The gut microbiome influences host diet selection behavior

Yogurt or eggs, steak or veggies, or maybe potato chips? We make decisions about what to eat every day, but those choices may not be fully our own. New research on mice shows for the first time that the microbes in animals' guts influence what they choose to eat, making substances that prompt cravings for different kinds of foods.

Diet selection is a fundamental aspect of animal behavior with numerous ecological and evolutionary implications. While the underlying mechanisms are complex, the availability of essential dietary nutrients can strongly influence diet selection behavior. The gut microbiome has been shown to metabolize many of these same nutrients, leading to the untested hypothesis that intestinal microbiota may influence diet selection. In this research, they have shown that germ-free mice colonized by gut microbiota from three rodent species with distinct foraging strategies differentially selected diets that varied in macronutrient composition. Specifically, they found that herbivore-conventionalized mice voluntarily selected a higher protein: carbohydrate (P:C) ratio diet, while omnivore- and carnivore-conventionalized mice selected a lower P:C ratio diet. In support of the long-standing hypothesis that tryptophan—the essential amino acid precursor of serotonin—serves as a peripheral signal regulating diet selection, bacterial genes involved in tryptophan metabolism and plasma tryptophan availability prior to the selection trial were significantly correlated with subsequent voluntary carbohydrate intake. Finally, herbivore-conventionalized mice exhibited larger intestinal compartments associated with microbial fermentation, broadly reflecting the intestinal morphology of their donor species.

Together, these results demonstrate that the gut microbiome can influence host diet selection behavior, perhaps by mediating the availability of essential amino acids, thereby revealing a mechanism by which the gut microbiota can influence host foraging behavior.

Trevelline, B. K. & Kohl, K. D. The gut microbiome influences host diet selection behavior. Proc. Natl Acad. Sci. USA 119, e2117537119 (2022)