How stress can send our microbiome crazy!

According to a recent study, 85% of Brits experience stress regularly, with more than a third of us feeling stressed for at least one full day every week (1). Repeated stress heightens our sense of anxiety, fear and urgency and can quite literally destroy our long-term wellness.

This isn’t another article on the benefits of exercise for stress. Instead we are going to focus on a less-discussed topic: the effects of stress on our microbiome – the inner ecosystem of the gut. To put some perspective on this before we start, the cells in our body are outnumbered at around a 10 to 1 ratio by single-celled organisms (mostly bacteria) that primarily reside in our gut.

It has been proven that stress can not only deplete and compromise our microbiome, but it alone is enough to drill holes in our gut and send our microbiome crazy, to the point of failure.

So, let’s break this down…

What is stress?

According to the American Psychological Association (the largest scientific and professional organisation of psychologists globally), stress is any “uncomfortable emotional experience accompanied by predictable biochemical, physiological and behavioural changes” (2).

Stress is a sophisticated, intricate and complex psychological response. When you are stressed, you produce two main stress hormones known as norepinephrine (adrenaline) and cortisol (think of this chemical as a double-edged sword: too little and we have what is known as adrenal fatigue and we become too exhausted to function; on the other hand, too much and we become tired but constantly worried and live in a constant state of anxiety).

Stress is beneficial in short sharp bursts and evolutionarily-speaking has allowed us to not only survive, but thrive, over many hundreds of thousands of years. Picture our ancient hunter-gatherer relatives hearing a lion creeping up to them. They would notice the stimuli and interpret the information, which in turn would release stress hormones, causing what is known as the “fight or flight” response, driving them to either fight the lion or flee from it, thereby increasing their chances of survival. We also have “good stress”, referred to by psychologists as Eustress (3), which also allows us to feel excited and is vital for a happy and wholesome life. If we did not have this type of stress, we would not feel motivated, becoming quickly bored with life and feel little need to accomplish any goals.

However, constantly feeling stressed - something that is increasingly becoming an issue in the modern age due to factors such as work pressure, lack of rest, relationship complexities, social media, chemicals in the environment and processed foods etc. - has taken what used to be an advantageous, psychological response to increase our chance of survival and turned it into a debilitating and even deadly condition. Stress is much like a seesaw.

What is the gut?

Your gut is everything from your mouth, oesophagus, stomach, the small intestine, the large intestine, the colon and the anus. It is here, at the epicentre of our bodies, that we find our microbiome – where trillions of micro-organisms and diverse bacterial communities live, working with (and sometimes against) our cells to keep us thriving. It is thought that 80% of our immune system lives within the gut, affecting almost every aspect of how we feel each day (4).

When we are in good health, in what we call a symbiotic state, around 85% of our microbiome is good, but we can easily lose this balance and fall into a dysbiotic state, where our microbiome begins to get infiltrated by bad bacteria. This can influence our good health in a plethora of ways.

Roles of good bacteria in the gut:

  • Soothe and regulate inflammation
  • Support our immune system
  • Enhance mental wellbeing
  • Promote absorption of nutrients and minerals
  • Stabilise glucose levels
  • “Fight” off bad bacteria and disease causing pathogens
  • Hormonal balance
  • Aid digestion.

Stress and the gut:

It is now known through multiple research studies that repeated stress can cause adverse effects on our healthy gut bacteria, compromising the integrity of our gut lining or our “gut health” and therefore affecting our ability to function on not only a physical, but also psychological level.

80% of neurotransmitters are manufactured in the gastrointestinal, or GI tract (5), and when we stress, we interfere with our guts ability to work in an optimal manner. Think of our immune system as our bodies surveillance system - determining what is friend and what is foe. When we stress, we distract this system from doing its job and it either misses certain issues or is hyper-sensitive towards other non-threatening ones. The body sends out alarms that inhibit it functioning normally. For example, beneficial neurotransmitters, i.e. dopamine (note that dopamine is made in the adrenal gland, but manufactured in the gut), GABA (a mellowing out type transmitter) and serotonin stop being produced, while other neurotransmitters, such as epinephrine (adrenaline) start being produced in excess.

Negative effects of elevated stress on the gut:

  • Brain goes into flight-or-fight mode, which can impact the blood flow to your gut, resulting in a lull in digestion
  • Bad bacteria increases, driving chronic anxiety as the body recognises the increase and stresses more
  • Diving deeper, an increase in bad bacteria also leads to further suppressing of good bacteria, resulting in a much more vicious self-perpetuating cycle. The Journal of Physiology and Pharmacology recently published a study showing that consistent stress negatively affects the amount and diversity of your good gut flora (6)
  • Sterilises the microbiome
  • Causes increased susceptibility to illness
  • Results in tiredness and even chronic fatigue
  • Can cause nutritional deficiencies.

