On this episode of Science to Save the World, Lifespan.io’s general science show, we discuss what we can learn and how we can benefit from understanding our microbiomes as part of ourselves.
During this time period, the three most important factors that influence the development of our unique microbiomes are: genetics, the process of birth, and breast feeding. Research has shown that babies that are born via C-section have vastly different microbiomes than those that are born by vaginal delivery.
Further, babies born by C-section tend to develop microbiomes associated with compromised immune systems and predispositions to metabolic diseases such as type 2 diabetes and obesity. But this does not mean that our microbiomes and corresponding health prospects are “set in stone” at these early time points.
Although the sequence of exposure to microbes seems to play a major role in how they inhabit the ecosystem of the body, our microbiome still retains the potential for dynamic change as we age. The composition of our microbiome has been shown to change in response to diet, lifestyle factors, and drugs. Just how interconnected are we with our microbial inhabitants, and how can understanding this relationship lead to a better understanding of ourselves?
The gut microbiome is by far the largest and most dense community of microbes that colonizes our bodies. It serves many roles, including aiding in the digestion of food, maintaining the integrity of our intestine, and the production of metabolites and hormones required for healthy physiological functioning. In fact, research has shown that ten percent of the metabolites found in our blood circulation that are required for health and wellness are produced within our gut microbiome.
In essence, each bacterium in our gut microbiome is a tiny “drug factory”, producing vitamins, hormones, lipids, and neurochemicals that influence our brain, immune system, and systemic metabolism. The science of how the gut microbiome influences our brain health and behaviors is one of the hottest fields of research today.
Gut bacteria produce hundreds of metabolites that the brain uses to regulate basic physiological processes as well as mental processes such as learning, memory and mood. This includes critical neurochemicals such as norepinephrine, dopamine, acetylcholine, melatonin, and seratonin. In fact, our gut microbiome manufactures about 95% of the body’s supply of serotonin, which influences both mood and GI activity.
Another way the microbes on our skin and in our GI tract influence the brain is by co-opting the immune system itself, using immune cells and the chemicals they synthesize to send messages to the brain. The GI tract contains the highest concentration of immune cells in the body and they are constantly sensing and responding to the microbes in our gut and the molecules they produce.
Studies suggest that defensive molecules called inflammatory cytokines, produced by these immune cells, disrupt brain neurochemistry and make people more vulnerable to anxiety and depression. Researchers believe that this process may help explain why more than half of people with chronic GI disorders such as Crohn’s disease, ulcerative colitis and irritable bowel syndrome (IBS) are also plagued by anxiety and depression.
A third mechanism by which our gut microbiome communicates with our brain is through the largest nerve in the body, the vagus nerve. The vagus nerve serves as the body’s superhighway, carrying information between the brain and the internal organs and controlling the body’s response in times of rest and relaxation. Research has shown that the vagus nerve is a means of bidirectional communication between our brain and our gut microbiome. Therefore, our emotional dispositions influence inflammation in the gut, which in turn influences our gut microbiome.
And anti-inflammatory molecules produced by our gut microbiome can improve mood by altering brain biochemistry. Our novel understanding of the intricate interactions between a host and its microbes has led to the concept of the “holobiont”, meaning the biological entity of a host and its associated microorganisms.