The Brain Below Your Belt
Did you know that phrases like “gut-wrenching emotions” and “I felt that in the pit of my stomach” are not just figures of speech? These come from very real neural signals that originate in the gut. You won’t get these neurons to compose orchestras or parse complex thoughts into words, but your belly contains a neural messaging system boasting greater processing capacity than either the peripheral nervous system or spinal cord.
For years, some scientists have been calling this enteric nervous system “the second brain” but recent studies suggest that, from a flow of information perspective, the enteric system may be even higher on the neural totem pole than the more famous, skull-based nerve center. This understanding explains why the food we eat is directly related to our mental state, our overall vitality, and our susceptibility to disease.
Our digestive tract is the 30-foot-long tube through which we absorb nutrition from our food. The walls of this tube are embedded with a dense web of neurons that pass information through the vagal nerve (also known as the ‘wandering nerve’), which connects numerous organs to the brain. We like to think of our brain directing our organs, but 90% of the messages that travel along the vagal nerve move from the gut to the brain rather than the other way around. This begs the shocking question: is our gut telling our brain what to do?
This brain under our belt is also a heavyweight champion of the immune system with as much as 80% of the body’s immune function located in the gut. The vagal nerve can modulate this immune system, which explains many of the mysteries of food sensitivities and also promises future breakthroughs in autoimmune disease treatment.
This is why immune dysfunction affects us not only physiologically, but neurologically as well. This connection is supported by data showing the same nutrition and lifestyle risk factors for heart disease are also risk factors for dementia. And aside from full-blown disease, the enteric nervous system plays a big role in food sensitivities and mood.
Serotonin is a neurotransmitter and hormone related to mood and more than 90% of the body’s serotonin is produced in the digestive tract. It doesn’t stop there. We’ve long suspected that the flora in the gut directly affects hormones, but a recent study by Caltech confirms the theory; mice without gut bacteria produce 60% less serotonin, and even more interestingly, adding bacteria back into these animals’ digestive tracts largely restores the serotonin production. There seems little doubt that food and mood are closely intertwined.
The brain under your belt also explains why gluten is so detrimental to so many people. The red-hot gluten-free diet trend isn’t just a fad – it’s a reaction to a very real nutrient sensitivity. Gluten guru Tom O’Bryan told me recently that he believes gluten, in people sensitive to it, behaves as a neurotoxin. This would explain symptoms of gluten intolerance that include dizziness and numbness in the hands and feet as well as neuropathy that occurs in people with gluten sensitivity who do not limit their gluten intake. Studies support O’Bryan’s theory: removing gluten from the diet reduces the symptoms of neuropathy while continued gluten consumption causes further deterioration.
The brain in the head is protected, to some degree, from environmental insults by the blood-brain barrier, provided the network of capillaries that makes up the blood-brain barrier is in good condition. The brain under the belt also has a protective barrier, the endothelium of the intestines. When working properly, this endothelium lets in the good stuff and keeps out the bad. When the endothelium is compromised, as in the case of inflammatory bowel diseases like ulcerative colitis or nutrient sensitivities, the endothelium initiates an inflammatory, protective response that causes more harm than good. Among other things, this causes the intestines to become more permeable, allowing bacteria, partially digested food, and other unwanted elements to pass the endothelium and trigger an additional inflammatory immune response as the body attempts to rid itself of the invaders. The inflammation alters the physiology of the neurons of the enteric nervous system, spreading the message of inflammation far from its point of origin.
This all adds up to an increased understanding of the damage done to other parts of the body when the brain under our belt is compromised. Long known as ‘leaky gut,’ this concept of intestinal permeability shows us how damage from antibiotics, food intolerances, and infections can cause the enteric nervous system to become inflamed and ‘confused’. This confusion leads to chronic damage to other parts of the body through ‘molecular mimicry’ where innocuous food particles can become nuclear warheads to parts of the body far away.
So next time somebody suggests a junk food meal, you can reply, “The brain under my belt really doesn’t like that idea.”