Dietary intake of folate and alcohol, MTHFR C677T polymorphism, and colorectal cancer risk in Korea.

BACKGROUND The incidence of colorectal cancer (CRC) is increasing sharply in Korea, and evidence has suggested the role of dietary methyl supply and related polymorphisms on colorectal carcinogenesis. OBJECTIVE We investigated the association between folate and alcohol intake, methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism, and CRC risk in Koreans. DESIGN A total of 787 cases and 656 controls were recruited from 2 university hospitals. Multiple logistic regression models were used to estimate ORs and corresponding 95% CIs. RESULTS MTHFR 677T homozygotes were at a lower risk of CRC (OR: 0.60; 95% CI: 0.46, 0.78 for TT compared with CC/CT). High folate intake was associated with reduced CRC risk (OR: 0.64; 95% CI: 0.49, 0.84 for high compared with low intake), and high alcohol consumption was associated with increased risk of CRC (OR: 1.76; 95% CI: 1.26, 2.46 for high compared with low intake). When data were stratified by the amount of dietary methyl (combined intake of folate and alcohol), those with low-methyl diets had higher risk of CRC (OR: 2.32; 95% CI: 1.18, 4.56) than did those with high-methyl diets among CC/CT carriers, whereas the amount of dietary methyl did not affect the CRC risk among carriers with the TT homozygous variant. This association was stronger in patients with colon cancer than in patients with rectal cancer. CONCLUSION We found that the effect of dietary methyl supply on colorectal carcinogenesis may differ according to MTHFR C677T genotype and the subsite of origin in a Korean population.