From a superficial standpoint, it may seem like the gut is only responsible for eating, digesting, and absorbing nutrients – but as any functional medicine expert will tell you, this complex organ plays a much bigger role in the body. The microbes living in the gut have a direct line of communication with the brain (called the gut-brain axis) and produce neurotransmitters that affect sleep, mood, and more.
One of these neurotransmitters, called GABA (or gamma-aminobutyric acid), is secreted by two types of bacteria in the microbiome: Lactobacillus and Bifidobacterium, according to a study that examined the role of the gut microbiome in sleep health, our circadian rhythms, and mood.
"GABA enables the mind and body to relax, fall asleep, and sleep soundly all night long," said clinical psychologist and board-certified sleep specialist Michael J. Breus, Ph.D., previously told mbg from GABA Associated with suboptimal sleep and mood.
Another neurotransmitter that is eliminated from the intestines and that plays a role in sleep is melatonin. In fact, "the gut contains at least 400 times more melatonin than the pineal gland," according to a study published in the World Journal of Gastroenterology. Melatonin tells your brain it's time to go to sleep – an essential step in the bedtime process.