Mental health is not relegated to the brain. In fact, the digestive tract - especially the colon - play a key role in the production and reception of neurotransmitters, which is one of the reasons the gut has been called our 2nd brain. More specifically, the "2nd brain" is the ecosystem of microorganisms (the microbiota) taking up residency in the colon. To learn more about the microbiota read my long-time collaborator, Dr. Barrett's blog titled Microbiome and my previously published blog, This is Your Microbiota on Stress.
One way that the microbiome communicates with the brain is by stimulating the vagus nerve. The vagus nerve travels down the brain stem into the spinal column, innervates the abdomen and then spreads out to create a web-like cage for the digestive tract. Microbes in the colon ”tickle” the vagus nerve to communicate directly with the brain, stimulating production and secretion of neurotransmitters that contribute directly to mental wellness, including serotonin, dopamine and others. Additionally, the microbiota play a significant role in what kind of signaling molecules are produced in the gut that then communicate with the brain.
The microbiota also impacts a part of the brain called the amygdala. The amygdala "...is commonly thought to form the core of a neural system for processing fearful and threatening stimuli, including detection of threat and activation of appropriate fear-related behaviors in response to threatening or dangerous stimuli." The composition of the microbiota - both the overall population and the diversity of the ecosystem - impacts how the amygdala develops a response to stressful stimuli and the extent to which anxiety manifests in an individual. In this way, microbiota modification via diet, lifestyle and therapeutic probiotic supplements holds promise for mental health.
Another way in which the health of the microbiota contributes to the health of the mind/heart is via maintenance of the structural integrity of the digestive tract.
In addition to beneficial microbes like species of lactobacillus and bifidobacteria, we also host strains of streptococcus and staphylococcus, candida and other yeasts. These potentially pathogenic microbes make toxic compounds called lipopolysaccharides (aka endotoxins). Lipopolysaccharides (LPS) dismantle the harmony not just in the colon but in the small intestine too. When the microbiota is imbalanced and the potentially pathogenic microbes gain a stronghold, over time the accumulation of LPS in the digestive tract can cause intestinal permeability or "leaky gut syndrome." In a leaky gut, the barrier of the small intestine is inflamed and compromised to the extent that nutrients are not absorbed and larger molecules escape the digestive tract intact, causing inflammation throughout the body.
With leaky gut we are posed with two factors contributing to mental wellness:
Here are a couple action steps you can take now for your gut - and mental - health:
These recommendations are not going to be appropriate for everyone, so it's always a good idea to consult a health care provider to get an individualized wellness plan.
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