|This boy may be influencing who he will marry when |
he grows up. Photo by Orrling at Wikimedia Commons.
Much of the early research on the microbiota-gut-brain axis was done using specialized mice that have never been exposed to any bacteria. You may think this sounds like a healthy lifestyle, but these so-called germ-free mice have all kinds of health and behavioral problems. They often have digestive difficulties and high levels of anxiety, symptoms common of people with irritable bowel syndrome (IBS). They also typically have deficits in social behavior and increased repetitive behaviors. Similar to autism-spectrum disorders and obsessive compulsive disorder (OCD), these behavioral problems are more likely to occur in males than in females. When faced with a challenge, many struggle with solving the problem and show a higher tendency to give up, symptoms common in patients with depression. Interestingly, simply feeding germ-free mice some species of Bifidobacteria and Lactobacilli bacteria (similar to bacterial strains found in different brands of yogurt) can reduce symptoms of anxiety, depression, cognitive difficulties, autism, and OCD. This has led to a boom in biomedical research on the benefits of probiotics (that contain microbes that live in our guts) and prebiotics (that contain things that the microbes in our guts eat).
|Yogurt bacteria. Photo by Josef Reischig at Wikimedia Commons.|
How do microbes in our guts affect our brains anyway? Although the answer to this is still mostly unknown, we know that the gut has the potential to influence the brain through multiple means, including hormone production, immune function, and even directly through specific nerves. The specific mechanisms are still being very actively researched, but it is clear that microscopic critters living in our guts likely influence our brains and behaviors in many different physiological ways.
Microbiota-gut-brain axis research is revolutionizing the way we think about health, medical treatments, behavior and even existential questions like who am I? But one thing is for sure: I’m gonna go have another yogurt.
Want to know more? Check these out:
Cryan, J., & Dinan, T. (2015). More than a Gut Feeling: the Microbiota Regulates Neurodevelopment and Behavior Neuropsychopharmacology, 40 (1), 241-242 DOI: 10.1038/npp.2014.224
Ezenwa, V., Gerardo, N., Inouye, D., Medina, M., & Xavier, J. (2012). Animal Behavior and the Microbiome Science, 338 (6104), 198-199 DOI: 10.1126/science.1227412