5 Ways to Manage Stress:

Think of your body as a house on fire. Once you remove the stress drivers, the flames, you cannot rebuild the house without builders who lay the foundations. Our microbiome are these builders. Luckily for us, stress is manageable and our microbiome malleable. This means that once we become aware of our problems, we can start to implement a solution that will work towards reducing our stress and improving the health of our microbial. So, what small changes can we make to help manage our stress?

  1. Diet – we need to optimise our diet. Nourishing foods provide the solid foundation from which our body functions. Poor dietary choices can not only affect our self-esteem and mood, but will also fail to provide our body with the micronutrients it needs to thrive. When it comes to the gut, we should focus on foods that are high in prebiotic fibre (a type of fibre that the good bacteria feed off), with good sources including garlic, onions, leeks, asparagus, bananas and oats (there are many more!!).
  2. Resisting the urge to comfort eat when we’re feeling stressed – although doing this creates a release of dopamine that puts us in that “food coma” state, it doesn’t help the body create more dopamine and therefore is a short-term effect. Not only this, it doesn’t tackle the root cause of stress and how we can create sustainable results.
  3. Probiotics – consider taking supplement probiotics to help replenish good bacteria.
  4. Sleep – getting enough and of the correct quality sleep not only assists with us feeling better both physically and emotionally, but is also linked to improved gut health. It has even been found that a disturbance in your circadian rhythm can disturb the microbes, leading to a depleted, unhealthy microbiome. Always try to aim for 7-9 hours of sleep a night.
  5. Exercise – Moving both increases metabolism and the rate at which we break down cortisol. Furthermore, exercise can help clear our minds. Let’s look at this one further.

Benefits of exercise on managing stress:

Many people use exercise as a way to fight stress and they may well be hitting on the nail on the head, here’s why...

  • The rush of feel-good endorphins released by the pituitary gland during exercise can act as a major mood booster as well as moderating our appetite, releasing sex hormones and enhancing the functioning of our immune system.
  • Focusing on exercise for an hour can help us forget about daily irritations or worries – you’re likely to feel much more optimistic after thinking about something else for a while, instead of dwelling on what has caused your stress and getting caught in a negative cycle of thoughts.
  • What’s more, with practise, you’ll see yourself making improvements, which is a great confidence-booster.
  • It is a good way of releasing built up tension or anger.
  • Not surprisingly, meditation or yoga is also a common strategy to reduce stress because of the wide range of emotional and spiritual benefits that it brings. Mindfulness encourages living in the present moment, acknowledging the emotions you’re feeling and taking the time to zone in on a feeling that you want to commit to. Gratitude also plays a large role in mindfulness and it is important we remind ourselves of the things in life we are grateful for. Dedicating even just a small amount of time to acknowledging and appreciating the positive can help you find the strength to deal with the negative.

Exercise and meditation are two great ways to combat stress, but the most important thing is to find something that works for you and above all else, be kind to yourself.


1. Forth with Life, 2018, “Stress Statistics UK 2018: Great Britain and Stress”, URL:
2. Baum, A., 1990, "Stress, Intrusive Imagery, and Chronic Distress," Health Psychology, Vol. 6, pp. 653-675.
3. Glei DA, Goldman N, Chuang YL, Weinstein M., 2007, “Do chronic stressors lead to physiological dysregulation? Testing the theory of allostatic load”, Psychosomatic Medicine November.
4. Venter JC, Adams MD, Myers EW, et al., 2001, “The sequence of the human genome”, Science, 291:1304–1351.
5. Dinan, T.G; Cryan, 2015, "The impact of gut microbiota on brain and behavior: implications for psychiatry", Curr Opin Clin Nutr Metab Care, 18: 552–558. doi:10.1097/MCO.0000000000000221.
6. Konturek, P. C., Brzozowski, T., & Konturek, S. J., 2011, “Stress and the gut: pathophysiology, clinical consequences, diagnostic approach and treatment options”, Journal of physiology and pharmacology: an official journal of the Polish Physiological Society, 6, 591–599.
7. Levine, B., 2018, “National Stress Awareness Month”, URL:
8. Anxiety and Depression Association of America, 2018, “Physical Activity Reduces Stress”, URL:

Published on 25th Oct 18