What does the gut-brain axis do? All the benefits of looking after yours

A green brain against a green background

Credit: Getty

Strong Women


What does the gut-brain axis do? All the benefits of looking after yours

By Lauren Geall

6 months ago

7 min read

Our brain and gut are intricately connected, which is why you get butterflies in your stomach when you’re nervous or feel a bit low after a course of antibiotics. Here’s everything you need to know.


Our ability to sense, heal, reproduce and experience emotions is so impressive that even the world’s most qualified doctors and scientists are still trying to wrap their heads around everything the body is capable of.

But of all the body areas of the body that have received increased research interest recently, the gut-brain axis has to be one of the most exciting. Over the last couple of years, studies have linked good gut health to improved blood sugar control, a strengthened immune system, better heart health and optimised hormonal balance. But when it comes to the gut-brain axis, researchers are only starting to scratch the surface of what is possible. 

One such researcher is Dr Emily Leeming, a microbiome scientist, dietitian and author of the new book Genius Gut: The Life-Changing Science Of Eating For Your Second Brain. The book, which explores all the latest research on the gut-brain axis and presents it in an accessible, easy-to-understand way, is packed full of useful content.

To give you a taste of what the book contains, we sat down with Dr Leeming to chat about the myriad benefits the gut-brain axis offers and the potential habits to avoid if you want to ensure you’re reaping them all.  


What benefits can nurturing the gut-brain axis offer? 

Before we dive into things, it’s important to remember that research into the relationship between the gut and the brain is still in its early stages. That means, for example, that scientists can’t say that having a certain type of good bacteria will help you think better – they just know there seems to be a link between the two.

Much of the research into the gut-brain axis has also been carried out in rodents, so we need to take the findings with a pinch of salt until they’re replicated in humans.

However, the research we have provides a basis for further research into whether specific interventions in the gut can have a direct impact on the brain, as well as a potential jumping-off point for people who want to support their health. 

1. Better focus and concentration

woman planning at work

Credit: Getty

Do you often find your mind wandering when you’re sitting at your desk or in an important meeting? Paying some attention to your gut microbiome could help you to concentrate more. Indeed, says Dr Leeming, while scientists aren’t exactly sure how the gut microbiome influences brain performance, they do know it’s a very real impact.

“We’ve seen some really interesting results in humans from certain probiotic studies,” she explains. “Certain probiotics have been linked to improvements in memory and brain performance, helping people to perform better on cognitive tasks.”

But this link between gut health and cognitive performance doesn’t just come into play when you consume a probiotic – it defines how well our brains work from a very early age. In fact, at just two years old, the make-up of our microbiome is linked to how well we’re able to interpret visual information (like recognising your favourite teddy bear) and our range of vocabulary, and by three years old it can influence your fine motor skills. 

Nurturing certain ‘good’ bacteria through adulthood – by eating plenty of fibre, exercising regularly and getting good sleep – can also make a difference to how we think. In a small study of young adults, those who had higher levels of certain ‘good’ gut bacteria were found to perform significantly better at mental tasks and found it easier to learn new information and problem solve.

Why is this? Scientists have their theories. “The gut microbes can talk to the brain directly through the vagus nerve, so that’s a very direct pathway,” Dr Leeming says.

“We also known that the microbes in our gut produce a really rich diversity of metabolites (a substance made when something, eg food, is broken down), including short-chain fatty acids. These short-chain fatty acids are specifically produced by your fibre-loving gut bacteria, and they’re important because they play a role in the health of your blood-brain barrier lining, which acts as a fortress to stop toxins entering the brain. So we think there’s both a direct and indirect role here.” 

2. Protection against dementia and other cognitive diseases

A yellow brain on a blue background

Credit: Getty

If having a healthy gut microbiome has been linked to mental clarity and concentration in the short term, can nurturing your gut have long-term consequences for your brain health too? “Absolutely,” says Dr Leeming.

