What Is The Gut-Brain Axis and Why Is It Important? 

By Eli Brecher | Jan 31, 2024 | 3 Min Read

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We’ve all experienced that feeling when we’re nervous: an upcoming exam, a presentation at work or even those butterflies in our stomach before a first date. This is the gut-brain axis at play.

Those “butterflies” show that our brain and digestive system are directly connected to each other, so when we’re stressed, our gut is affected too. This helps to explain why many functional gastrointestinal (GI) conditions, such as irritable bowel syndrome (IBS), are now recognised as disorders involving the the gut-brain interaction.

Let’s explore why the gut is our “second brain”, how the gut and brain are connected⁠, and what a “gut feeling” really is⁠.    

The gut-brain axis is the bi-directional (two-way) communication between the enteric nervous system (in the lining of the gut) and the central nervous system (the brain). The gut and the brain communicate with each other, sending signals in both directions – from the gut to the brain and from the brain to the gut. 


There are physical connections, such as the vagus nerve, as well as chemical connections such as serotonin (the “happy hormone”). Over 90% of our serotonin is produced in the gut – so when our gut health is not optimal, we struggle to produce that “happy hormone”, illustrating the clear link with our mental health


The two-way axis explains why stress can cause digestive problems, and why those with gut issues like IBS may experience feelings of anxiety and depression – because it works both ways.  

The gut is often referred to as the “ second brain” because it has a nervous system with more neurotransmitters than the brain’s central nervous system. 


When we feel stressed, our brain triggers the “fight-or-flight” response. This prepares the body to protect itself against danger by conserving functions that aren’t immediately necessary for survival, including digestion. 


The gut affects so many areas of our body typically thought to be controlled by the brain, from our mood and stress response to our immune system and our circadian rhythm (our natural sleep-wake cycles).  

The gut microbiome is the collection of trillions of bacteria, fungi and viruses is a key player in the gut-brain axis. The gut microbiome and the brain communicate via various mechanisms, including neurotransmitters and metabolites produced by gut bacteria, which communicate with the brain via the vagus nerve. The microbiome can also modulate immune cells in both the gut and the brain, impacting our immune system.
Deep diaphragmatic breathing is a simple technique to reduce stress and shift the body from fight-or-flight to rest-and-digest (the parasympathetic nervous system, where digestion is optimised). When we breathe in this way, our stomach expands with each inhale and contracts with each exhale. By activating the diaphragm, this “massages” our stomach and intestines, and so it can help minimise digestive symptoms such as abdominal pain and bloating.  

Practicing mindfulness and meditation activates the rest-and-digest response. A study of Buddhist monks found that meditation could help regulate the gut microbiome and also reduce the risk of anxiety and depression. We know that reduced stress levels goes hand-in-hand with optimal gut health, so these stress management techniques can be really helpful for supporting those with digestive issues.  


The impact of stress on the gut can be explained by the gut-brain axis. Interventions that reduce stress are now recognised as key tools in managing functional gut disorders such as IBS, as well as mental health disorders including depression. While it is inevitable that we all experience stress sometimes, using tools like deep diaphragmatic breathing and mindfulness can help mitigate the negative effects that stress can have on our gut health.  

Curious about enhancing your gut health? You can explore more insights and tips on our Nutrition Hub – your ultimate resource for nutrition wisdom and wellness.
The author of this article is gut health expert and registered nutritionist Eli Brecher (ANutr), who uses her expertise in the gut microbiome to build healthier habits. You can find more of Eli’s articles and her delicious recipes on our Nutrition Hub.