The gut and the brain share plenty in common. The enteric nervous system (ENS) of the gut can function independently of the two main branches of the autonomic nervous system and collects information from the outside world (via ingested food), just as the brain does from our sense of sight, smell, hearing, taste and sensation. The ENS runs from oesophagus to anus, and controls digestive reflexes, although it is influenced by the actions of the sympathetic and parasympathetic nervous system.

Many people suffering from mood disorders also suffer from gut disturbances. Digestive processes can be altered by stress and emotional states, causing symptoms such as bloating, pain, cramping, constipation, diarrhoea and nausea.

How do the brain and microbiome communicate?

The discovery of the microbiome and its potential contribution to brain health has revolutionised the treatment of mood disorders. Many experts classify the microbiome as a organ unto itself, a living organism that exists synergistically within the human body, extending even beyond the gut. Areas of the body previously thought to be sterile are now known to contain symbiotic bacterial colonies, including the urinary tract and uterus. Communication between beneficial micro-organisms and the nervous system has contributed to the discovery of the gut-brain axis and opened up avenues of treatment previously not thought possible.

Two way communication between the gut, brain and microbiome occurs via the vagus nerve with the help of serotonin, acting as a signalling molecule. Serotonin is well known for its function in mood and is the target of primary treatments for depression. The microbiome also communicates with the immune system, helping to reduce reactivity, inflammation and promote barrier integrity (protecting against leaky gut). It is also known to have a direct impact on the hypothalmic-pituitary-adrenal axis which controls our stress response, the dysfunction of which is linked to depression and other mood disorders (5). In animal studies, impaired stress response and cognitive dysfunction has been noted in mice rendered sterile of all gut bacteria (1).

Depression, anxiety and the microbiome.

Many people are surprised to learn that up to 90% of all serotonin is produced within the digestive system by beneficial bacteria. Other neurotransmitters such as gamma-amino-butyric acid (GABA), noradrenaline and dopamine can also be synthesised by micro-organisms in the gut and are essential for mental health (3). Unfortunately, poor diet, untreated gut conditions and digestive inflammation may result in dysbiosis, or an imbalance within the microbiome itself. This, in turn, is likely to have an effect on neurotransmitter production and mood. Studies show that gastro-intestinal inflammation can result in anxious or depressive behaviours that improve when treated with certain strains of probiotics (2, 5).

Unfortunately, nutrient deficiencies caused by insufficient dietary intake or digestive dysfunction are common. Correcting these deficiencies is a vital step in making sure that the brain and gut can produce sufficient quantities of neurotransmitters, regulate inflammatory processes and support neural biochemistry.

Personalised nutrition supports gut and brain health

Nutritional psychiatry is an emerging area of study that uses food and specific nutrients to bring about effective change for those suffering from mood and other mental health disorders. As nutritional deficiency has a substantial role in the pathogenesis of many types of disease, it is reasonable to expect that conditions affecting the brain may also have a similar basis.

Using personalised nutritional protocols, it is possible to assess and correct dietary deficiencies based on symptoms, current food intake, and potential nutritional gaps. Addressing gut health is an important part of this process. Recurrent gut issues are corrected first to assist absorption of minerals and reduce risk of symptoms reappearing further down the line. Nutrients known to enhance brain health such as magnesium, zinc, B vitamins, essential fatty acids, methyl donors, probiotics and amino acids can be included within dietary plans, or supplemented if necessary.

Eating a diet primarily of wholefoods, reducing sugar and gluten, and removing processed foods from the diet supports the function of the microbiome and gut health as a whole. Environmental toxins such as pesticides, herbicides, cleaning chemicals and pollution have a detrimental effect on both gut and brain health and should be avoided where possible. It must also be considered that mental health is certainly not just about physical wellbeing; it is an intricate and delicate balance between psychosocial and emotional wellbeing too, and this should be addressed by a supportive and qualified practitioner where possible, to ensure a holistic approach.

To find out more about the connection between brain, gut and microbiome, or to discover how personalised nutrition can benefit you, please feel free to contact us.


(1) Longitudinal, S., Structural, M., & Models, W. (2015). Neurotransmitters: The critical modulators regulating gut-brain axis. J Cell Physiol, 2(2), 147–185. https://doi.org/10.1515/jci-2013-0007.

(2) Zhu, X., Han, Y., Du, J., Liu, R., Jin, K., & Yi, W. (2017). Microbiota-gut-brain axis and the central nervous system. Oncotarget, 8(32), 53829–53838. https://doi.org/10.18632/oncotarget.17754

(3) Zheng, P., Zeng, B., Zhou, C., Liu, M., Fang, Z., Xu, X., … Xie, P. (2016). Gut microbiome remodeling induces depressive-like behaviors through a pathway mediated by the host’s metabolism. Molecular Psychiatry, 21(6), 786–796. https://doi.org/10.1038/mp.2016.44

(4) Liu, R. T. (2017). The microbiome as a novel paradigm in studying stress and mental health. American Psychologist, 72(7), 655–667. https://doi.org/10.1037/amp0000058

(5) Foster, J. A., & McVey Neufeld, K. A. (2013). Gut-brain axis: How the microbiome influences anxiety and depression. Trends in Neurosciences, 36(5), 305–312. https://doi.org/10.1016/j.tins.2013.01.005

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