The Gut-Brain Connection
Trust your gut feeling
We have all heard and used expressions such as ‘trusting your gut feeling’ or ‘gut instinct’ or had ‘butterflies in your stomach’ when feeling nervous. The link between your gut and your brain is not just metaphorical. It actually exists. The gut-brain connection or gut-brain axis (GBA) describes the two-way link between your central nervous system (CNS; brain and spinal cord) and your digestive system.
Much like the brain, the digestive system contains a network of nerve cells which communicate via chemicals known as neurotransmitters. This enteric nervous system (ENS) controls your gastrointestinal system and is sometimes referred to as your second brain. While the ENS does communicate with the brain, it is also capable of functioning independently.
Why does the gut have its own brain?
Although our second brain cannot carry out any of the higher functions of our primary brain, such as mathematics or essay-writing, it is large and complex and manages the functioning of our digestive system. The ENS controls digestion - from swallowing our food, producing enzymes to digest and absorb vital nutrients, right through to overseeing elimination when we go to the toilet.
But why is our gut the only organ that requires its own brain? Is it just needed to manage digestion or does it have other more significant roles? This is currently a question still to be answered in full.
Most of our ‘happy hormones’ are found in the gut
The ENS uses neurotransmitters to communicate, many of which are identical to those found in the brain, such as serotonin, dopamine and acetylcholine. Serotonin is a neurotransmitter which helps regulate mood and feelings of happiness and in fact 90% of our serotonin is found in the gut.
So why is the link between the gut and brain important?
Irritation of the gastrointestinal system can cause changes in mood. The second brain can trigger emotional changes in people with digestive problems such as irritable bowel syndrome (IBS), constipation and bloating. This may explain why a significant proportion of people with IBS also suffer with depression and anxiety.
Looking after your digestive system = looking after your mental health
As our two brains communicate with one another, it makes sense that therapies that help one system will help the other. Therefore, therapies such as cognitive behavioural therapy (CBT) and hypnotherapy have been found to help manage common digestive disorders such as IBS.
Conversely this important gut-brain connection highlights the value of good digestive health to manage our mental health.
Friendly bacteria for your mental health
It seems likely that our second brain is not just there to oversee digestion of food. It is possible that this second brain is also there to listen to the many gut microbes which make up our gut flora or microbiome.
Recent research suggests that both pathogenic (disease-causing) and ‘friendly’ bacteria have an impact on the gastrointestinal tract and can signal to the brain to affect behaviours and cause mental health disorders. The mechanism by which this happens, however, still requires further research.
There does appear to be an interaction between the gut microbiome and the ENS (or second brain) given the association of dysbiosis (an imbalance of the gut microbes) with central nervous disorders (e.g. autism, anxiety and depression) and functional gut disorders.
The health of the microbiome can be improved by adopting a healthy diet, by eating pre-biotic foods and taking probiotic supplements.
Gastrointestinal health is the cornerstone of optimal health
The health of your gut is intricately linked with many other body systems, including your mental health. By targeting underlying gut health problems this can help manage many other health issues. Gut health is the cornerstone of your overall health. Your gastrointestinal system is needed for the digestion and absorption of nutrients required by every cell of your body and the elimination of waste products and toxins. But we are now beginning to understand that the gastrointestinal system has a much more wide-reaching impact on our health, including mental health.
Analysing your digestive health
Fortunately there are now many functional tests for digestive health such as stool tests, which provide a detailed analysis of digestion, absorption, inflammation, gut metabolites, the gut microbiome and identification of gut pathogens. As nutritionists, by investigating the health of the digestive system, we can not only target gut disorders and symptoms but also their far reaching effects on other body systems, including the brain.
Dr Sharon Pitt is a registered nutritionist at Nutrition First, with 18 years’ experience.
Nutrition First is a small and personal nutrition consultancy providing expert nutrition advice, based on sound scientific evidence.
At Nutrition First we help patients manage their digestive symptoms naturally and look at the connection between digestive health, mental health and other body systems. Contact us at Nutrition First to see how we can help you.