Folate Intake, Alcohol Consumption, Cigarette Smoking, and Risk of Colorectal Adenomas

Abstract

Background: Recent evidence suggests that folic acid (and derivatives) could contribute to the protective effect of fruits and vegetables against the risk of large-bowel cancer. Other evidence in dicates that alcohol drinking and ciga rette smoking may impair the biologic actions of folate. We used data from an adenoma prevention trial to investigate the occurrence of colorectal adenomas (possible precursors of colorectal can) in association with folate intake, alcohol consumption, and cigarette smoking. Methods: Patients with at least one recent large-bowel adenoma were followed with colonoscopy 1 year and 4 years after their qualifying colon examinations. Adenomas detected after the year 1 examination were used as end points. A food-frequency question naire was administered at study entry and at study completion; nutrient in take at study entry was used in this analysis. All statistical tests were two. Results: After adjustment for ca loric intake, dietary folate had a signifiprotective association with the risk of recurrence of large-bowel adenoma (P for trend = .04). However, this in verse association was attenuated by further adjustment for intake of di etary fiber and fat. Use of folate supple ments was not associated with a reduc tion in risk. Alcohol intake (seven or more drinks) was associated with increased risk (odds ratio = 2.04; 95% confidence interval = 1.28–3.26). Cigasmoking, even smoking for long duration, was not related to adenoma recurrence. Conclusions: These data provide only modest support for previ ous findings suggesting beneficial ef fects of folate on colorectal adenoma risk. We find no evidence that cigarette smoking increases risk. These findings do suggest a substantial increase in risk with alcohol consumption. [J Natl Can cer Inst 1998;90:57-62]