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What is the Gut-Brain Connection

The gut brain axis is a two-way communication pathway between our Central Nervous System (the brain and spinal cord) and our Enteric Nervous System (which controls the function of the gastrointestinal tract/gut). Just like a highway connecting two cities, traffic, or in this case impulses/signals, can flow in either direction via the vagus nerve (a nerve extending from the brain stem to the abdomen [5]).  These extensive range of signals deliver essential messages to both the brain and the gut relaying information such as mood, immune response, digestion and heart rate [2].  Emerging studies suggest that the vagus nerve, the primary ‘highway’ connecting the gut to the brain, may actually be stimulated by the gut bacteria and respond by either enhancing mood or increasing anxiety [2]. The brain and gut are intimately linked.

On average, our microbiome consists of 1.8 kilograms of bacteria, and is often referred to as the second brain [4].  In fact, our gut houses more neurons (cells responsible for sending and receiving messages) than our brain, and actually sends more signals to the brain, than the brain sends to the gut [5].  This enormous selection of bacteria is responsible for our overall physical and emotional health and how we feel.  In fact, 95 percent of all serotonin (the happy hormone) is produced in the gut [4].   From immune system function, detoxification processes, inflammation responses, neurotransmitter activation, vitamin production, nutrient absorption, to signals of hunger or satiety and the utilisation of carbohydrates and fats, our microbiome is at the forefront [3].  Therefore, the health of your digestive system will directly impact the functioning of your brain.

Exciting studies exemplifying the gut-brain connection are rapidly emerging, further establishing that the presence of good bacteria in the gut alters brain function.  For example, a strain of bacteria known as Bifididbacterium longum has the ability to remove anxiety-like behaviour in mice, and certain probiotics have been found to reduce inflammation and increase tryptophan (an amino acid), a precursor to serotonin production, processes and chemicals involved in depression [5].  The inextricable link between the gut and brain is further demonstrated  by stress related psychiatric symptoms and gastrointestinal disorders like IBD (Irritable Bowel Disease) [5]. 

It is clearly established that good gut health is imperative to your state of mind and functioning body, and that we are able to change the messages sent between the gut and the brain by changing our microbiota.  Therefore, maintaining a well-balanced, complex array of beneficial bacteria is the key to mental, physical and emotional wellness and vitality, and the most effective manner to achieve this is through diet [3].



1.     Montiel-Castro, A. Gonzalez-Cervantes, R., Bravo-Ruiseco, G., Pacheco-Lopez, G. (2013).  The Microbiota-Gut-Brain Axis: Neurobehavioral Correlates, Health and Sociality.  Frontiers in Integrative Neuroscience. 2013 Nov 07 Doi: 10.3389/fnint.2013.00070

2.     Breit, S., Kupferberg, A., Rogler, G., Hasler, G.  2018.  Vagus Nerve as Modulator of the Brain–Gut Axis in Psychiatric and Inflammatory Disorders.  Frontiers in Psychiatry.  2018 Mar 13. doi: 10.3389/fpsyt.2018.00044

3.     Perlmutter, D.  Brain Maker (2015).  Little, Brown and Company, Hatchette Book Company, New York.

4.     Gedgaudas, N. Primal Body, Primal Mind (2009). Healing Arts Press, Vermont.

5.     Holmes, L.  Heal Your Gut (2015). Murdoch Books Australia, Crows Nest.