Association of the newly proposed dietary index for gut microbiota and depression: the mediation effect of phenotypic age and body mass index.

BACKGROUND: Gut microbiota and depression have garnered attention. The dietary index for gut microbiota (DI-GM) is a newly proposed index that reflects the diversity of gut microbiota, yet its association with depression remains unstudied. METHODS: Data from the National Health and Nutrition Examination Survey were analyzed. Depression was assessed using Patient Health Questionnaire (PHQ-9). Dietary recall data were used to calculate the DI-GM (including components beneficial and unfavorable to gut microbiota). Multivariable weighted logistic and linear regression were employed to investigate the association of DI-GM with depression and total PHQ-9 score. The potential mediating role of phenotypic age and body mass index (BMI) was explored. Secondary analyses included subgroup analyses, restricted cubic spline (RCS), and multiple imputation. RESULTS: A higher DI-GM and beneficial gut microbiota score were associated with a lower prevalence of depression (DI-GM: OR = 0.94, 95% CI = 0.89, 0.99; beneficial gut microbiota score: OR = 0.88, 95% CI = 0.82, 0.94) and lower total PHQ-9 score (DI-GM: ß=-0.09, 95% CI=-0.14, -0.04; beneficial gut microbiota: ß=-0.15, 95% CI=-0.21, -0.08). RCS indicated a non-linear relationship between DI-GM and depression. A significant mediating effect of phenotypic age (proportion of mediation: 19.81%, 95% CI: 12.86-63.00%) and BMI (proportion of mediation: 16.49%, 95% CI: 12.87-62.00%) was observed. CONCLUSIONS: The newly proposed DI-GM was negatively associated with the prevalence of depression and total PHQ-9 score. Mediation analyses demonstrated a significant mediating effect of phenotypic age and BMI.

The Development and Evaluation of a Literature-Based Dietary Index for Gut Microbiota.

The aim of the study was to develop and evaluate a novel dietary index for gut microbiota (DI-GM) that captures dietary composition related to gut microbiota profiles. We conducted a literature review of longitudinal studies on the association of diet with gut microbiota in adult populations and extracted those dietary components with evidence of beneficial or unfavorable effects. Dietary recall data from the National Health and Nutrition Examination Survey (NHANES, 2005-2010, n = 3812) were used to compute the DI-GM, and associations with biomarkers of gut microbiota diversity (urinary enterodiol and enterolactone) were examined using linear regression. From a review of 106 articles, 14 foods or nutrients were identified as components of the DI-GM, including fermented dairy, chickpeas, soybean, whole grains, fiber, cranberries, avocados, broccoli, coffee, and green tea as beneficial components, and red meat, processed meat, refined grains, and high-fat diet (≥40% of energy from fat) as unfavorable components. Each component was scored 0 or 1 based on sex-specific median intakes, and scores were summed to develop the overall DI-GM score. In the NHANES, DI-GM scores ranged from 0-13 with a mean of 4.8 (SE = 0.04). Positive associations between DI-GM and urinary enterodiol and enterolactone were observed. The association of the novel DI-GM with markers of gut microbiota diversity demonstrates the potential utility of this index for gut health-related studies.