New research suggests some of our thoughts and emotions are controlled by our digestive systems, not our minds. Stylist investigates the rise of the gut brain

Words: Charlotte Haigh MacNeil

When did you last describe a situation as “gut-wrenching”, or admit to feeling “gutted”? Whether we’re disappointed, angry or nervous, every day we subconsciously listen to warnings from our bellies – our “gut instincts” as we know them – from that fluttering feeling before a date to a lurching stomach after opening a bank statement. But what if those signals were more than just side effects of how we’re feeling? What if they were actually the cause, and by controlling them, you could improve everything from your happiness to your stress levels?

That’s the incredible new theory emerging from various pioneering studies. In fact, our gut is thought to influence our personalities and behaviour so much that it’s now being dubbed our second brain. A team of researchers led by Professor John F Cryan at University College Cork has found that we’re more likely a probiotic containing a strain of healthy gut bacteria for four weeks and, remarkably, scientists now believe around 95% of the body’s serotonin (the happy hormone) is produced in our guts.

Plus, new research by the Weizmann Institute of Science in Tel Aviv says that our gut bacteria could influence how we break down sugar – and therefore make us healthier, or attain a healthy weight more easily. It’s even thought that microbes in our stomachs could influence our anxiety levels, make us more content, and ease symptoms of IBS. And the momentum shows no signs of slowing; there are a slew of healthy gut cookbooks out in the coming months, following last year’s international bestseller Gut, by 25-year-old Giulia Enders, and Brain Maker by Dr David Perlmutter. Forget mind over matter. It seems the true power for change lies with your gut.

“The gut contains more neurons [which receive and send signals within the body] than your spinal cord,” explains Cryan. In fact, over 100 million neurons – more than in a cat’s brain – line the digestive tract and respond to emotions, receive impulses and log experiences, just like your brain. But that’s not all. Science now believes some of the gut’s microbiota (a community of microorganisms which live in the digestive tract and perform a number of functions, such as helping digest food and acting as a barrier for the immune system) play a critical role in the brain’s emotional behaviour. How? They release neurotransmitters, which send messages from neuron to neuron, communicating with the brain via the vagus nerve – a cranial nerve supplying the heart, lungs and digestive system.

While the idea that your insides are teeming with bugs isn’t exactly pleasant, it’s already well known that they play a crucial part in keeping you healthy. Though some bacteria (pathogenic) can cause disease, many are beneficial. “These gut microbes used to be seen mainly as helping to digest food,” says Erica Sonnenburg, microbiologist at Stanford University, and leading researcher into the link between diet and gut microbes. “What we’re understanding now is that they’re wired to the rest of the body and have other roles too.” We all have varying levels of different bacteria, determined by lifestyle and environment right from the beginning of life; for example, someone who was born naturally has different microbiota to someone who was born via caesarean, as a baby’s gut is sterile inside the womb and the baby picks up bacteria from the mother as it passes through the birth canal. Yet the good news is that we can control them – and thus boost our wellbeing – through simply altering what we eat.

Our response to stress, our ability to learn and our character traits could be a result of the state of our microbiota early in life,” says Sonnenburg. “It’s possible that if you have an anxiety disorder or depression, that could be partly down to the microbes in your gut.” But, she cautions, the research is in its early days and while scientists have already made a connection between autism and an imbalance in gut bacteria, we don’t have many concrete answers yet. “There are trillions of bacteria in the gut and the brain is a very complex organ,” she says. “It will take a while to figure out exactly how the two interact and how our microbiota might influence our feelings and behaviour.”

Potentially, though, adjusting our microbiota could be a next-generation solution to mental health conditions such as depression, OCD and anxiety. There are already some clues to show that introducing useful microbes into the gut might have an impact on our minds, especially when it comes to stress. In 2011, a study found volunteers who took two bacteria – lactobacillus helveticus and bifidobacterium longum – for 30 days experienced less depression and anxiety. A more recent study, at UCLA, found women who ate two bacteria-containing yoghurts every day for a month showed reduced activity in the part of the brain that processes emotion.

Getting the right mix of bacteria in the gut could also help reduce long-term health risks for those suffering with chronic stress. As the body can’t differentiate between physical and emotional stress, each time our anxiety levels rise, it reacts in the same way, via the adrenal glands which produce the stress hormone cortisol. Too much cortisol and adrenaline can lead to depressive disorders, high blood pressure – and, potentially, autoimmune disorders such as ulcerative colitis and multiple sclerosis. However some organisms in the gut – like bifidobacterium and lactobacillus, found in probiotic yoghurts – can help to turn off the reactionary fight or flight response and protect the body from the long-term damage of too much adrenaline.

So does this mean bacteria could be the new Prozac? “Treatments based on bacteria – which we call psychobiotics – may be very beneficial if you suffer from depression or anxiety,” says Cryan, who is researching the link between the gut and the brain. “We need more research but I’m hopeful they’ll be available in about two years.” Right now there haven’t been enough studies on humans for scientists to recommend a specific bacteria to beat low mood.

