Abstract
Previous studies suggest that the gut microbiota may contribute to the onset of depression and that dairy consumption may affect the gut microbiota and alleviate depressive symptoms. This study aimed to investigate the relationship between dairy consumption, gut microbiota composition, and its metabolites in patients with major depressive disorder （MDD）. Fecal samples were collected from 32 participants with MDD and 34 age- and sex-matched healthy controls （HCs）. The gut microbiota composition and its metabolites were analyzed. Dairy intake was evaluated using the Brief-Type Self-Administered Dietary History Questionnaire. Depression severity was assessed using the Hamilton Depression Rating Scale （HDRS）. The effects of depression status （MDD versus HC groups） and dairy intake on the gut microbiota were examined using a two-way analysis of variance. We found interactions between the effects of depression status and dairy intake on the abundance of the family Lactobacillaceae （F ［1,62］＝4.265, uncorrected p＝0.043） and the genera Lactobacillus （F ［1,62］＝4.044, uncorrected p＝0.049） and Megasphaera （F ［1,62］＝
5.739, uncorrected p＝0.020）. Additionally, pelargonate concentrations were correlated with depression severity （HDRS score: rs＝−0.375, uncorrected p＝0.034） and dairy intake （rs＝
0.363, uncorrected p＝0.041）. Dairy consumption may be associated with specific gut microbiota and its metabolites in patients with MDD. Further large-scale studies are required for in-depth characterization of the relationship between dairy intake and gut microbiota and its metabolomes in patients with MDD.
