Microbiota: Influence on our Brains?

Psychobiotics
Illustration by Andrew Rae

Peter Andrey Smith, reporting for the NYT, asks, "Can the Bacteria in Your Gut Explain Your Mood?" and answers, "The rich array of microbiota in our intestines can tell us more than you might think" (June 23, 2015). Smith introduces us to the work of Dr. Mark Lyte, a pioneer in this field:

Mark Lyte . . . [is interested in the] digestive tube . . . of all vertebrates . . . [for their] vast quantities of what biologists call gut microbiota. The genetic material of these trillions of microbes, as well as others living elsewhere in and on the body, is collectively known as the microbiome. Taken together, these bacteria can weigh as much as six pounds, and they make up a sort of organ whose functions have only begun to reveal themselves to science. Lyte has spent his career trying to prove that gut microbes communicate with the nervous system using some of the same neurochemicals that relay messages in the brain.

This sounds fascinating. And there's more:

Given the extent to which bacteria are now understood to influence human physiology, it is hardly surprising that scientists have turned their attention to how bacteria might affect the brain. Micro-organisms in our gut secrete a profound number of chemicals, and researchers like Lyte have found that among those chemicals are the same substances used by our neurons to communicate and regulate mood, like dopamine, serotonin and gamma-aminobutyric acid (GABA). These, in turn, appear to play a function in intestinal disorders, which coincide with high levels of major depression and anxiety.

So if your gut disagrees with you, it might be right and you wrong:

It has long been known that much of our supply of neurochemicals - an estimated 50 percent of the dopamine, for example, and a vast majority of the serotonin - originate in the intestine, where these chemical signals regulate appetite, feelings of fullness and digestion. But only in recent years has mainstream psychiatric research given serious consideration to the role microbes might play in creating those chemicals.

And thus also turn to interest in the role of these microbes in our mental health and intellectual wealth. Some may say we're chasing a chimera. I say: "Exactly!"