Association of dietary intake of live microbes with bowel health and depression in US adults: a cross-sectional study of NHANES 2005-2010.

Background: Depression substantially impacts on quality of life, personal relationships, and self-care. Gastrointestinal disorders are the common comorbidity of depression and 24.3% of patients with depression have disordered bowel habits. Dietary intake of live microbes alters the host's microflora and is beneficial for the prevention and control of bowel health and depression. We aim to investigate the association of dietary intake of live microbes with bowel health and depression and to further examine weather bowel health or depression mediates the therapeutic effect of live microbes.

Methods: Participants' data were obtained from the National Health and Nutrition Examination Survey (NHANES) 2005-2010, which is designed to examine the health and nutritional status of the non-institutionalized US population by a complex, multi-stage, probability sampling design. The foods were grouped into categories on the basis of estimated microbial levels: low (<10⁴ CFUs/g), medium (Med; 10⁴-10⁷ CFU/g), and high (Hi; >10⁷ CFU/g). Participants were further classified into three groups (G1: participants without MedHi foods intakes; G2: those with MedHi foods intakes greater than zero but less than the median; and G3: those with MedHi foods intakes greater than the median).

Results: A total of 10,785 US adults were selected. The median of MedHi foods intake was 66.1 g/day. Participants in the G2 (OR = 0.739, 95% CI: 0.581-0.941) and G3 (OR = 0.716, 95% CI: 0.585-0.877) groups had significant association with lower risks of depression, and participants in the G3 group had significant association with lower risks of hard stools (OR = 0.885, 95% CI: 0.692-0.989) and loose stools (OR = 0.769, 95% CI: 0.585-0.954). Interestingly, further mediation analyses showed that the association of dietary live microbe intake with depression is mediated by the stool types, and the association of dietary live microbe intake with stool types is mediated by the depression (all P < 0.05).

Conclusions: A high dietary intake of live microbes, especially a minimum of 66.1 g of MedHi foods per day, is associated with a lower risk of depression, hard stools, and loose stools consistency. Depression and bowel health mutually act as mediators in this association, indicating dietary intake of live microbes may simultaneously affect bowel health and depression.