Dietary fiber intake, depression, and anxiety: a systematic review and meta-analysis of epidemiologic studies

Background:: Findings of previous studies on relationship between dietary fiber intake and depression were inconsistent. We performed a meta-analysis on the association of dietary fiber intake with depression and anxiety in epidemiologic studies. Methods:: We conducted a systematic search of electronic databases, up to May 2021. Data from 18 publications (12 cross-sectional, five cohort and one case-control studies) on dietary fiber consumption in relation to depression or anxiety were included. For depression, fifteen studies were conducted on adults and three others on adolescents. Anxiety was not included in the analysis, due to insufficient eligible studies. Results:: Total dietary fiber intake was associated with a 10% lower odds of depression (OR = 0.90; 95% confidence interval [CI]: 0.86, 0.95) in adults and a 57% lower odds (OR = 0.43, 95% CI: 0.32, 0.59) in adolescents. Dose-response meta-analysis revealed an inverse linear association between total dietary fiber intake and odd of depression in adults; such that each 5-g increase in total dietary fiber intake was associated with a 5% reduction in risk of depression (OR = 0.95; 95% CI: 0.94, 0.97). An inverse significant association was observed between intake of fiber from vegetables (OR = 0.73; 95% CI: 0.66, 0.82) and soluble fiber (OR = 0.80, 95% CI: 0.71, 0.91) and odds of depression. However, cereal fiber, fiber from fruits and insoluble fiber were marginally associated with a reduction in having depression. Conclusions:: High intake of dietary fiber was protectively associated with depression in adults, in a dose-response fashion.