Harnessing the gut microbiome: How can dietary interventions provide treatment and prevention for depression?

Author: Leanne Mitchell and Lilli Burdon

20 August 2020



One in seven Australians will experience depression at some point in their lives1, with 4.3 million people receiving mental health-related prescriptions in 20192. Of these, 50% of psychiatric patients discontinued psychopharmacological treatment prematurely3. As a healthcare professional, you see people with many complex conditions, some of which may be linked to their mental health. Could there be a more holistic method to reduce the prevalence and severity of depression that lies in the gut microbiome?


Lifestyle factors and depression

While there is no one specific cause of depression, there are a range of lifestyle factors that impact the onset of depression. Such factors include prolonged stress, sleep deficiency, isolation, limited exercise and poor diet4,5. Increasing evidence points to a link between diet and mental health, and there is great interest in the pivotal role that gut health plays.
As healthcare professionals would be aware, our gut microbiome is a community of microorganisms living in our large intestine. Each person has a unique microbiome which consists of an abundance of microbes that are influenced by genetics, age, medications and lifestyle factors6.  Arguably, one of the most significant lifestyle factors impacting the composition of the microbiome is diet6. The gut and the brain communicate via a bidirectional network relaying signals involving neural, immune, autonomic and endocrine systems, known as the gut-brain axis.


Does stress impact your gut microbiome? Read the blog.

How is the gut microbiome linked to depression?

The role of the gut microbiome in depression was first highlighted in a transformative study in which mice colonised with faeces from patients with Major Depressive Disorder demonstrated depression-like behaviours compared to the control mice7. Subsequently, human studies have indicated that depressed people show reduced gut microbiome diversity compared to healthy people8.
Interestingly, people who suffer from gastrointestinal conditions, such as Irritable Bowel Syndrome (IBS), have higher rates of mental illness9. In fact, both depressed people10 and those with IBS11 are known to have a hyperactive stress-response system (or hypothalamus-pituitary (HPA) axis).  HPA dysfunction can impact neurotransmitter activity, compromise immune and inflammatory processes and disturb the intestinal barrier function10.
The most established neurological change associated with depression is a reduction in neurotransmitter production, especially serotonin12. Serotonin is important for many regulatory functions involved with sleep, digestion, appetite and mood, leading it to be widely considered the ‘feel good hormone.’ An estimated 90% of the body’s serotonin is produced in the gut13,  with animal studies showing that serotonin or medication targeted to regulate serotonin levels (SSRIs) interacts with and alters the gut microbes14.
Further tests have revealed that the gut microbiota acting through short chain fatty acids increases the production of serotonin in the gut15,16. This highlights the importance of optimising gut health and mental health to support important functions such as serotonin production.


“Food as thy medicine” 

Food plays an important role in your gut health and overall health. The rapid adoption of the Western diet around the world promotes undernourished and overfed populations17. In Australia, foods high in energy and low in nutrients provide one-third of calories consumed by adults2. In addition, almost 90% of Australian adults do not eat the recommended number of daily serves of vegetables, missing critical nutrients and dietary fibres2.
A high-fibre diet has been associated with good health and mental wellbeing. The popular Mediterranean diet is a high-fibre dietary pattern characterised by a diverse intake of plant-based foods (green leafy vegetables, fruits, legumes, nuts, wholegrains) and a balanced intake of heart-healthy sources of animal proteins and fats (fish and olive oil). Accordingly, the Mediterranean diet offers an abundant intake of prebiotic fibres, antioxidants and omega-3 fatty acids and limits pro-inflammatory foods. Indeed, multiple studies have reported a reduced risk for depression or remission of symptoms in people following a Mediterranean diet18,19. Conversely, a Western, low-fibre diet (composed of red meat, refined carbohydrates and highly processed foods) is associated with systemic inflammation and increased depressive symptoms20,21. Taken together, this suggests dietary intervention as a promising treatment option in the management of depression and potentially other mental health conditions.


Are lifestyle interventions overlooked?

Changing the composition of the gut microbiome generates potential to alter and optimise health. Up to 30-40% of an adult’s gut microbiome can be modified during their lifetime with diet being one of the most influential factors22. Promising results from the SMILES trials show that a dietary intervention has the potential to be a cost-effective approach to treat people with clinical depression23.  Nurturing the gut with a diverse intake of prebiotic fibre is a cost-effective and potentially more sustainable approach to supporting mental health. 
Microba provides an empowering analytical tool to assess your unique gut microbiome. The results of your Microba Insight™ Report can help to implement dietary adjustments to maximise your health.


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About the Authors

Leanne Mitchell

Leanne is an Accredited Practising Dietitian and works as one of the microbiome coaches at Microba. Leanne has a developing interest in the clinical application of the gut-brain axis in gastrointestinal disorders, mental health and neuro-developmental conditions.



Lilli Burdon

Lilli is a Psychology Honours student, with an interest in the connection between the gut microbiome and mental health. 


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