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Anxiety, Depression and the Gut Microbiome

Have you ever wondered what the link is between the gut microbiome and psychological conditions, such as Anxiety or Depression? Well you are in the right place. I'll explain just how our thoughts and emotions can create gastrointestinal upset, as well as how issues within our gut microbiome have been linked to our brain function and how we think. I know - It's a crazy thought isn't it!

Major Depressive disorder is one of the most common mental disorders worldwide. While we still have so much more to learn when linking the gut to the brain, we do know that the gut brain connection is a real thing and we call it the Gut-Brain Axis. This gut-brain axis is conducting bidirectional communication all day, every day, meaning that not only does our brain send important messages to our gut, but the gut also talks to the brain, effecting our brain function (our mood, thoughts and even our memory).

So let's start with how our brain talks to our gut and cause gut symptoms. Have you ever felt butterflies in your stomach when you feel a little nervous? Or perhaps it is a "gut wrenching" experience that made you feel physically ill to your stomach? It's easy to see here that our brain really is sending messages to our gut. The information that our brain collects from the outside world through sight, smell, taste, hearing and touch is gathered and sent to the rest of the body so that it can do something about it.

It is here that the link between stress and the symptoms of IBS such as bloating, diarrhoea, constipation become evident. People who have IBS have super sensitive nerves surrounding their gastrointestinal tract, so when they become stressed, it sends signals down to the nerves in the gut, exacerbating IBS symptoms. They will often find it helpful to find ways to destress - meditation, gentle exercise or using Gut-Directed Hypnotherapy are all great ways to calm the brain, which in turn calms the gut and reduces IBS symptoms.

So what about the gut and how it can affect our brain function? I will first talk about the gut microbiome, so that you can better understand how it affects our brain.

When we talk about gut health, we are really talking about the gut microbiome. The gut microbiome is made up of trillions of microorganisms and genetic material that live in our intestinal tract (mostly in our large intestine). This microbiome is mainly bacteria and these bacteria are involved in functions critical for our health and wellbeing. They play a role in digestion of food, and assist in absorbing and synthesising important nutrients, assist in metabolism, regulate body weight and immune regulation, as well as brain function and mood.

Gut microbiome and Anxiety/Depression

So the bacteria in our gut have many the important roles within the body for optimal functioning - I want to talk now specifically, on how recent evidence shows how the bacteria in our gut may affect our brain function and how the bidirectional communication between the gut and the brain may play a key role in maintaining brain health.

While research in this area is really still in its infancy, they have come a very long way in finding how gut bacteria affect our psychological well-being. In recent years, the gut microbiota has been found to be essential in immune and metabolic health and also seems to influence the development of diseases of the Central Nervous System like behavioural disorders and neurodegenerative disease.

How do they do this? Bacteria in our gut have been found to produce and/or consume a range of neurotransmitters such as serotonin, norepinephrine and Gamma-aminobutyric acid (GABA). The brain uses these neurotransmitters to regulate basic physiological processes and mental processes such as learning, memory and mood. For instance, 95% of the body's serotonin, which influences our mood is found in our gut.

But there are several neurotransmitters that play a role in disorders of the brain:

Serotonin - Most of which is found in the gut, modulates human behavioural processes including mood, perception, reward, anger, aggression, appetite and among others, memory. Dysregulation of serotonin and serotonin receptors have been implicated in the pathophysiology of Major Depression and suicide and hence have been the target of treatment for nearly all neuropsychiatric disorders (1)

Dopamine is one of the major neurotransmitters that are involved in decision making, attention, memory and reward motivated behaviour. Alterations in the gut microbiota have been linked to dysregulation in the Dopamine system and pathophysiology of several neuropsychiatric disorders (2)

Norepinephrine which is responsible for arousal, alertness, behaviour and cognition as well as a precursor for norepinephrine, epinephrine, appear to be produced by and/or affected by bacteria in our gut. Low levels of this hormone have been shown to play a role in ADHD, depression and low blood pressure (3)

GABA is a neurotransmitter that is also a mediator in the enteric nervous system controlling GI function. It is also involved in immune cell activity associated with different systemic and enteric inflammatory conditions. Deficits of GABA are common abnormalities observed in major depressive disorders

While most of the current evidence comes from studying rodents, initial studies in humans have shown that the gut microbiome can influence neural development, brain chemistry and behaviour

How does our Gut Microbiome Develop?

