The interactive effect of methyl-group diet and polymorphism of methylenetetrahydrofolate reductase on the risk of colorectal cancer.

Higher intakes of vegetables have been reported to be associated with a reduced risk of colorectal cancer. Folate, a water-soluble B vitamin, and one of the major micronutrients in vegetables, may be partly responsible for this beneficial effect. Conversely, a high alcohol intake has been related to an increased risk of colorectal cancer. The combination of high folate and low alcohol intake, "methyl group diets", was reported to have a strong protective effect. These findings support a role of methyl group availability as an underlying mechanism for an effect of folate on colorectal carcinogenesis. The protective effect of the homozygous variant TT form of the MTHFR genotype (C677T) on the risk of colorectal cancer seems to be modified by the level of methyl diets, that is, by folate, which has a protective effect, or conversely by alcohol. Recommendation of higher intake of folate and lower intake of alcohol to the target population, especially those with TT genotype of MTHFR, may be an effective preventive approach against colorectal cancer.