'Gut health' is the wellness industry's buzzword of choice right now, with UK sales of digestive remedies set to reach £333 million by 2021. There's been some pretty groundbreaking research of late into a part of the body that, until relatively recently, has been taken for granted. So what does science actually now know about how the gut works, and does the secret to a healthy gut really lie in overpriced yoghurt drinks and chia seeds? Microbiologist Dr. Lindsay Hall is a research leader at the Institute of Food Research, and she really knows her bacteria. "The gut provides a home to trillions and trillions of beneficial microbes," she explains. "This complex ecosystem is called the microbiota, and the number of bacteria we have in our gut day-to-day is equivalent of about 2-3kg. We've known about these bacteria for years, but it's only really in the last 15-20 years – and, in a really focused way, in the last five years – that we've begun to understand the different health benefits that these bacteria actually provide us with." If you're anything like me, your knowledge of this complex microbial ecosystem probably begins and ends with the words 'good bacteria' and 'bad bacteria'. Years of yoghurt adverts where women complain about bloating before eating a magic fromage frais and having a giggle about nothing in particular have taught us that not all bacteria are bad. But in fact, the impact they have on our body – and potentially, our brain – is incredible. "The health benefits are fairly far-reaching. Obviously all this research is still ongoing, but it's all really, really exciting," Lindsay says. "Gut microbes are important in terms of modulating our gut function – so, transit time after a meal, keeping you regular, and maintaining a healthy barrier between what's in the gut and what's in the body. They're also super important for regulating your immune system, so they programme your white blood cells and tell them what to do, and they actually help us digest our food and extract energy and other key nutrients from it," she explains. So far, all pretty essential – but the theory currently at the forefront of research, Lindsay adds, is that gut bacteria can even control your brain function . Yeah, that stuff Martine McCutcheon was on about might just be that important. And the scientific developments don't end there. "Microbes basically impact on everything, in terms of the stuff we take for granted on a day-to-day basis to keep us healthy. The problem is, because these bugs are so important, if we come in and potentially disturb them – which we can do a number of different ways – that may mean it leads to disease," Lindsay says. "At this point in time, the research suggests that the microbiota is important in certain diseases. Allergies like eczema and asthma , or chronic inflammatory diseases like ulcerative colitis, potentially type 2 diabetes, are some of the diseases currently being tested in pre-clinical models."