Transitioning to a more plant-based diet with increased fiber can cause significant shifts in the gut microbiome with variable effects on how individuals feel.

“Likewise, some people go from ingesting animal products including meat or they're vegetarian and they go to vegan and they experience positive shifts in mood and affect. And we know that the transition to a more plant-based diet and especially the enrichment of fiber that's present in those diets also creates dramatic shifts in the gut microbiome. Some people feel better doing that. Some people feel worse.”