ISTOCK, PERCEPTION7The community of microorganisms living in the human gut, estimated to total 100 trillion, may have a profound effect on many aspects of our physiology, including immunity, metabolism, and even our brain and behavior. The majority of studies on the latter have so far been conducted in animals, demonstrating that gut bacteria (especially species belonging to Lactobacillus and Bifidobacterium) can influence social behavior, anxiety, stress, and symptoms of depression. For instance, supplementation with a Lactobacillus species has been found to increase sociability in stressed mice, while germ-free mice exhibit impaired social behavior.
There are several possible mechanisms by which gut bacteria may affect the brain, including communication via the vagus nerve (the major neural link between the gut and brain), the immune system, and hormonal changes. It is also particularly intriguing that some gut bacterial species can produce chemicals of identical structure to our brain’s own neurotransmitters. This emerging evidence of the intricate links between the gut microbiome and the brain begs the question of whether bacteria have evolved to alter our neurochemistry and behavior in ways that benefit themselves.
It is an appealing proposition that gut microbes may manipulate our behavior for their own advantage, such as improving their transmission to new hosts or enabling them to acquire food. For example, several prominent researchers in the ...
