Association of B vitamins and methionine intake with the risk of gastric cancer: The Japan Public Health Center-based Prospective Study.

Dietary intake of B vitamins and methionine might associate with carcinogenesis due to their role in DNA synthesis and methylation. Owing to the previous inconsistent findings on gastric cancer (GC) risk, we aimed to examine the associations between dietary intakes of B vitamins and methionine and the risk of GC, according to sodium intake. We included 86,820 Japanese individuals who completed a validated food frequency questionnaire with 138 food items in the Japan Public Health Center-based Prospective Study. Cox proportional hazard regression was used to obtain hazard ratios (HRs) and 95% confidence intervals (CIs) of GC according to separate intakes of folate, vitamin B6, vitamin B12, and methionine after adjusting for confounding factors, including Helicobacter pylori and atrophic gastritis in the subgroup analysis. We identified 2,269 GC cases within a median of 15.4 years of follow-up. We found no association between any of the dietary intakes of folate, vitamin B6, vitamin B12, or methionine with the risk of GC. In the stratified analysis by sodium intake, we observed a positive association between folate intake and risk of GC among participants with a high sodium intake ({greater than or equal to} 4.5 g/day) (HR=1.28 [95% CI: 1.06-1.56], p trend=0.001; p interaction=0.02). Meanwhile, there was no association between folate intake and risk of GC among participants with low sodium intake (<4.5 g/day) (HR=0.94 [95% CI: 0.73-1.21], p trend=0.49). In conclusion, we found no association between any dietary intakes of folate, vitamin B6, vitamin B12, and methionine with the risk of GC.