The role of dietary intake of live microbes in the association between leisure-time physical activity and depressive symptoms: a population-based study

Current research has shown promising associations between factors such as diet, total physical activity, and mental health outcomes, acknowledging the intricate interplay between these variables. However, the role of dietary intake of live microbes, coupled with leisure-time physical activity (LTPA), in their relationship to depressive symptoms necessitates further exploration. The present study examined a cohort of 25 747 individuals who participated in the National Health and Nutrition Examination Survey between the years 2007 and 2018. Patient's Health Questionnaire (PHQ-9) was employed, whereby individuals scoring ≥ 10 were classified as exhibiting symptoms of depression. LTPA status was reported by the Global Physical Activity Questionnaire and calculated by metabolic equivalent-minutes/week. Foods consumed by participants were evaluated by live microbes per gram, which were categorized into three groups: low, medium, and high. After controlling for all covariates, findings indicated that LTPA was negatively associated with depressive symptoms (OR (95% confidence interval (CI): 0.983 (0.976, 0.990), <i>p</i> < 0.001). Participating in more LTPA was positively correlated with consuming all three levels of dietary live microbes (low, β (95% CI): 0.086 (0.063, 0.109); medium, β (95% CI): 0.009 (0.007, 0.012); high, β (95% CI): 0.002 (0.001, 0.002)). Moreover, taking more foods with medium live microbes was associated with lower depressive likelihood (OR (95% CI): 0.931(0.882, 0.982), <i>p</i> = 0.010). Intake of medium and high levels of live microbes mediated the association between LTPA and depressive symptoms by 4.15% and 0.83%, respectively. Dietary intake of foods containing medium and high levels of live microbes may be a mediator of LTPA's negative association with depressive symptoms.