Head Injuries & the Gut

There are a couple of well known facts regarding things that are damaging to your gut health and they are: antibiotics; and stress. One that is often overlooked though is how a concussion / head injury can actually also cause gut dysbiosis even though these links were first mentioned ~90 years ago. In response to a head injury the body produces more noradrenaline which is essentially a fight or flight neurotransmitter that can slow down digestion as well as lead to an increase in gut permeability (“leaky gut”). Getting stuck in this fight or flight response following a bump to the head therefore promotes the same response as chronic stress – that is the system is unable to get into the rest and digest state in which it repairs itself.

What is unclear is how traumatic this brain injury has to be. Most of the population have taken relatively significant bumps to the head on such innocuous things such as leaving a cabinet door open and standing up underneath it. Any male growing up playing contact sports has certainly had numerous bumps to the head on the rugby or football field.

We have a nerve that runs from the brain down to our gut and has branches that go to our heart and lungs that plays a huge role not only in gut-brain communication but also system excitation and system calming. The functions of the vagus nerve can be broken down into 2 areas: sympathetic (excitatory) and parasympathetic (calming). The sympathetic side is involved with alertness, energy, blood pressure, heart rate, and breathing rate. The parasympathetic side is involved with blood pressure, and heart rate, and helps with digestions and keeping us calm and relaxed.

Following concussion and TBI changes in vagus nerve activity have been found which goes some way to explain why the system gets stuck in a state of fight and flight as the rest and relax response which is stimulated by the vagus nerve has become dysfunctional. Or rather following a neuro injury the individual’s system stays in a heightened state of alertness as there is an ongoing stimulus that overrides the vagus nerve function as the system is feeling continually threatened. Following head traumas and concussion changes in eye movements and eye tracking have been observed using RightEye tracking software that gives an insight into brain function. If an individual’s visual input is impacted (and the person will not necessarily even be aware of this) then this can be enough to keep the person in a heightened state and not allow their system to relax and repair itself leading to more problems over time.

Novel approaches have been developed to allow for the treatment of post concussive and TBI problems but access to them and especially to places that have software such as the RightEye system to measure changes remains a problem. This is just another thing that needs to be considered if someone if having ongoing gut health problems and nothing has worked – it could be that an old head injury is holding them back.