While the findings represent a leap in our understanding of how integral our stomachs are to our overall health, it’s still not clear whether stress alters our microbiota, or whether a particular microbiota can cause stress. “It’s a chicken-and-egg situation,” says Cryan. “For example, we know that many people with IBS, which is a disorder of the gut-brain axis [biochemical signalling between the gastrointestinal tract and the nervous system], have had some kind of significant stress before the age of 10, such as the death of a close family member or moving school and being bullied. That can upset the balance of their microbiota, as well as other factors including the immune system and the pain processing system, all of which are involved in IBS. But we also know that lowered levels of microbes can make stress more likely – which may further aggravate IBS. It becomes a vicious cycle.”

But while scientists are still looking for more solid evidence of the links between microbes and mood, a thriving microbiota has been proven to have a host of other benefits for your wellbeing. A tribe of diverse bacteria has been credited with maintaining a healthy weight, according to French researchers. It’s thought that unhealthy gut bacteria fuels cravings for the wrong types of foods, and by encouraging good bacteria to thrive in our microbiomes, we can lessen the cravings and live a healthier lifestyle. Good gut bacteria can also support your digestion and boost your immune system, protecting you against colds, flu and other infections.

But the chances are your microbiota isn’t in great shape. Living in an industrialised society, as opposed to a more traditional, rural way of life, has changed the amount and types of bacteria we routinely carry in our systems. “Studies have looked at the microbiota of people living a more traditional lifestyle, and it’s very different to ours,” says Sonnenburg. “They have about 1,600 bacterial species in their guts, compared to our 1,200.”

Our over-reliance on antibiotics also plays a part; “Antibiotics and our over-sterilised environment add to the problem,” explains Sonnenburg. “We’re always using antibacterial products, reducing our exposure to bacteria. We all need antibiotics sometimes but they destroy your microbes, so don’t take them unless you really have to. And if you do, take steps to bring back your community of microbes – increase your intake of yoghurt and fruit.

“Plus, our more refined diet lacks the fibre – found in roughage like cereal, fruit and vegetables – gut microbes feed on. We have about 10 times less fibre than more traditional communities. Even our stressful lives could contribute by making our guts sluggish, which might change the balance of microbes.”

Luckily, although your microbiota sets up home early in your life, there are steps you can take as an adult to boost it. First up are probiotics, which are good bugs in supplement form, usually capsules – try Solgar Probi 30 Billion Vegetable Capsules, £39.99 – but also in powders or yoghurt drinks [Bimuno powder, £8.99]. “We don’t know how many of the bacteria in these products actually get to the gut, because most are destroyed by stomach acid,” concedes nutritionist Ian Marber. “But even if only a handful make it, that’s helpful, because once in the gut they multiply. Look for a product with a few billion viable bacteria. The more bacteria, the more likely some will make it to the gut.”

As well as traditional supplements, increasingly innovative ways to help maintain good bacteria are emerging. IBS sufferer Andrew Marten launched Ohso in 2011, a chocolate bar containing over a billion live cultures that, it claims, is three times more effective at delivering live bacteria to your gut than dairy products. And perhaps it’s no coincidence that fermented food is one of the hottest trends right now as our knowledge and curiosity about our gut hits its peak. Not only is Korean kimchi (fermented raw vegetables) delicious, it’s good for us too – containing both probiotics and prebiotics, it feeds the live cultures in the foods, as well as helping the good bugs already in the gut to flourish. “As we gain more understanding of the importance of our microbiota so the popularity of fermented foods grows, such as sauerkraut, kefir (fermented milk) and kombucha (fermented tea), all of which promote the growth of healthy gut bacteria,” says food futurologist Dr Morgaine Gaye. London restaurant Aqua Kyoto features a menu crammed with fermented Japanese food, from seaweed to mango, while at the hottest bars you can now swig fermented cocktails – try the Contemplate Kombucha (gin, basil, agave, lemon and kombucha) at Jarr Bar in London’s Hackney Wick.

But you don’t need a whole new menu to feed your gut. “Complex carbohydrates, found in fruit, vegetables and legumes are high in fibre, which feeds good bacteria,” says Sonnenburg. “And we know people who eat a fibre-rich diet tend to live longer. A diet with plenty of fresh produce, grains, olive oil, some nuts, seeds and fish, is best for your microbiota.”

One final key is tackling stress. While the impact of relaxation on your microbiota isn’t fully understood, it can have other positive effects on the gut. Professor Peter Whorwell has pioneered gut-focused hypnotherapy, which uses visualisations – such as seeing your gut as a slow, smooth river – to ease IBS. “Hypnotherapy is very relaxing,” he explains. “It helps with stress-related IBS, but the visualisations also help you control the function of your gut.” A study he recently conducted found that 67% of people with IBS reported reduced pain after hypnosis, while depression and anxiety were halved.

Our knowledge of our second brain – and the bacteria making it function – is expanding all the time. So until we know more, one thing is for sure. Never underestimate the power of your gut instinct – it could be telling you more than you think.

How to harness the power of your gut: a guide to maintaining a healthy, happy stomach