Anxiety associated with dietary intake and gut microbiome features in a cross-sectional cohort of sub-clinically anxious young women.
Emerging evidence highlights the gut-brain axis as a key pathway linking diet and anxiety, but the specific dietary and gut microbiome drivers remain unclear. In this study, we investigated associations between dietary intake, gut microbiome composition, and anxiety in a subclinical cohort of 46 females (18–24 years) from the United Kingdom.  Long-term diet quality was assessed using the Healthy Eating Index (HEI-2020) derived from a food frequency questionnaire, stratifying participants into lower and higher diet quality clusters. Short-term dietary intake was assessed via 24-hour recalls. Shotgun metagenomics of stool samples was used to assees differences in a and ß diversity indices, species abundances, and bacterial pathways putatively metabolizing gut-brain-axis relevant molecules. Anxiety was measured using the State–Trait Anxiety Inventory (state subscale – STAI-s).  Regression models identified diet quality (HEI cluster) as the primary dietary feature of anxiety variation. The presence of Ruminococcus B gnavus and Flavonifractor plautii, and the abundances of several species were positively associated with STAI-s, with Bilophila wadsworthia explaining 40% of its variance. The presence of Feacalibacterium prausnitzii and greater abundances of butyrate, propionate, and GABA synthesis pathways were inversely associated with anxiety. Non-linear models revealed a U-shaped relationship between inositol synthesis and STAI-s. Finally, we found that habitual diet quality may modulate anxiety-related responses to short-term dietary variation.  These findings reveal widespread links between long-term diet quality, microbiota composition and function, and anxiety symptoms. These results point towards several promising targets for prebiotic, probiotic, postbiotic, and dietary interventions targets aimed at reducing anxiety.