Mood disturbance, but not overall diet quality, is associated with fecal microbiome diversity in free-living adults.

Objectives: To investigate the gut-brain axis, we explored the relationships among mood disturbance (MD), diet quality (DQ), and fecal microbiota in free-living adults.

Methods: A cross-sectional analysis was conducted with data from 75 healthy adults enrolled in two studies. Anthropometrics, 16s rRNA gene sequencing of fecal microbes, DQ as assessed by Healthy Eating Index-2015 (HEI), and MD determined by Profile of Mood States (POMS) were included. Alpha-diversity and DQ differences were explored between low ( = 37) and high MD ( = 38) groups. Spearman correlations were used to investigate relationships between alpha-diversity, DQ, and POMS subscales. Moderation analysis explored the effect of HEI score on the relationship between MD and alpha-diversity.

Results: Participants were mostly white (67%), 54.5 years old (±11.8), and overweight (28.5 ± 6.5 kg/m). Shannon and Simpson indices indicate higher alpha-diversity in participants with low MD compared to high MD ( = 0.004 and  = 0.008, respectively). Simpson and Shannon indices were correlated with subscale of anger (rho = -0.303,  = 0.011; rho = -0.265,  = 0.027, respectively)and total MD (rho = -0.404,  = 0.001; rho = -0.357,  = 0.002, respectively). Refined grains were associated with fatigue and tension subscales (rho = 0.428, <0.001; rho = 0.302,  = 0.014, respectively). DQ did not significantly moderate the relationship between alpha-diversity and mood disturbance ((7, 53) = 2.00,  = 0.072,  = 0.209). Shannon index was a significant predictor of MD ( = -4.39, (53) = -2.55,  = 0.014), but total HEI score and the interaction (Shannon index*HEI score) were not significant.

Discussion: Greater bacterial diversity was associated with lower MD, and DQ was associated with various mood state subscales in this sample of adults.