Folate, vitamin B6, vitamin B12 and methionine intakes and risk for nasopharyngeal carcinoma in Chinese adults: a matched case-control study.

Many studies have suggested that folate-related one-carbon metabolism-related nutrients may play a role in certain cancer risks, but few studies have assessed their associations with the risk for nasopharyngeal carcinoma (NPC). In this study, we investigated the association between four folate-related one-carbon metabolism-related nutrients (folate, vitamin B6, vitamin B12 and methionine) and NPC risk in Chinese adults. A total of 600 patients newly diagnosed (within 3 months) with NPC were individually matched with 600 hospital-based controls by age, sex and household type (urban v. rural). Folate, vitamin B6, vitamin B12 and methionine intakes were measured using a validated seventy-eight-item FFQ. A higher dietary folate or vitamin B6 intake was associated with a lower NPC risk after adjusting for potential confounders. The adjusted OR of NPC for quartiles 2-4 (v. 1) were 0·66 (95% CI 0·48, 0·91), 0·52 (95% CI 0·37, 0·74) and 0·34 (95% CI 0·23, 0·50) (P(trend)<0·001) for folate and 0·72 (95% CI 0·52, 1·00), 0·55 (95% CI 0·39, 0·78) and 0·44 (95% CI 0·30, 0·63) (P(trend)<0·001) for vitamin B6. No significant association with NPC risk was observed for dietary vitamin B12 or methionine intake. The risk for NPC with dietary folate intake was more evident in the participants who were not exposed to toxic substances than in those who were exposed (P(interaction)=0·014). This study suggests that dietary folate and vitamin B6 may be protective for NPC in a high-risk population.