Everyone’s gut microbiome is unique. HFM quizzed the experts about how this affects our mental health – and what we can do to look after it

The way to a man’s heart is through his stomach, or so the saying goes. But it turns out that the stomach may also be the way to a man’s head. Good gut health = good mental health.

Recent research has discovered that microbes in our digestive system may have an impact on our mental health. Scientists in Belgium found that people suffering from depression had low levels of specific gut flora (bacteria) called coprococcus and dialister, even if they were taking antidepressants.

The research, by the Flanders Institute for Biotechnology and the Catholic University of Leuven, analysed medical tests and GP records to look for links between mental health, quality of life and microbes in the faeces of more than 1000 people on the Flemish Gut Flora Project. The scientists also found that two types of bacteria – faecalibacterium and coprococcus – were more common in people who claimed to have good mental health.

‘The more we find out about gut flora, the more important it becomes,’ says dietician Dr Sarah Schenker. ‘I’d say it’s been neglected for decades, but it could be one way of explaining why there are so many differences between people’s health and wellbeing.’

‘The research is an exciting piece in the puzzle of our understanding of gut-brain interaction,’ agrees dietician Laura Tilt. ‘A lot is still unclear, but this new evidence supports existing data that shows the gut and brain are intimately linked, and can impact each other in terms of wellbeing.

‘The findings don’t “prove” that having low levels of certain gut bacteria causes depression – I think most of us acknowledge that depression is complex and has multiple causes. But they do show a change in the gut bacteria of people suffering with depression, which provides a possible target for therapy.’

And that’s the key. More research is needed, but these findings could open the door to new treatments for mental health disorders that use probiotics to increase levels of ‘healthy’ bacteria in the intestines. ‘Progress has been made by experts in the field and for some time now probiotics have been studied in relation to many things, but this research hasn’t come to the public attention because we’ve become cynical about probiotics,’ says Dr Schenker. ‘There is a suggestion that guts that aren’t protected by the right bacteria could be linked to autism, for example.’

Cause or effect?

There is a caveat to this research, in that the scientists themselves don’t yet know whether low levels of healthy bacteria in the gut is a cause of depression or merely a symptom of it. ‘It’s possible that people who have good mental health have other habits that help foster a healthy and diverse gut microbiome – eating lots of fibre, exercising regularly and having healthy ways of coping with stress – which may in turn positively affect the brain,’ says Tilt.

The gut microbiome is all of the genetic material in a microbiota, which is the entire collection of microorganisms – including bacteria, yeasts, viruses and fungi – in the digestive system. ‘Your microbiome is like a fingerprint that’s completely unique to you, and is influenced by many dietary and environmental factors,’ explains Tilt. ‘Unpicking the impact of these factors on mental health versus, say, genetic predisposition is extremely complex.’

‘Another problem is that down the years we have taken antibiotics as if they’re Smarties, and that’s an issue because they can wipe out gut flora that we may struggle to restore,’ adds Dr Schenker.

And there is evidence that gut health has an impact on the brain. Jeroen Raes, who led the Belgian research, also found in follow-up experiments that microbes help to produce neurotransmitters in the brain that can improve mental health. ‘We found that many gut bacteria can produce neurotransmitters or precursors for substances such as dopamine and serotonin,’ he reported. A lack of, or imbalances in, those substances have long been linked with poor mental health and depression.’

‘It’s estimated 70-90% of the body’s serotonin is made in the gut,’ adds Tilt. ‘That means there is potential for targeting mental health conditions indirectly by focusing on the microbiome.’

The probiotic potential

So probiotics may be able to help treat mental health conditions, but we’re still a long way from working out how. ‘The real sticking point is learning how we can influence gut flora, and that’s another area that will take a lot more research,’ says Dr Schenker. ‘Very few products on the market can make a real impact on this yet because they’re not strong enough. Trials are being done, independent of this new research, and future products may well show real benefits, but in terms of influencing things like irritable bowel syndrome and Crohn’s disease, let alone mental health, there’s still a long way to go.’ That’s not least because the manufacturers of probiotics, like the Belgian researchers, are learning more all the time. Gut health is a complicated science.

‘The manufacturers need to able to prove that their products work, as currently different brands have different strains of bacteria,’ says Dr Schenker. ‘We need to know a lot more – how they work, how they get to where they need to be and how they survive the digestion process. It’s not a simple process, and will take years.’

‘Some strains of bacteria have no effect on mental wellbeing, whereas others seem to be key players,’ Tilt adds. ‘Part of the challenge is not only deciphering which ones are the most important, but finding the right dose and the most appropriate and effective method of delivery.’

The Belgian researchers agree, pointing out that progress will rely on more research into bacteria to see what substances they produce before testing those and seeing how they are affected by specific probiotics – and that process itself is a precursor to human trials that may or may not prove a definitive link between gut flora and mental health.

‘Rather than focusing on how long it will take, perhaps we need to focus on the simple, inexpensive changes we can make to foster a healthy microbiome,’ says Tilt. ‘We know that diet has a huge impact, and those changes are relatively easy to make.’