Folate, methionine, alcohol, and colorectal cancer in a prospective study of women in the United States.

Objective: We investigated the associations of folate, methionine, and alcohol intake, as well as combinations of these factors, with risk of colorectal cancer (CRC).
Methods: We assessed diet using a 62-item food-frequency questionnaire among 45,264 women in the Breast Cancer Detection Demonstration Project (BCDDP) Follow-up Study. After an average of 8.5 years of follow-up, 490 cases of CRC were identified.
Results: Dietary folate showed only a slight inverse association with the risk of CRC (RR = 0.86, 95% CI 0.65-1.13 for high vs. low quintile, p for trend = 0.14), and the association for total folate was null. Consuming more than two servings of alcohol per day was only slightly associated with CRC in this cohort (RR = 1.16, 95% CI 0.63-2.14). Combinations of high alcohol and low total folate did not result in a higher risk of CRC. There was no association between methionine and colorectal cancer.
Conclusions: This study shows limited association between alcohol intake and CRC. The non-association of total folate and methionine with CRC, and the null results from the combined folate and alcohol analyses, suggest that what effect alcohol may have on CRC is unrelated to the methyl-group metabolism pathway.