Medically reviewed by Onikepe Adegbola, MD, PhD
We all believe that any species makes a voluntary decision about their eating habits. May it be humans, dogs, or birds, we decide our food choices. But do you know that these choices are not completely voluntary? They may be affected by some of our microbes.
Researchers at the University of Pittsburgh have shown for the first time that the microbes in animals’ guts influence what they eat by releasing substances that cause them to crave various types of food. The scientists at the National Academy of Sciences published this information in their study “The gut microbiome influences host diet selection behavior”.
Kohl and his team tested the microbes that influence our choice of diets. They experimented on a set of mice that lacked gut microbiota. A mixture of microorganisms from three species of wild rodents with very different natural diets was given to these mice.
Researchers observed that mice chose different nutrients rich food, which indicated that their microbiome influenced their dietary preferences.
Gut Microbiota and Diet Selection
From individual animals to ecological and evolutionary processes, diet choice can have far-reaching effects. There was no specific research on intestinal microbiota that shows its influence on diet choices.
The hypothesis that the gut microbiome may influence host foraging behavior has been discussed for years but has not yet been specifically tested.
However, the scientists demonstrated that germ-free mice colonized by different microbiomes showed significant differences in their voluntary food selection.
Typically, germ-free mice are free of all microorganisms. They are housed in tightly controlled and monitored isolation chambers to prevent contamination. Hence the results are quite precise.
The study results showed that mice colonized with gut microbiota from three rodent species with different foraging strategies selected diets with different compositions of macronutrients.
Their study showed that herbivore-conventionalized mice preferred a diet high in protein to carbohydrates while omnivore- and carnivore-conventionalized mice preferred a diet low in protein to carbohydrates.
Gut Microbes and Tryptophan Mechanism
They found tryptophan, the essential amino acid, is mainly causing the diet choice. It is no surprise that gut and brain cells always communicate to maintain equilibrium. But sometimes microbes in the gut can produce more molecules like tryptophan that affect this communication and change the choice of diet. Tryptophan can travel up to the brain and convert into serotonin. Serotonin is a happy hormone that indicates “satisfied behavior” in our brain. A slight alteration in the tryptophan mechanism produced by gut microbiota can significantly affect food choices.
The study showed that mice with different microbiomes had different levels of tryptophan in their blood. Moreover, mice with more tryptophan in their blood also had more bacteria than produce it in their gut.
As a result, these findings suggest that gut microbiota may influence host diet selection behavior, perhaps by influencing the availability of essential amino acids. Therefore the study explains why gut microbiota may influence foraging behavior.
An integral part of this process involves the intestinal tract, which releases dietary nutrients like essential amino acids that communicate meal quality to the central nervous system. There are also trillions of microbes that live in the intestinal tract, known as the gut microbiome. They can affect many aspects of a host’s behavior, most likely through the interaction of metabolites with the host’s sensory systems.
Trevelline, B. K., & Kohl, K. D. (2022). The gut microbiome influences host diet selection behavior. Proceedings of the National Academy of Sciences of the United States of America, 119(17), e2117537119. https://doi.org/10.1073/pnas.2117537119