First thing’s first. When looking at the gut-brain axis we need to have a basic understanding of gut health. Every individual has a unique microbiome within their gastrointestinal tract which consists of trillions of different commensal organisms such as bacteria, viruses, fungi and more. These commensal organisms co-exist to protect their environment and keep their host healthy. Collectively they are known as the gut microbiome. Unfortunately, when there is a disruption to the gut microbiome, such as an overgrowth of an undesirable bacteria, this can cause inflammation to the gastrointestinal tract and this is where the brain can be influenced.

There are a few different ways the brain can be influenced by the status of an individual’s gut microbiome. One of those ways is directly through inflammation within the gut itself. This can lead to an increase in endotoxins known as lipopolysaccharides. When the gastrointestinal tract is in a state of disrepair these endotoxins can sometimes escape from the gut lining into the blood stream and this is known as Leaky Gut. As a result, there is increased inflammation in the body and this can cross into the brain causing damage. This increased inflammation to the brain can exacerbate conditions such as depression, anxiety and dementia.

Another way the gut and the brain are connected is through the creation of neurotransmitters. Several neurotransmitters such as serotonin, also known as our ‘happy hormone’ are created in the gut. If the gut is in a state of imbalance (also known as dysbiosis) there will be increased inflammation which can then downregulate the synthesis of these neurotransmitters, and lead to a decreased production of our happy chemicals! The gut is also home to short-chain fatty acids (SCFA) which are the end product of bacterial fermentation of certain dietary fibres. During a state of dysbiosis the production of SCFA is also reduced and this impacts the gut-brain axis as these SCFA are integral to release certain neurotransmitters such as serotonin.

Finally, the gut-brain axis does not simply move in one direction, it is bidirectional meaning the gut and brain are constantly in communication back and forth. The gut and brain are connected by our vagus nerve which is a component of our parasympathetic nervous system. Our vagus nerve is essential to digest food as it sends messages to our stomach to contract and release food into our small intestines to be digested. For optimum digestion we want our vagus nerve communicating in harmony with our gastrointestinal tract. This is referred to as optimal vagus nerve tone. Factors that can decrease this tone include inflammation and stress.

So, how can we improve our gut-brain axis?

The easiest way to do this is through modifying diet and lifestyle factors. Eating a diet plentiful in whole foods such as fruits, vegetables, legumes, pulses and wholegrains helps to reduce inflammation and increases SCFA production within your gut. Reducing or eliminating processed foods, foods high in saturated and trans fats, as well as alcohol and sugar-sweetened beverages can also have a big impact on improving microbial diversity within the gut. Finally, lifestyle factors such as reducing stress, increasing exercise and improving sleep may all also confer a benefit on gut health and thus mental health as well.