Gut-Brain Axis – What It Is & Why It Matters


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Written by Phillippa Quigley

Do you ever associate your digestive system with your brain? They’re two completely separate body parts, right? Wrong. The gut and the brain are incredibly highly connected. It’s called the gut-brain axis, and here we explain how important this unison is to our health.

“All disease starts in the gut” – Hippocrates

More and more ‘gut health’ is being talked about as being a prime part of our overall health. People are starting to understand that looking after our gut microbiome is really important.  

The gut microbiome refers to all the tiny microorganisms and natural bacteria that live in your intestinal tract. These microorganisms and the bacteria are critical to your health.

The gut-brain axis is an element of our health that is gaining interest as being an integral part of how our body works.

This article will discuss what the gut-brain axis actually is, how it works, and how we can look after it.

Gut-brain axis explained

How often have you heard the saying ‘follow your gut’, or ‘I had a gut feeling that would happen’? These are so commonly used, as well as knowing the butterfly feeling in your stomach. Have you ever stopped to wonder what causes them?

diagram explaining Gut and Brain Connection

The feelings that you get suggest that there must be some form of communication or connection between your brain and your gut.

It is that communication that is going on that is given the term gut-brain axis. The brain and gut are both physically and chemically connected. It is this gut-brain connection that links your central nervous system (CNS) in your brain with the enteric nervous system (ENS) in your gut.

If we are hungry, then our brain will release the juices in our stomach before the food is even digested, showing that is a direct link between the two. This relationship goes both ways. If we are experiencing stress, anxiety or depression, then it can cause distress in the gut as well.

Ideally we want our gastrointestinal system to be in a state of homeostasis. Thus, meaning balance. Our gut is an incredible organ, responsible for many important roles within the body.

What does our Gut do?

Our gut helps our body work. It helps break down the food we eat, produce energy, absorb nutrients, aids hormonal balance and eliminates waste and toxins from the body.

It is far beyond just digesting foods, and being responsible for flatulence and bowel movements!

Did you know that our gut houses 70% of our immune system? That itself tells you how much we should prioritise our gut health and ensure that it is in a healthy state. It also explains the meaning behind the quote by Hippocrates, at the start of this article. That being, that diseases and illnesses can start within an unhappy gut.

Our gut can tell us if it isn’t happy, if it is in disharmony or there is perhaps a malfunction going on somewhere in the body. However, it isn’t always that easy to understand what is going on, as the gut does not exactly spell it out.

The gut uses its functions to help communicate what it needs. For example, ‘tummy rumbling’ for hunger, and perhaps a slight contraction pain to signal you to head to the bathroom.

Let’s take a look at how the gut communicates possible disharmony.

Bathroom frequency

We can’t talk about the gut without talking about bowel movements. There is no ‘set’ routine which is the right amount of times a person should go to the toilet. Every person’s gut is different and what is important is that your gut has its own consistent pattern. This could be three times a day to four times a week.

So when this pattern is out of sync, and perhaps you haven’t been for days or maybe you cannot get off the toilet with diarrhoea, then this is your gut telling you something isn’t quite right.

If you suffer with constipation, you are holding onto waste for a longer time. Your body will reabsorb the toxins it is supposed to be expelling. This will create health implications if it is continuing to happen. It also shows that the digestive system is sluggish and not able to function correctly.


Our gut is responsible for producing neurotransmitters that are responsible for our mood. Neurotransmitters are chemical messengers for the brain. They help our brain control emotions and feelings.

If we are not consuming a diet that allows our gut to be able to produce these neurotransmitters, then our mood can be affected negatively. Therefore, causing mental health disorders. Conversely, if we consume a diet rich in vitamins, minerals and other nutrients it can act as a real mood booster.

We produce many of these neurotransmitters within our gut microbiome. Serotonin, which is known as the happy hormone, is largely produced in the gut. Gamma aminobutyric acid (GABA) is responsible for anxiety, and is also produced by the microbes in your gut.

This makes it very clear that a healthy gut is good for our brains. If we are not looking after our gut microbiome, then this makes it harder to produce neurotransmitters needed for a healthy mind.

If you are suffering with any mental health disorder, then addressing your diet might help ease your symptoms.


We need to be eating foods that we can digest easily, and foods that give our bodies much needed nutrients.

If we eat ultra-processed and sugar-rich foods, it will create an unhealthy gut microbiome, and also cause sugar spikes. Collectively, this will cause us to suffer with fatigue.

A healthy diet supplies you with energy and gives you a boost to be active and feel uplifted. A sluggish digestive system, on the other hand, will be reflected in your body and mind as it works hard to digest unhealthy foods.

Focusing on foods that are rich in Vitamin B will help give your body energy.

How do the brain and gut communicate?

The brain and gut communicate through the vagus nerve. This is a large nerve in the body which runs from your brain to your colon.

Your brain, central nervous system (CNS) and gut all contain neurons. Neurons are cells that basically tell your body how to behave. Your brain contains nearly 100 billion neurons, and your gut contains almost 500 million.

