Vitamin B12 Intake and Cancer Risk: Findings from a Case-Control Study in Vietnam.

There is inconclusive evidence on the role of dietary intake of vitamin B in cancer. We evaluated the association between vitamin B intake and cancer risk in a hospital-based case-control study, comprising 3,758 cancer cases and 2,995 controls in Vietnam. Vitamin B intake was derived from the validated food frequency questionnaire. Unconditional logistic regression model was used to calculate the odds ratios (ORs), and respective 95% confidence intervals (CIs) for the association between vitamin B and cancer risk. There was a U-shaped association between vitamin B intake and overall risk of cancer. Individuals with intakes lower than the median intake had a 6% (OR = 1.06, 95% CI: 0.86-1.31)-107% (OR = 2.07, 95% CI: 1.58-2.71), increased risk of cancer (<0.001), whereas those with higher intakes than the median intake had a 20% (OR = 1.20, 95% CI: 0.97-1.48)-52% (OR = 1.52, 95% CI: 1.22-1.89) increased risk of cancer (<0.04). The excess risk of cancer associated with low intakes of vitamin B was observed among esophageal, lung, and breast cancer patients, whereas with high intakes of vitamin B among gastric cancer patients. In summary, a U-shaped association between vitamin B intake and increased cancer risk was observed in the Vietnamese population.