The Gut-Brain Axis: How Your Gut and Brain Work Together

The gut-brain axis is increasingly mentioned, but what exactly is it and why is it so important? Your brain controls everything from your thoughts to emotions, but your gut has much more influence than you might think. The connection between your gut and brain is so strong that it directly impacts your physical and mental health. Here you will find everything about how this connection works, the role of cortisol, serotonin, and the nervous system, and how to keep your gut and brain healthy.

What exactly is the gut-brain axis?

The gut-brain axis is the communication channel between your gut and your brain. Through nerves, neurotransmitters, and hormones – such as cortisol and serotonin – they communicate with each other all day long. This axis is quite important: it determines how you handle stress, your mood, and how well your digestion works. One of the main players is the vagus nerve, a nerve that runs directly from your brain to your gut. This means that your gut influences your brain and vice versa.

Think about how cortisol is released during stress, which directly affects both your brain and your gut. This can manifest as abdominal complaints such as diarrhoea, cramps, or bloating. You may know the feeling in your stomach when doing something exciting like bungee jumping or meeting someone for the first time. Or the feeling that you suddenly need to go to the toilet right before an important moment like a presentation or interview. Conversely, your gut health also impacts your mood. An imbalance in your gut can lead to feelings of anxiety or depression. It's no wonder your gut is sometimes called your "second brain"!

The Vagus Nerve and Your Nervous System

In addition to your central nervous system (which includes your brain and spinal cord), you also have an enteric nervous system that plays a significant role. Your enteric nervous system is a kind of “gut brain” and is also known as the autonomic nervous system of your gut. It works mainly independently and communicates a lot with your brain via the gut-brain axis.

The vagus nerve plays an important role here and acts as a sort of highway over which signals are sent. These signals go both from your brain to your gut and the other way around: from your gut to your brain. In this way, your brain and gut are connected all day long and continuously send each other updates.

If your gut is out of balance, your brain receives a signal via the vagus nerve, which affects your central nervous system. You may then experience restlessness or feel less comfortable in your skin. Conversely, stress can affect your gut, making your gut more unsettled.

It's important that your vagus nerve works well so that the signals can reach each other properly. More and more studies show the importance of a well-functioning vagus nerve in conditions like irritable bowel syndrome (IBS) or Crohn's disease.

The Role of the Microbiome

Your gut is home to trillions of bacteria, fungi, yeasts, and other organisms, also known as your microbiome. These microorganisms help digest your food, support your immune system, and produce neurotransmitters like serotonin, which is also known as the “happiness hormone.” Serotonin greatly influences your mood, sleep, and is produced for as much as 90% in your gut!

A healthy microbiome is naturally important for good digestion, but also for your mood and mental clarity. Healthy gut bacteria help reduce inflammation in your body. Chronic inflammation is increasingly linked to mental problems such as depression and anxiety. If your microbiome becomes imbalanced – due to poor diet or stress, for example – this can also lead to lower serotonin production and more inflammation in your body. You may then experience more physical complaints, such as headaches, fatigue, or muscle pain, and also emotional dips.

Additionally, your gut plays a major role in your immune system. A large part of your immune cells is located in your gut. If your gut flora is out of balance, it can weaken your resistance. This not only makes you more susceptible to illnesses but can also cause brain fog. Read more about the microbiome here.

The Impact of Stress on the Gut-Brain Axis

Stress is one of the biggest culprits for your gut-brain axis. When you experience stress, your body switches to “fight or flight” mode and produces a lot of cortisol to better manage the stress. Cortisol not only has a direct impact on your brain but also on your gut.

When your body is too often in stress mode, it can cause an imbalance in your gut. A high cortisol level ensures that less blood goes to your digestion and fewer digestive juices (like stomach acid) are produced. When you need to fight or flee, digestion is not a priority. Your microbiome can be disrupted, and you may experience inflammation. Because everything in your gut works less well, you may experience bloating, constipation, or diarrhoea.

Inflammation also affects your mental health and how well your nervous system functions. Prolonged high cortisol can therefore also affect your memory and concentration and in the long term cause anxiety disorders or depression. Your brain functions less well, and you become more sensitive to stress. This can quickly lead to a vicious circle.

Stress is unavoidable in today's world, but it's important to regulate your stress. Find ways to keep cortisol under control - think of meditation, yoga, breathing exercises, and regular movement - to keep both your gut and brain healthy.

Serotonin: The Connector

The beneficial bacteria in your gut help you produce neurotransmitters like serotonin. Although the serotonin produced in the gut does not reach the brain itself, your gut sends a signal to your brain that everything is under control and running as it should.