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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