GO WITH YOUR GUT
The future’s path to a healthy mind may go via your stomach
To nutrition-conscious foodies, the mind-gut connection is nothing new. But psychobiotics – a growing strand of neuroscience – is exploring the ways that feeding your microbiome could hold the key to combating mental illness
In the dark depths of my underwear drawer, behind the date-night bra and the grippy socks, sits a pack of pills. Popping one with my coffee is as much a part of my morning routine as the doublesnooze and the Radio 4 Today programme – it is muscle memory. They’re citalopram – an antidepressant I take for anxiety that, for the past few years, has made itself known whenever I’ve been looking the other way. I have no shame in the contents of my top drawer, but I’m becoming increasingly curious about the recent raft of research that’s exploring a new alternative – the likes of which I might find in my fridge. The latest frontier of neuroscience isn’t really about the brain – it’s all about the gut. The gut microbiome is now thought to be just as influential as our genes in determining who we are, and the study of psychobiotics – broadly defined as any intervention that affects the brain through the triggering of gut bacteria – is gripping the interest of researchers.
‘We’ve seen this area of research evolve so much over the past five years, driven not only by advances in technology, but also strong public interest,’ says Professor John Cryan, chair of the Department Of Anatomy & Neuroscience at University College Cork, principal investigator at the APC Microbiome Institute and co-author or The Psychobiotic Revolution (he’s basically the CEO of psychobiotics). ‘There’s huge excitement: people want to know what they can do with this information about how the gut influences the brain, and we’re struggling to keep up.’ Let’s, for a second, put a pin in this enthusiasm and back up a bit. The term ‘psychobiotics’ was first coined by Professor Cryan and his co-author, Professor Ted Dinan, to refer to the influence of probiotics – the bacteria found in foods like live yoghurt and miso – on the brain. It was the work of their team that led to the seminal study in this area, which has since been cited in research papers more than 1,000 times (science gone viral). In 2011, the team fed one group of mice a strain of the bacteria Lactobacillus rhamnosus, and another a bacteria-free broth. After several stress tests, the team observed an array of changes in the bacteria group, including alterations to neurotransmitter receptors in the brain, like GABA – the same receptor targeted by anti-anxiety drugs. They also observed a reduction in the anxious and depressed behaviour of the mice. ‘We proposed that if this could be reproduced in humans, it would lead to a psychobiotic effect,’ explains Professor Cryan. ‘And when we did some testing on healthy adult volunteers, the potential psychobiotics that we found did indeed have a significant effect in lowering stress response and changing brain activity.’
The definition of psychobiotics has since been broadened to encompass any intervention that influences the brain via the gut bacteria. As well as probiotic foods like yoghurt, this includes prebiotics – foods that feed your microbiome, like asparagus and leeks – as well as other interventions like exercise. The conviction with which the mindgut connection is spoken of would suggest that the brain and the gut are in constant communication, the likes of which you only witness in your most prolific group Whatsapp chats. ‘The body is so incredibly complex that there are many different mechanisms that could explain how the bacteria communicate with the brain,’ says Dr Megan Rossi (@theguthealthdoctor), research associate at King’s College London. ‘We do know that there are three main pathways. One sends messages through the bloodstream by producing chemicals in the gut; the second is through the nervous system; the third is like an alarm system, via immune pathways.’ While it’s one thing knowing these connections exist, proving how and why eating a yoghurt could make you feel less anxious is another challenge altogether. In 2013, researchers from UCLA used functional MRI scanning to prove that when healthy women ingested a probiotic twice daily for four weeks, it affected activity in regions of the brain that control emotion and sensation. More recent studies have explored the potential for manipulating this communication not only for anxiety treatment, but also for post-natal depression, schizophrenia and PTSD. Though human studies have been small so far, findings suggest that the implications of this communication extend far beyond our current comprehension. This could be huge. We’re in the midst of a mental illness epidemic – the number of people taking antidepressants has increased by more than 100% in the past decade. In 2016, the NHS doled out a record 64.7 million prescriptions – for context, there are 66 million people living in the UK. Could it be that the research being carried out today is paving the way for the use of psychobiotics – yoghurt included – as a mental health treatment? Yes, say those knee-deep in the science. ‘I think we are heading towards a scenario where in five years’ time everybody will be getting their microbiome measured in the same way that you get your cholesterol measured today,’ says Professor Cryan. ‘In this sense, I think we could really see a shift in preventative care, but also in treatment.’ A team in Canada is currently researching different strains of bacteria with the hope of being able to use microbiome analysis to predict risk, but also to create bespoke treatment for mental health conditions; Professor Cryan’s team is also in the early stages of developing a psychobiotic that could be used to treat the symptoms of mild depression.
But others are more cautious when I ask if this research can be translated into tangible treatment. ‘In order for psychobiotics to have a clinical application, we need more human studies,’ says Dr Philip Burnet, associate professor in the Department Of Psychiatry at the University of Oxford. ‘The problem we have is that in order to determine if they alone can treat someone who has depression, you would need to deny that person medication. You can’t do that, which makes it very difficult to test.’ Instead, Dr Burnet sees psychobiotics as supplements that can help medication to work better in people who don’t respond well to current treatment or for those who have low mood but no depression diagnosis. Adding another layer of complexity to psychobiotics is the care that has to be taken in discussing the potential of something other than tried and tested medication for mental health. The worry is that we risk adding to the stigma that (despite the best efforts of us all – this magazine included) continues to surround medically
‘IN FIVE YEARS, EVERYONE WILL BE GETTING THEIR MICROBIOME TESTED’
‘THIS COULD REVOLUTIONISE MANY AREAS OF MEDICINE’
treating your mind. ‘Medication has a really important role and people should never be afraid to take it if other lifestyle factors aren’t working,’ says Dr Rossi. ‘So I think mental health will always call for a holistic approach. But perhaps, ultimately, when someone goes to their GP and reports symptoms of anxiety or depression, doctors will prescribe both existing medication and psychobiotics.’ As to whether prebiotics or probiotics play the biggest role in influencing mental health, experts agree that we need more research on both. While they’re far from telling everyone to go out and stock up on probiotic supps, Lactobacillus and Bifidobacterium are among the most researched strains of bacteria, and the consensus is that supplements should contain upwards of five billion bacteria per capsule. But they do agree on the importance of eating a diet that’s rich in prebiotics. That includes plenty of legumes, Jerusalem artichokes, leeks, onions and asparagus. Professor Cryan sums it up: ‘We don’t have a strong enough evidence base yet to say that prebiotics have a positive effect on the brain in humans. But if you look at the Mediterranean diet, which is rich in prebiotics, it has been proven to be beneficial for brain health. The missing link thus far has been that this is down to your microbiome. We need to join the dots, but my gut instinct is telling me that, if you want to build up your stress resilience, a psychobiotic approach would be useful.’ So, what does all this mean for people like me? While the link between prebiotics and brain health might need more human studies to deliver concrete proof, upping my intake of prebiotic foods can only be a good thing. And it’s reassuring to know that dietary steps could future-proof my mental health should I reach the point of coming off my medication. As for where this research is headed, I’m excited – and I’m not the only one. ‘We are in the early days of unravelling the secrets of this system,’ says Dr Emeran Mayer, author of The Mind Gut Connection. ‘I think we currently know about 10%. But, in the next 10-20 years, this could revolutionise many areas of medicine.’ Now, there’s food for thought.