Stress and the gut microbiome

Author: Leanne Mitchell, Accredited Practising Dietitian, Microba Microbiome Coach.

18 June 2020



Is stress overtaking your gut health?

The world is in unprecedented territory. Navigating through the uncertainty of the pandemic truly makes us value our health. However, above and beyond the health impacts, this uncertainty brings with it a lot of stress.  And stress can impact your gut health!

Brain to Gut: What happens to our gut when we are stressed?

When we are faced with a stressful situation our “fight or flight” mechanisms are activated.  This sends a flood of stress hormones into our bodies. The main stress hormones are cortisol and adrenaline. With these hormones flying around the body, our heart rate and blood pressure increases, so too does our breathing and blood glucose levels. Interestingly, our digestive activity is also decreased or changed. For some, this can mean digestive processes stop, and for others it results in an urgent emptying of the bowels. Whichever the outcome, it is clear that stress affects digestive function.

But beyond functional changes, stress can also impact the composition and function of the gut microbiome – the community of microorganisms living in our gut. Animal studies have found that stress can make the gut and intestines more permeable, activating immune and pro-inflammatory responses which trigger additional stress hormones to be released1.

A recent study found that when healthy pregnant women were subjected to a social stress test, their changing cortisol levels were associated with shifts in the types and numbers of bacteria found in their gut2.

This may help explain why scientists have found that people with stress-associated conditions, such as depression and anxiety, have gut microbiomes that are different to healthy people3.

A 2018 review found that depressed people had increased levels of bacteria that are associated with poor health (such as from the Proteobacteria phylum and the Eggerthella genus) while beneficial bacteria (such as from the Prevotella, Ruminococcus and Coprococcus genera) are decreased compared to healthy controls4.


Gut-to-brain: What does the research say? Read the blog.


Gut to Brain: Can supporting our gut microbiome help manage our stress?

Our gut can communicate with our brain via multiple pathways including neural, hormonal, and immune. The main neural connection is through the vagus nerve5.

The vagus nerve runs the length of our body, connecting all our digestive organs (such as our stomach and intestines) to our brain5.

This superhighway nerve allows the brain and gut to send signals to each other, however, most of the traffic runs in the direction from the gut to the brain5.

Serotonin, a neurotransmitter associated with mood and anxiety disorders, is one of the many substances that can activate the vagus nerve and send signals to the brain5,6.

Serotonin also plays a role in regulating our sleep, appetite and digestion and is therefore an important substance for our overall well-being7.

The majority of serotonin is produced in the gut by special cells which can be stimulated by the presence of the short chain fatty acids (SCFAs) butyrate and propionate6,7.

SCFAs are anti-inflammatory substances produced by gut bacteria that feed on prebiotic fibres found in plant-based foods8,9.

An animal study found that mice treated with SCFAs were able to better tolerate stress, showing less signs of anxiety and depression, than mice without this treatment10.

Of course, we are not mice, but this research indicates the role diet may play in our ability to manage and respond to stress, a role which is mediated by our gut bacteria!  Indeed, a recent study in healthy adults found that supplementation of a prebiotic fibre (B-GOS) was associated with reduced stress hormone (cortisol) response upon waking11.

So, diets high in prebiotic, plant-based foods may help improve your overall sense of wellbeing and increase your stress tolerance.

Our gut bacteria are also able to produce GABA, another mood-associated neurotransmitter. Low brain (central) levels of GABA are often reported in people who suffer depression12.

Animal studies have shown that the gut microbiome influences circulating and brain levels of GABA13, however, in humans it is unclear if the GABA produced by the gut bacteria impact on the levels in the brain.  Gut bacteria that produce GABA include Bacteroides, Parabacteroides and Escherichia species and a recent study found that levels of Bacteroides were negatively correlated with brain patterns associated with depression14.

Many studies have shown a link between diet and the risk for depression15, and this could be in part due to the ability of diet to shape and alter the gut microbiome.  A diet with increasing evidence for providing a benefit in depression is the Mediterranean diet16, a pattern of eating that is high in prebiotic, plant-based fibres.


Gut health brain health

Dr Pribyl explains the gut-brain axis. Learn more.


Practical strategies to help manage stress

The pandemic has certainly changed the way we live our lives. But as you assist your clients, why not use this also as a chance to start some healthy habits, habits that could also help you manage the stress associated with these uncertain times?

  • Gut to Brain strategies – fuel your microbiome through healthy eating.
    • Fill your plate with plenty of prebiotic, plant-based foods such wholegrains, vegetables, legumes, nuts and seeds!
    • Try going Mediterranean (or meat free) one or two days a week and enjoy large bowls of salad with legumes or roasted capsicum stuffed with zucchini and quinoa or baked fish with roasted vegetables.
  • Brain to Gut strategies – Find time for you….with no commute for many people, why not fill this “extra” time with:
    • Exercise – find an activity you enjoy or get on YouTube and follow along to a Zumba, circuit, or Pilates classes. You could also make a home gym or go for a run.
    • Do something that brings you joy – meditate, garden, draw, read or soak in the tub…quiet the mind and find something that tunes out the world.


About the Author


Leanne Mitchell, APD

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.


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