“Some neurodegenerative conditions produce symptoms in the gut long before they do in the brain, which shows there’s a clear link,” she explains. “Patients with Parkinsons, for example, can have symptoms of constipation up to 20 years before diagnosis.”

A similar pattern can be seen with Alzheimer’s disease, Dr Leeming adds. Patients with inflammatory bowel disease (IBD) are six times more likely to develop Alzheimer’s than those without it, while those with gastritis are twice as likely.  

Rat-based studies have shown the knock-on effect the gut microbiome of a person with Alzheimer’s can have: when researchers transplanted those microbiomes into healthy rats, the rats’ brains became inflamed, they performed worse on memory tests and they had fewer neurons growing in their hippocampus (which is important for learning and memory formation).

But this relationship isn’t just a negative one – it could provide insight into potential treatments for neurological conditions, as well as ways for us all to protect our brains throughout our lives. For example, one study in mice found that when the microbiome of younger mice was transplanted into older mice, it reversed their age-related cognitive decline. Cool, right? 

3. Better nervous system function

Gut illustration

Credit: Getty

Studies show that the gut can play a powerful role in the production of neurotransmitters – ie the chemical messengers our brains and nervous systems use to communicate with each other, like serotonin and dopamine. But it’s not in the way you might think.

While many people cite the gut’s ability to produce serotonin (the feel-good hormone targeted by antidepressants) as one of the key factors in this relationship, Dr Leeming says this isn’t quite the case. “While it’s true that 90% of your serotonin is produced in the gut, serotonin can’t actually cross the blood-brain barrier because it’s too big, so it’s not going to have a direct impact on your mental health in that way,” she explains. “Instead, we think these neurotransmitters may have more of an indirect effect, by signaling to the brain through the vagus nerve.”

But the relationship doesn’t stop there. Perhaps most interestingly, researchers now think that the reason a healthy gut microbiome can boost mood (more on that later), is because your gut microbiome can influence how your body uses the building blocks of neurotransmitters, ie the compounds that make up serotonin and dopamine. 

“Your gut bacteria can help your brain to receive and access the building blocks of neurotransmitters like serotonin, including an amino acid known as tryptophan,” Dr Leeming explains. “One way they do this is by controlling the different ways these building blocks are used.”

In this way, Dr Leeming says, the gut microbiome can almost direct how much tryptophan is sent to different areas of the body, where it can be combined with other ingredients to make neurotransmitters and other compounds. An imbalanced or unhealthy gut microbiome can therefore lead to an imbalance in the amount of tryptophan that is sent to different places (and what it produces once it gets there) and have a knock-on effect on things like your mood and cognition. 

4. Mental health support

A relaxed woman breathing in in the sunshine

Credit: Getty

Talking about mood, your gut-brain axis can play a role in regulating your mood and mental health – which is why researchers are so excited about the role gut-based interventions could play in mental health treatment in the future.

“While there are many factors which go into a condition like depression, we can take learnings from research which shows there is a link between the gut and mental health,” Dr Leeming says. “And we’ve seen lots of evidence to establish that link.”

One of the key pieces of evidence, Dr Leeming explains, was the SMILES trial. This 12-week trial saw 67 people set out to measure how big a role diet – and the knock-on effect diet can have on gut health – could play on mental health. Over 12 weeks, those who followed the SMILES diet saw a “significantly greater improvement” than those who didn’t. 


Images: Getty

Sign up for workouts, nutritious recipes and expert tips, plus receive our 8-week beginner’s guide to strength training.

By signing up you agree to occasionally receive offers and promotions from Stylist. Newsletters may contain online ads and content funded by carefully selected partners. Don’t worry, we’ll never share or sell your data. You can opt-out at any time. For more information read Stylist’s Privacy Policy

Thank you!

You’re now subscribed to all our newsletters. You can manage your subscriptions at any time from an email or from a MyStylist account.