Graphics courtesy of Open Clip Art
BY SABRINA EDWARDS '20
Kombucha and yogurt fans rejoice: New research implies a connection between mental health and the health of the bacteria in our stomachs and intestines — otherwise known as the “gut.” Health food gurus have long hailed the benefits of fermented foods and probiotics for the health of the community of bacteria in our gut, or our internal “microbiome.” According to the Human Microbiome Gut Initiative, based out of the Human Genome Project at Washington University, the microbiome in our gut is significantly larger than any other microbiome in our bodies. This highly concentrated group of various species of microbes has been attributed a number of digestive functions critical to humans such as the ability to break down certain kinds of fats.
A study written by M. Carabotti and A. Scirocco in 2015 states that certain bacteria found in the gut appear to be “regulating brain chemistry and influencing neuro-endocrine systems associated with stress response, anxiety and memory function” in their subjects. This finding, based on the presence of certain neurotransmitters and their interactions across the “gut-brain axis,” has serious implications for future research of mental health, since the concept of brains and stomachs communicating seems so counterintuitive.
Mount Holyoke biology professor Jason Andras recognizes this dissociation of gut from brain and attributes it to a mentality that “all our cognitive function happens in our brains and most of the bacteria on our bodies live in our guts. Those are physically separated and there was no known mechanism that the bacteria in the gut could affect cognitive function in the brain.”
However, appearances may be deceiving in how we consider our bodies to be connected. Professor Andras explained, “There’s a major nerve called the Vagus nerve which is the nerve that runs from our gut up to our brain but previously it wasn’t really believed that the Vagus nerve was serving as a means of communication between the gut bacteria and our brain. But now we believe that it might be.”
The Vagus nerve, the longest of the cranial nerves, has been the subject of various studies of communication between our guts and our brains, and it provides the plausible link between our brains and the large amounts of neurotransmitters produced by our intestinal microbiome.
Neurotransmitters are plentiful in our gut. “Some of the highest concentrations of serotonin in our bodies are in our gut actually and serotonin is the same important neurotransmitter that is the target of a lot of, or the receptors for serotonin, are the target of a lot of antidepressant drugs” Andras explained. The large quantities of these key neurotransmitters are what leads scientists to believe that the Vagus nerve is sending information from the gut to the brain. Further studies with mice identified that the presence or lack of the bacteria producing these neurotransmitters had a significant impact on the mice’s moods and anxiety.
As we continue to explore the interactions between both the human-bacterial genomes as well as the neurotransmitters relayed along the gut-brain axis, the therapeutic implications could completely alter how we approach certain mental health issues. However, the exact mechanisms connecting the brain and gut remain unclear, preventing certain strides in therapeutic applications. Carabotti and Scirocco in their 2015 study suggest “a potential role of certain probiotic strains as novel adjuvant strategy for neurologic disorders,” meaning that for mental health issues connected to bacteria found in the gut, probiotics and other kinds of bacterial therapy might provide a new method for treating mental illness.