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Dr. Kharrazian: To look at some of the research that’s been done, with traumatic brain injuries and how it impacts the gut. The advantage of looking at some of these studies with traumatic brain injuries and how it impacts the gut is because you have a rapid loss of function with a traumatic brain injury. If someone has a neurodegenerative process, the brain starts to slowly degenerate, degenerate and degenerate.

Then you start to lose vagal function subtly so it becomes hard to understand how the brain is really, in fact, impacting the gut. But when you look at research done on brain injuries, you have brain function and gut function that are at a baseline and then all of a sudden the brain gets injured and then they can measure changes in the gut and they can really understand these relationships that are taking place between the brain and the vagal pathways. 

There’s a paper that I published called Traumatic Brain Injury That Affects The Gut that’s available at the national library of medicine, if you’re interested in that paper, and you go through all the different pathways that are involved with that, but just to make things very simple, the illustration is you have trauma to the brain.

Now, this could be neurodegeneration, this could be, neurodevelopment. The same pathways would eventually take place and there’s impaired vagal motor activity. That’s the area of the brainstem that controls bowel movement, and then that reduces the contractibility of the intestines and then you lose the ability to have proper motility. When you lose the ability to have proper motility, you impact also what’s called bacterial translocation, how bacteria move across the gut, and that is critical for healthy microbiome function.

The vagal aspects of the brain, the vagal motor activity to the brain, also control a major valve called the ileocecal valve between the small and large intestine. What that valve does is that it keeps bacteria that should only be in the large intestine, in the large intestine, and when that bacteria gets translocated or moved into the small intestine because the brain can’t control that very well, you get things like small intestinal bacterial overgrowth and you get major changes in the gut microbiome.

People that end up with traumatic brain injuries also have lots of what’s called dysautonomia. They have altered blood flow and function to the gut, their heart rate goes all over the place. Those are really typical to see, and there’s also some pretty good research that as soon as you lose that Vagal tone from the brain to the gut, that there’s a development of intestinal permeability. AThe intestinal mucosa becomes compromised and the immune cells in the gut basically get activated, and the entire gut microbiome changes into an inflammatory state and different bacterial species become more populated or less populated based on all these various factors.