Exploring the crosstalk between gut microbiota and stool metabolome in omnivorous, vegetarian, and vegan diets: A...

Gut microbiota (GM) and fecal metabolome are shaped by different dietary regimens. Nevertheless, outlining generalized patterns is challenging, due to the intrinsic heterogeneity of individual dietary choices. In this work, the fecal metabolome of adult volunteers consuming omnivorous (n=44), vegetarian (n=29), and vegan diets (n=25) for at least 12 months was characterized. The crosstalk among diet, GM and fecal metabolome was also investigated correlating metabolomics and metataxonomics data. Untargeted metabolomic profiles were correlated with metataxonomics data previously acquired on the same stool samples. The sphingomyelin SM(d18:2/18:1-2OH) and phosphoethanolamines from animal-based food were associated to the omnivorous diet and were negatively correlated to beneficial Bacteroides ovatus and Odoribacter genus. Plant glycerides, sterols, triterpenes, and oleic-linoleic acid were associated with the vegan diet. Oleic-linoleic acid was positively correlated with Alistipes putredinis. Chenodeoxycholic acid, a primary bile acid, was identified as a marker of vegan diet, while ketolithocholic acid, a secondary bile acid, was associated to the omnivorous diet. This latter was also negatively correlated to B.ovatus. Overall, results confirm that assessing markers of dietary regimens instead of specific food categories is challenging, especially if volunteers' diet is not strictly monitored. However, the integration of metabolomics and metataxonomic data allows to better understand the effects of specific food components on the GM and represents a suitable approach for further molecular investigation in nutrition.