We’ve long said that ‘you are what you eat’. Now, new research might help to prove it.

“Often with anxiety, it’s a mental state, but you'll have an upset tummy. We’ve known that forever, you could probably read that back to the ancient Romans,” Associate Professor at the National Centre for Epidemiology and Population Health (NCEPH) Brett Lidbury says.

“Now there’s the connection that’s been recognised as something that’s a primary interest to health.”

Associate Professor Lidbury, who conducts research into complex human diseases - was bought on board by Dr Linda Thomas, clinical psychologist and mucosal immunologist to assist her in her exploration of the gut-brain axis.

A disorder in the gut – a gut dysbiosis – can affect mental health and psychological functioning. Equally, psychological ill-health can affect the gut and cause gut symptoms.

Dr Thomas, who is also an NCEPH Visiting Fellow at The Australian National University, runs a specialised clinic called Gut Feeling, focusing on treating disorders of the gut brain axis. She says her interest in the field peaked after her daughter was diagnosed with coeliac disease, a condition caused by an immune reaction to eating gluten.

“My daughter, an ANU student, was getting increasingly anxious and finding it harder and harder to complete her studies,” Dr Thomas says.

“My qualifications allowed me to treat her condition effectively, and we saw her anxiety decrease”.

“The connection between gut disorders and mental health is common. We see it a lot in our clinic, people will present with either mental health conditions or with gut problems, and when we treat them together, we really get traction on their physical and mental wellbeing.”

Having met while at university in the 1990s, the two academics remained in touch before starting to talk about research in 2018, considering Dr Thomas’ clinical observations and how to investigate that.

What followed was a retrospective analysis of cross-sectional data collected through Dr Thomas’ clinic. By the end of the study, the two researchers had a sample size of 62. There are plans to repeat the study on a larger cohort.

Through machine learning they saw data patterns which showed how gut health affects personality traits and psychopathology.

“There’s something really interesting about the philosophy of science here, and that is Western science has finally accepted that the brain is connected to the rest of the body,” Associate Professor Lidbury says.

“There’s this Cartesian idea – ‘I think therefore I am’ – and that the brain was separate from the body.

“As biologists we’ve always understood, ‘yes, it is part of the body’, but it seems in the last 15 years there has been a genuine recognition that we have neurons in our guts, just like we do in our brain, and there’s a conduit of communication between those two organs, and of course, it makes sense.”

Dr Thomas says personality – not just mental health – determines people’s responses to their gut symptoms.

And interestingly, people who have irritable bowel syndrome (IBS) symptoms – bloating, constipation, diarrhoea – appear to have commonalities in personality.

“They had low frustration tolerance, low mood, poor tolerance for their gut symptoms, as well as their psychological factors,” she says.

“In the past week I’ve had someone tell me this is a ‘gamechanger’. That was the mother of a medical specialist.

“A lot of people have suffered long term, been to their GPs, who had tended to focus – not exclusively – as just being purely a gut disorder and prescribe medication to help with things like reflux or constipation, and it never really gets them across the line.

“Now we’re using very specific probiotics, and it’s helped not only in their psychological wellbeing and gut health, but also we’ve noticed impact on attention, cognition and for memory as well.”

For Associate Professor Lidbury, the study has been a perfect example of how medical research should be carried out.

“This is really valuable,” he says.

“What excites me is to take the experiences Linda has with her patients and investigate  those clinical observations and insights.

“As a medical researcher, that’s pure gold. How can we go and investigate that? These are real people, real events reporting real symptoms to a real clinician.”

• The research was featured in last month’s Digestive Diseases and Sciences Journal.