Why Does Traumatic Brain Injury Harm Your Gut?

The aftermath of a traumatic brain injury (TBI) can be frustrating. Years later you may struggle with remembering, or learning new things. It can be hard to keep yourself organised or to even make decisions. And the mood swings are especially hard. Your TBI may be having an effect on your digestion – thanks to the gut-brain axis.

The aftermath of a traumatic brain injury (TBI) can be frustrating. Years later you may struggle with remembering, or learning new things. It can be hard to keep yourself organised or to even make decisions. And the mood swings are especially hard.


Your TBI may behaving an effect on your digestion – thanks to the gut-brain axis.


The good news? The relationship between your gut and your brain can help you in reducing your symptoms.

What Is the Gut Brain Axis?

Often the way in which western medicine is organised can make you think of the various parts of the body as quite separate. After all, you see a cardiologist for your heart, a neurologist for your brain, and a chiropodist for your feet! But while we often treat ailments separately, your body is an incredible structure, made up of intertwined systems, and it’s always changing.


One nickname for the gut is the second brain. How many times in your life have you had a “gut feeling”? Did you always heed it? It’s something you should take seriously –your gut and brain are in constant communication with each other.


Not only do the walls of your intestine contain neural tissue, but they make up to 95% of your feel good hormone, serotonin. And the vagus nerve, which is the longest cranial nerve in the human body, transmits information from the brain down to your gut – and vice versa! This communication network is called the Enteric Nervous System (ENS), or gut-brain connection.


The silent partner in your gut-brain connection is your gut microbiome. The gut microbiome is crucial to good gut health. Made up of colonies of bacteria that aid you in breaking down nutrients and providing useful digestive enzymes, when your gut microbiome is balanced, it’s a mutually beneficial relationship. Your gut microbiome can communicate with your brain through the gut-brain connection to influence food cravings. However, this two-way relationship is very sensitive to stress and changes in diet. Traumatic brain injury and the effect on the brain-gut axis is a hot topic for researchers and scientists.

How Are Traumatic Brain Injury and Intestinal Dysfunction Connected?

Experiencing a brain injury can have vast ramifications on the rest of the body, including interfering with immune system function, through disruption of the autonomic system. Your autonomic system is the part of your nervous system responsible for regulating bodily functions you don’t have to think about – for example, heart rate, sweating, or pupil response. The autonomic system also controls gut movement and digestion – and there is a clear link between autonomic dysfunction and irritable bowel syndrome.

Meisel C, Schwab JM, Prass K, Meisel A, Dirnagl U. Central nervous system injury-induced immune deficiency syndrome. Nat Rev Neurosci. 2005 Oct;6(10):775-86. doi: 10.1038/nrn1765. PMID: 16163382.


But traumatic brain injury has also been connected to poor gut health in the following ways:


  • TBI can cause an increase of noradrenaline in your system, a fight-or-flight neurotransmitter that can slow down digestion and regulate the gut-brain axis. In a mouse study it was discovered that the high levels of noradrenaline caused by TBI has an adverse effect on the gut microbiome. Patients with TBI can experience stomach pain, bloating, constipation, or ulcers in the gut, thanks to these changes.


  • In animal studies, TBI can increase intestinal permeability. Increased intestinal permeability (also known as leaky gut) means you have a compromised intestinal wall. Where your gut wall would normally only allow water and nutrients through, when you have leaky gut, the gaps in your gut wall are much larger – and waste     products and larger particles can get through into your bloodstream.    Consequences include an inflamed gut, resulting in inflammatory bowel disease, Celiac disease and the potential for other autoimmune diseases.


  • The above results in inflammatory issues in both gut and brain, a compromised gut mucosa, and blood-brain barrier permeability. In mice, one study found that TBI had a major effect on the structure and function of the gut, and the resulting imbalance in the gut microbiome may contribute to neuro conditions and have an adverse impact on TBI. This study is notable because it shows long-term changes in the intestine, which can take weeks after the original injury to manifest.


  • Gastrointestinal dysfunction and an unhealthy gut microbiome also occur after a stroke, thanks to the gut-brain connection, and this can have an effect on recovery.


So: your brain and your gut have a connection that can be impaired in the wake of a traumatic brain injury. Scientists are now exploring therapies that may aid the healing of both brain injury and gut health, such as probiotics, vagal stimulation, and dietary changes. Neurofeedback, in particular, is a great therapy that can help heal TBI, and we also recommend acupuncture as a way to stimulate the vagus nerve and restore gut mobility.  Dietary and nutritional changes target the gut microbiome and have the added benefit of being something you can control. But how does this research help you right now?

What Does This Research Mean for Mild Cognitive Impairment and Dementia Patients?

The discovery that traumatic brain injury can cause problems in the gut is crucial, because it shows the importance of the gut-brain axis and the gut microbiome. Even more excitingly, it underlines the importance of good gut health in the recovery of cognitive function. The bi-directional inflammation is one of the contributors to Alzheimer’s disease – and according to a mouse study, a traumatic brain injury may increase your chances of developing Alzheimer’s. Whether you have mild cognitive impairment, Alzheimer’s disease, or a traumatic brain injury – the Bredesen protocol could help you.