Comparison Between Two Divergent Diets, Mediterranean and Western, on Gut Microbiota and Cognitive Function in Young Sprague Dawley Rats.

Clinical studies strongly suggest the importance of diet quality on cognition in youth populations (15-24 years). The Mediterranean diet (MeDi) has been shown to improve cognition in contrast to the commonly consumed Western diet (WD). The gut microbiota may serve as a mechanism for diet-induced changes in cognition. Ten-week-old male Sprague Dawley rats were assigned a MeDi or WD (n=10/group) for 14 weeks. Prior to neurobehavior assessments, microbiota community composition was assessed. At the genus level, the relative abundance of four bacteria increased with the MeDi and five decreased compared to the WD. Rats in the MeDi group demonstrated cognitive flexibility and improvement in reference and working memory relative to the WD group. At the end of the study, serum cytokines were increased, and low-density lipoproteins were decreased in the MeDi group. Markers for neuroinflammation, blood-brain barrier, glial cells, and synaptic plasticity in brain regions did not differ between groups. Overall, the MeDi modulated gut microbiota, cognitive function, and serum lipid and cytokines but not gene expression in the brain compared to the WD. Further studies are needed to determine causality between diet-modulated gut microbiota, cognitive function, and immune function.