There is evidence to suggest that our gut bacteria begins when we are still in the womb. when we are born there are many factors that influence the number and type of bacteria we have. Factors such as the type of birth (vaginal or cesarian), breast or bottle fed and as we grow things such as our diet, stress, medications such as antibiotics, illness and lifestyle will all change the bacteria that are living in our intestines.So what is considered a "Healthy Gut"

Despite all the research, we can't pinpoint exactly what a healthy gut looks like. This is because of the trillions of different types of bacteria - We have not been able to identify them all, as well as the fact that each persons bacteria is completely different and individualised. What we do know is that each different bacteria has different jobs - some may assist in fighting infection, while others perform digestive functions, or synthesising nutrients that help our body to function optimally. What we do know is that diversity and abundance is the key. With diversity we are more likely to have the specific bacteria that can complete all the important functions our body needs to thrive.

What Factors Influence Gut Microbiota?

There are many factors that can create an imbalanced microbiota (dysbiosis). Illness, stress, antibiotics or medications, poor diet, being overweight can all cause our gut microbiome to become unbalanced or disrupted which means our gut has limited ability to keep it functioning optimally and being able to perform all the tasks that are needed for optimal health.

How Can I Nurture a Healthy Gut

There are some things that you can do in order to increase both the number and types of bacteria that are residing in your gut.

Eat a variety of Fruit and Vegetables every day - The recommendation is to enjoy 30 different types and colours of fruit and vegetables every week. Fruit and vegetables are packed with nutrients but more importantly are packed with fibre, which our bacteria thrive on.

Probiotics - Probiotics add to the number and types of bacteria living in your gut, and are currently used in the treatment of mental health conditions, alongside any medicines prescribed by your doctor.

Antibiotics not only kill the bad bacteria in your body, they also get rid of the good. If you have been unwell or had to take antibiotics, it won't hurt take a probiotic supplement to boost your bacteria. You can also find probiotics in probiotic yogurt, kefir, miso, sauerkraut and tempeh.

Consumption of healthy omega 3 fats with Mackerel, Salmon, flaxseeds, chia seeds or walnuts - These have an anti-inflammatory effect on the body and are also great for heart health

More protein from plants and less from red meats - Ok - this really depends on how much of each you eat, but try and source more protein from foods like chick peas, quinoa and tofu

Reduce intake of takeaway foods, processed foods, cakes and pastries and saturated fats

Processed and takeaway foods can cause an inflammatory response in the body when consumed frequently.

More sleep - I know everyone is different in the amount of sleep they need. But generally make sure that you get enough that your not dragging yourself around all day - Sleep is also important for gut health

Exercise and Reduce Stress - Just like our diet has a big impact on gut health, so does exercise and stress. Aim to get out and do some exercised a few times a week and reduce stress with methods such as meditation, exercise, cooking or gardening - Choose what makes you feel good.

I hope this information helps you even a little. Remember, If you would like more individualised support to optimise your gut health, I am here to help.


  1. Berger, M Gray, JA and Roth B. The expanded biology of Serotonin. Annual Review of Medicine22 mar 2018

  2. Gonzalez-Arancibia C, Urrutia-Pinones J, Illanes-Gonzalez J, Martinez-Pinto J, Sotomayor-Zarate R, Julio-Pieper M, Bravo JA. Doo your gut microbes affect your brain dopamine? Psychopharmacology (Berl). 2019 May; 236(5):1611-1622. doi:101007/s00213-019-05265-5. Epub 2019 May 17 PMID: 31098656

  3. Strandwitz, P. Neurotransmitter modulation by the gut bacteria, NCBI - NIH 2018

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