If you've been following our reports on how your digestive tract's microbiome benefits your health, you'll be fascinated to know how it can also affect your mood. The human body is a host to an untold number and variety of beneficial bacteria—about 10 pounds of them. Many reside in our intestines and are known as gut microbes. They may be tiny but they are numerous, even outnumbering our cells. Some consider them so important as to be another of the body's organs.
Given their prevalence, scientists have begun cataloging these microorganisms in an effort to better understand how they influence us. Since the beginning of this extensive study, known as the Human Microbiome Project, researchers have been astounded at what they have discovered.
A recent article in The New York Times explains,
Bacteria in the gut produce vitamins and break down our food; their presence or absence has been linked to obesity, inflammatory bowel disease and the toxic side effects of prescription drugs. Biologists now believe that much of what makes us human depends on microbial activity. The two million unique bacterial genes found in each human microbiome can make the 23,000 genes in our cells seem paltry, almost negligible, by comparison.”
A growing number of scientists from around the world are now turning their research to also find ways microbes may communicate with our brains, going so far as to alter our moods and behavior. Why? Micro-organisms in our gut secrete chemicals similar to those used by our neurons to communicate and regulate mood, like dopamine and serotonin. In other words these microbes have the potential to communicate with the nervous system using the same neurochemicals that deliver messages to the brain.
This growing interest in the connection between microbiome and the brain is concentrated on a group of around a thousand species of bacteria which researchers now believe could play a crucial role in psychological ailments such as depression, anxiety, and even autism.
Although these studies have concentrated mostly on mice, humans carry similar strains in their guts. One study included collecting the gut bacteria from an anxious strain of mice and transplanting those microbes into another strain that was more inclined to be calm. The result was that the chilled-out animals seemed to become more anxious.
The link between microbes and autism has focused on the documentation of the digestive and allergic issues in autistic patients. Homing in on this connection, researchers, led by microbiologist Sarkis Mazmanian from California Institute of Technology, concentrated on a common species called Bacteroides fragilis, which is found in some children with autism.
A recent article in The Atlantic explains,
In a paper published two years ago in the journal Cell, Mazmanian and several colleagues fed B. fragilis from humans to mice with symptoms similar to autism. The treatment altered the makeup of the animals’ microbiome, and more importantly, improved their behavior: they became less anxious, communicated more with other mice, and showed less repetitive behavior.”
This type of discovery has led clinics both in Australia and England to offer fecal microbiota treatments for neurological disorders, along with another team in Arizona, which recently finished an open trial on fecal transplants in children with autism.
Even with such promising studies, scientists still caution that while everyone wants to find a cure, it’s important to note that research in this area is far from finished. On the other hand, this connection certainly lends a whole new layer to the saying, "Follow your gut!"
Cartoon by Haidee Merritt
Can the Bacteria In Your Gut Explain Your Mood? Via New York Times
When Gut Bacteria Changes the Brain Function via The Atlantic
The microbiota modulates gut physiology and behavioral abnormalities associated with autism via US National LIbrary of Medicine