How Leaky Gut Connects to Leaky Brain

Written by Carley Squires, ND, LAc

There is a two-way communication between the brain and the gastrointestinal tract often referred to as the “brain–gut axis,” so it makes sense that increased inflammation in one would result in inflammation of the other. But, how do we get inflammation in the gut or brain? And, how exactly do they communicate?

Let’s first talk about intestinal permeability. It is not a matter of if you have intestinal permeability it is more a matter of how much intestinal permeability you have. Intestinal permeability comes from increased inflammation in your digestive tract. Many people have inflammatory reactions in their digestive tract from eating inflammatory foods. The standard American diet alone is going to cause inflammation in the digestive tract due to preservatives, pesticides, binders, antibiotics, antimicrobials and increased sugars. Processed foods are filled with inflammatory proteins like corn, dairy, soy, and sugars. Other factors such as exposure to environmental toxins, gastrointestinal infections, prolonged use of antacids, antibiotics or steroids, stress responses and hormonal imbalances all lead to intestinal permeability and increased inflammation.

Increased intestinal inflammation creates a breakdown of the digestive tract lining that normally is providing a protective barrier. Permeability leads to exposure of toxins, microbes, and food proteins into the bloodstream signaling the immune system that it has been invaded, which signals an inflammatory reaction to deal with the foreign invasion. Prolonged exposure results in chronic inflammation, immune system dysfunction, food intolerances, allergies, discomfort while eating and eventually chronic inflammation in all body tissues.
How does intestinal inflammation affect the brain?

The digestive tract communicates with the brain by way of the vagus nerve. The vagus nerve is one of the main nerves controlling the part of the nervous system considered the “rest and digest” which controls mood, immune response, digestion, and heart rate. When there are inflammatory signals in the digestive tract those signals are being carried to the brain and trigger inflammatory signals in the brain and vice versa. What current research is showing is that inflammatory conditions, whether it’s celiac disease, ulcerative colitis, or inflammatory bowel disease are all having an inflammatory impact in the brain.

The brain can also be affected by inflammatory signals both locally and systemically turning on glial cells. Glial cells provide our nervous system with structural, functional and immunological support. Traumatic brain injury turns on glial cells, diabetes turns on glial cells, inflammatory bowel disease turns on glial cells, autoimmune diseases turn on glial cells and so on. Whenever there are inflammatory signals happening in the body or brain those signals can open up the doors and increase the permeability of the blood-brain barrier, which activates inflammatory cascades. Chronic inflammation and permeability of the blood-brain barrier can result in neurodegenerative diseases such as Alzheimer’s and Parkinson’s.

How can inflammation in the brain affect the digestive tract?

As we have said there is a brain-gut axis, and there is a gut-brain axis. If you get neurodegeneration, you’re going to have an effect on the digestive tract. If you have digestive tract inflammation, you’re going to have an effect on the brain. Individuals that experience a traumatic brain injury within thirty-six to seventy-two hours have signs of intestinal inflammation and digestive tract permeability. The inflammation within the brain from a traumatic brain injury causes damage to neurons resulting in loss of signaling from the vagus nerve to the digestive tract leading to intestinal permeability, which initiates an inflammatory cascade. Once the inflammatory cascade turns on it promotes itself. Inflammation turns on inflammatory reactions creating its own vicious cycle. Treatments should not just focus on brain inflammation; the digestive tract inflammation also needs to be addressed and vice versa. Comprehensive treatments should address the vicious cycle of digestive tract inflammation, brain inflammation and improving vagal nerve function as well as communication.

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