Dietary intake of B vitamins and methionine and prostate cancer incidence and mortality

We investigated prospectively the relationship between dietary intakes of methionine, B vitamins associated with one-carbon metabolism, and risk of incident and fatal prostate cancer. The Melbourne Collaborative Cohort Study recruited 41,514 people aged 40-69 years between 1990 and 1994. During follow-up of 14,620 men for 15 years on average, we ascertained 1,230 incident prostate cancers and 114 prostate cancer deaths. Dietary intakes were estimated using a 121-item food frequency questionnaire. Hazard ratios (HR) and 95 % confidence intervals were estimated using Cox regression. For overall prostate cancer incidence, HRs for riboflavin intake were significantly increased relative to quintile 1 (except quintile 5), with a peak for quintile 3, HR 1.29 (1.07, 1.57). A similar but non-statistically significant pattern existed between riboflavin intake and prostate cancer mortality. The HR for folate intake and overall incidence was significantly increased for quintile 4, HR 1.21 (1.01, 1.46). No association was observed between prostate cancer mortality and the intake of either folate or any other B vitamin or methionine, and no observed association varied by tumor aggressiveness (all P-homogeneity > 0.1). We found little evidence of association between dietary intakes of B vitamins or methionine and prostate cancer risk. Weak associations between prostate cancer incidence and dietary intake of riboflavin and folate, and between riboflavin intake and prostate cancer mortality, need corroboration by other studies.