The Gut-Brain Axis Explained

Look after your gut and your brain

Understanding the gut brain axis can be complicated, that’s why we’ll explain and simplify the gut brain axis definition so that you can understand the effects it has on your immune system and mental health.

What is the gut-brain axis?

Studies show that your brain and gut communicate with one another through the ‘gut brain axis’.

How does it work?

Approximately 100 billion neurons are in the human brain and 500 million in your gut, connected to your brain through nerves. The vagus nerve is what sends the signals in both directions; one of the biggest nerves connecting your gut and brain.

Understanding the gut-brain axis

Vagus Nerve

One human study found that those with irritable bowel syndrome (IBS) or Crohn’s, had a smaller vagal tone which indicated that the vagus nerve wasn’t working at its full function. This suggests its level of importance in the gut-brain axis.


Neurotransmitters are what connect your brain and gut. A number of these chemicals are produced by your gut cells and all of the microbes living there. Your gut also produces 90% of your serotonin.

Gut Microbes

Gut microbes are able to metabolise bile & amino acids to produce a multitude of other chemicals that affect your brain.

A few studies found that in mice, stress & social disorders lower bile acid production by gut bacteria and even alter the genes involved in the production. Your gut microbe plays a significant role in your immune system and inflammation by controlling what goes into the body and what goes out.

Did you know that if your immune system is ‘switched on’ for longer than it should be, this can lead to inflammation? This is often associated with brain disorders such as depression & Alzheimers. 

How to improve your brain health via your gut

To improve your mental health, it’s important to introduce probiotics and prebiotics into your diet. Probiotics are live bacteria that can be very beneficial for your health.

Many cases show that probiotics can improve symptoms of depression, stress and anxiety.

Can apple cider vinegar help the gut-brain axis and mental health

Raw and unfiltered ACV, such as Willy’s, contains ‘pectin’. Pectin is a prebiotic fibre that is found in fermented apples, which aids good digestion by essentially getting rid of any excess cholesterol found in your gut. This prebiotic fibre is also key in encouraging the growth of good bacteria. 

As we now know the link between the gut and the brain, it’s easier to understand how a shot of ACV a day may help with your mental health. With a large proportion of serotonin being located in your gut, it’s important to ensure a healthy gut-friendly diet to maintain good mental health.

What foods are beneficial for the gut-brain axis?

Fermented foods (shown to alter brain activity) e.g. yoghurt, cheese and sauerkraut

– Polyphenol (increases healthy gut bacteria & can improve cognition) e.g. green tea, olive oil and cocoa

– Omega-3 fats (can increase good gut bacteria & reduce the risk of brain disorders) e.g. oily fish

– High-fibre foods (prebiotics can reduce stress) e.g. nuts, fruits and vegetables

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