The Microbiome and the Brain: The brain is the newest frontier, yet it has a long history with the stomach. The ancient Greeks, for example, believed that mental problems were caused by an excess of black bile generated by the digestive tract. Long before microorganisms were identified, several philosophers and doctors claimed that the brain and gut worked together to shape human behaviour.
How do bacteria in the stomach affect the brain?
Over the past few decades, scientists have been uncovering this curious relationship and are now using some surprising techniques to fully understand the interplay between the gastrointestinal and nervous systems. Understanding how our microbiomes, and specifically the bacteria we ingest, interact with the human body could help us better treat a range of conditions, including disorders of the brain, the nervous system, and even cancer.
The relationship between mental health and stomach bacteria
In the 1960s, researchers began to observe that gastrointestinal disorders like inflammatory bowel disease and Crohn’s disease coincided with higher rates of schizophrenia, bipolar disorder and depression. This was taken to mean that the gastrointestinal tract and the mind were somehow linked. But the evidence for a link between the two organs was lacking. By the mid-1990s, though, the link between the brain and the gut had come into focus. When researchers observed that patients suffering from schizophrenia, depression, and anxiety consistently possessed a different set of bacteria in their digestive system than healthy control subjects, they dubbed them “proto-psychoses.” But just how did bacteria influence mental health?
How do antibiotics affect the micro-biome?
Antibiotics represent the latest, most dramatic example of this relationship. It turns out that the drugs used to treat bacteria often result in changes in the microbiomes that inhabit human bodies. When you take an antibiotic, a change occurs that changes the community of microorganisms living in your gut. The relationship between the gut microbiome and the central nervous system is not yet fully understood, but we have begun to understand the impact of antibiotics on gut microbes and the host response to the altered gut community. For example, if you take an antibiotic for a short time, your gut microbiome may shift. For a week or two, your gut microbiome will become more diverse.
What do scientists discover about The Microbiome and the Brain?
In recent years, the link between the gut, the brain, and mental health has been making headlines. Scientists are even taking steps to learn more about how the gut—which contains approximately 1,000 different bacterial species—affects the mind. As it turns out, the role of the microbiome in mental health has been a bit of a mystery. Scientists had long suspected that bacteria played a role in the mind, but the evidence wasn’t as clear as we might have hoped. Until recently, most studies suggested that the microbiome played a passive role in mood and cognition. That is, the vast majority of the microbiome’s microbes don’t interact with the host’s nervous system or affect brain function. The link between bacteria and human behaviour was also uncertain.
Conclusion: The Microbiome and the Brain
Once microbes know what to eat, they enjoy a high-powered food source. But this doesn’t mean they won’t look for other resources, and the capacity of the gut to absorb certain nutrients may be limited by the ability of the intestinal environment to support new microbes. Microbes may not be able to fit into an isolated system, and perhaps that’s for the best. So where do you see microorganisms and the human body spending more time in the future? What do they mean for us?