Gut brain axis as intestinal and nervous system interaction outline diagram

All these neurons are constantly travelling up and down the vagus nerve. The neurons will feedback information from the intestines to the brain, and will project any stress response to the gut.

The vagus nerve plays a role in the parasympathetic nervous system. The parasympathetic nervous system creates the opposite response to fight and flight. This is known as rest and digest.

The fight and flight stress response is well known for when our body responds to a perceived danger. Our heart rate increases, while our digestive and immune systems shut down to help our body prioritise the danger response. We also release a high amount of the hormones; cortisol and adrenaline.

When we are in a rest and digest state, our body and mind are in a calm state. We can digest our food, our stress response is low, and our immune system is operating in an optimal way.

It has been found that individuals suffering from irritable bowel syndrome (IBS) – a common bowel disorder which affects the stomach and intestines – have reduced vagal tone. When vagal tone is reduced, this means that the function of the vagus nerve is reduced.

Additionally, studies in animals have shown that when feeling stressed, the signals sent through the vagus nerve can cause problems within the gastrointestinal tract.

Both of these studies show that the vagus nerve plays an important role between your guts and your brain.

Healthy Gut, Happy Mind

So far, you can see how perhaps our gut health and mental health can influence each other.

Mental health conditions such as anxiety and depression can have an adverse effect on your gut; for example, causing IBS. When a person is feeling stressed, it can cause these conditions to ‘flare up’ and worsen. This in itself can trigger more stress.

As discussed before, when we are in a stress response our digestive system is not able to fully function. Therefore, to have our gut-brain axis operating optimally, we need to look after our mental health and gut health.

Let’s take a look at how to look after our gut-brain axis.

Gut-friendly diet

Eating a diverse and nourishing diet will help keep your gut healthy. You want to make sure you are eating enough fibre, and that the foods you consume are colourful.

illustration of brain filled with healthy colourful foods to explain gut-brain axis

A popular topic at the moment is probiotics and prebiotics. These are very gut-friendly and will help boost your gut microbiome. Our gut is full of bacteria (around 50 trillion!) and every person’s makeup of bacteria is unique. We need to make sure we keep it healthy.

Probiotics are fermented foods such as; kimchi, sauerkraut, kefir, miso and kombucha. These have live cultures which give your gut a healthy dose of good bacteria.

Prebiotics feed the bacteria in your gut and keep them strong. You can get prebiotics from plant foods such as onions, garlics, legumes, wholegrains, bananas, berries and many more.

It is worth noting that if you have recently been prescribed antibiotics or perhaps need them regularly, these will wipe out the bacteria in your gut. The good ones and bad ones! Therefore, think about adding probiotics and prebiotics into your diet to help restore balance within your gut microbiome.

How do you eat?

If you are someone who believes their gut is in some need of TLC, then you should also think about the way that you eat. Sounds a bit odd to consider how you eat, but it is really important. If you are working on your stress levels, and food is eaten in a frantic, rushed state, then you will not be aiding the rest and digest state you are wanting to achieve.

Everyone has probably done it at least once! That feeling of soreness in your throat after eating something so quickly, barely chewed, that you can feel it making its way down to your stomach.

If this sounds like you, try eating more mindfully. This is where you allow time to eat slowly without distraction, chewing your food more and allowing time for your body to signal it is full so that you do not over-eat. Also, engaging your senses as you eat and being more present in the moment will help your digestion.

This approach also has many other health benefits to your body, not just for your gut.

Reduce stress

We now know that stress and gut health conditions can come hand in hand. Tackling our stress is really important in helping our gut microbiome stay balanced and in an optimal state.

When you are stressed it can be hard to tackle the trigger of it all, especially if there are many factors involved. Therefore it is important to try and control what you can, and let go of those you cannot.

You can control what you eat and how you move your body. Here are some recommendations for reducing stress:

  • Simply move your body: This doesn’t have to mean hitting the gym, or completing a HIIT workout. In fact, workouts like a HIIT (high-intensity interval training) can actually make stress worse by increasing cortisol levels. You need to get active in some way, and if you can do it outside in nature, the benefits are even better.
  • Eat a varied diet: As mentioned before, a varied and colourful diet is good for your gut but also your mind. Eating highly processed foods and snacks with refined sugar will be no good for your body or brain. Nourish your body!
  • Meditate: Immediately this can put people off. The power of breathwork and meditation is hugely beneficial for reducing anxiety and stress, as well as helping your digestive system get into the rest and digest state.
  • Connect: Socialise with people that make you laugh. Talk to people and share your worries so that it doesn’t overwhelm you.
  • Prioritise sleep: Work on your bedtime routine to ensure it is calming and induces a healthy night’s sleep where you wake refreshed and restored.


It is clear that the gut-brain axis is incredibly important to our bodies. No longer can we see these two organs as separate entities. As the research is now showing, and as Hippocrates’ ideology showed over 200 years ago, the gut can be all-telling about our health.