Dietary fibre intake and suicide in Japanese adults: the Japan Public Health Center-based Prospective Study

Abstract Dietary fibre intake has been reported to be inversely associated with depression in a meta-analysis. However, most studies were cross-sectional, and none examined the association with suicide, a severe outcome of depression. We investigated the association of dietary fibre intake with suicide risk among Japanese adults. Participants were 40 630 men and 48 178 women aged 44–76 years who responded to the second survey (baseline of the present study) of the Japan Public Health Center-based Prospective Study (1995–1998). Dietary fibre intake was assessed using a validated FFQ. Hazard ratios of suicide through December 2018 were estimated using Cox proportional hazard regression analysis. During a mean follow-up of 18·7 years, we identified 459 deaths from suicide. Dietary fibre intake was associated with lower suicide risk after adjustment for covariates, including intakes of vitamin B 12 , vitamin D, Ca, Zn and n -3 PUFA. The multivariable-adjusted hazard ratio for suicide of the highest v . lowest quartile of total dietary fibre intake was 0·65 (95 % CI 0·46–0·93). Similar inverse associations were observed for vegetable and fruit fibre intake but not cereal or bean fibre. However, these associations were substantially attenuated and no longer statistically significant after adjustment for nutrients highly correlated with dietary fibre intake, including folate, vitamin B 6 , Mg and Fe; the corresponding value for total dietary fibre intake was 0·85 (95 % CI 0·55–1·31). Our findings suggest that greater consumption of foods rich in dietary fibre and related nutrients, rather than dietary fibre per se, may play a protective role against suicide.