The enteric nervous system’s network of nerves, neurons, and neurotransmitters extends along the entire digestive tract – from the esophagus, through the stomach and intestines, and down to the anus. Because the enteric nervous system relies on the same type of neurons and neurotransmitters that are found in the central nervous system, some people call it our “second brain.” It is estimated there are equal numbers of bacteria in our GI tract as cells in the human body. These microorganisms have evolved with humans and animals over the centuries.
Dysbiosis (or alterations in the GI bacterial flora) is strongly associated with several mood disorders and other chronic inflammatory diseases in people. Although serotonin is well known as a brain neurotransmitter (promotes a positive feeling), it is estimated that 90 percent of the body’s serotonin is actually made in the digestive tract. Therefore, it would seem prudent to foster a healthy microbiome as growing evidence reveals the link between intestinal dysbiosis and several chronic diseases including those of the brain. As technology advances it has become easier to sequence the gut microbiome and the differences between healthy individuals and those with chronic diseases are becoming more obvious. Microorganisms in the gut also help regulate the body’s immune response. In an ideal circumstance the host’s immune system has symbiotic relationship with the microbes to form an alliance against outside pathogens. If this relationship is disturbed pathogens are more likely to infect the host through the GI tract. While what measures need to be taken to obtain the healthiest microbiome are still up for much debate the importance of it pertaining to neurologic and chronic illnesses is clearer than ever.
David Brewer, DVM, DACVIM (Neurology)
Hope Veterinary Specialists