectal cancer and adenoma in the Nurses’ Health Study and Health Professionals Follow-Up Study, which included 2299 incident colorectal cancers and 5655 colorectal adenomas from 1980 to 2004. Results: There was an association between total folate intake 12–16 y before diagnosis and lower risk of colorectal cancer (relative risk: 0.69; 95% CI: 0.51, 0.94; ≥800 compared with Conclusion: Folate intake is inversely associated with risk of colorectal cancer only during early preadenoma stages.