How to revitalise your gut for a stronger immune system

Wouldn’t it be convenient if there were one thing behind the rise of so many of the health issues plaguing us in the 21st century, such as obesity, type 2 diabetes, allergies and intolerances, irritable bowels, depressed and anxious minds. All these things are being linked by emerging science to the microbes in our gut, that community of 30-40 trillion microscopic creatures that interact with our body systems in complex and still largely mysterious ways. Since the middle of last century, we’ve been slaughtering them with antibiotics and starving them with our diets, and now we’re paying the price. Or so the argument goes. This is a fast-evolving area of science and much is still not known.

That’s never stopped British doctor-turned-broadcaster Michael Mosley from using his influence to convince the masses to alter their lifestyle in response to the latest research. There have been books, TV shows and websites preaching the benefits of intermittent fasting (he developed the 5:2 diet) and the effectiveness of very-low-calorie regimes at reversing diabetes. Now, Mosley has the microbiome in his sights with a new book, The Clever Guts Diet, and its accompanying The Clever Guts Diet Recipe Book.

Microbial restoration is one of medicine’s new frontiers. Already we’re treating severe intestinal infections using faecal transplants from healthy donors. At Auckland’s Liggins Institute, there’s a groundbreaking study under way, dubbed the Gut Bugs Trial, in which bacteria from healthy, lean young people are being given in capsule form to teenagers who are clinically obese (this kind of thing has led to dramatic weight loss in mice). As ever, Mosley’s is more of an everyday, do-try-this-at-home approach. He’s among those who believe it’s possible to help the microbiome to bounce back with a diet based around foods that are good for it. Until relatively recently, it was impossible to study the thousands of different species living in our gut because most don’t survive when removed from our intestines.

But in the wake of the Human Genome Project, scientists are now able to sequence the DNA of the microbes expelled in our stools. It’s still tricky, however, for most of us to find out exactly what’s going on -and potentially wrong - in there. Online you’ll find several companies offering to sequence your microbiome. Mosley sent a poo sample to one called uBiome and was gratified to learn he has a lower-than-average population of Firmicutes, which have been linked with obesity, and lots of Bacteroidetes and Akkermansia, which are associated with leaner body types and less inflammation in the gut. “But it’s not at all clear how reliable this is.” he concedes.

“If I sent off my poo sample to five different centres, I don’t know whether I’d get five different results. I suspect there’s a lot of variability.” This lack of clear-cut diagnostic testing is one of the reasons sufferers of disorders such as irritable bowel syndrome and leaky gut have had to put up with a fair amount of eye rolling from their doctors. “We’re all quite simple as doctors,” says Mosley’s wife, Clare Bailey, who as well creating The Clever Guts Diet Recipe Book is also a practising GP. “We like to measure, define and test things, otherwise we feel a little bit awash. And this is an area where the science isn’t that clear yet. You can make a guess at how wrecked people’s microbiomes are by asking about their diet, how they’re feeling and what their symptoms are, but it’s not something that’s routinely picked up.”

Even the autoimmune disorder coeliac disease, characterised by a severe reaction to gluten, is under-diagnosed partly because the test commonly used to pick it up involves detecting antibodies produced in response to gluten, and most sufferers have been experiencing such unpleasant symptoms they’ve stopped eating foods containing it long before they turn up to be tested.

Obesity is another area in which doctors are struggling. Bailey says she’s spent advising her patients to eat less and do more exercise, but in most cases it’s been futile. Thanks to research by microbiologists, we now have a possible reason. It turns out that overweight people have a higher proportion of Firmicutes, a group of bacteria that are good at extracting extra calories from the food they consume. When the gut microbes of obese mice are transferred into specially raised germ-free mice, they get fatter - hence the Gut Bugs Trial at the Liggins Institute, which aims to do the opposite.

What we know for sure is that the community of bacteria in the gut is in a constant state of flux, as our microbes compete for space and resources. “It’s a pretty ferocious war, says Mosley. “You have survival of the fittest going on down there, although you may not be aware of it. They’re all fighting for dominance. So, yes, it’s war and we need to parachute in reinforcements every so often. Unfortunately, the modern lifestyle has unbalanced this battle. Broad spectrum antibiotics, which wipe out friendly bacteria along with life threatening infections, are only partly responsible. The typical Western diet also needs to be held accountable, which means another black mark against highly processed foods. “Emulsifiers, which are a form of detergent, are added to them for texture and to extend shelf life, " says Mosley.

“Feeding common emulsifiers to mice tilts their biome in an unhealthy direction and encourages the growth of bacteria that attack the mucous lining of the gut.” The equilibrium of microbes also appears to be affected by a diet high in sugar and fat. One Italian study comparing the gut microbiota of children in Florence with those living in a rural village in Africa’s Burkina Faso (where they exist mostly on a savoury porridge of millet and sorghum, vegetables and the odd chicken), found the Italian kids mainly had microbes belonging to the Firmicute group, whereas the Burkinabés’ were dominated by Bacteroidetes. There are plenty of other factors. In the West, drinking-water supplies are often chlorinated and fluoridated. Cheeses are pasteurised. Our lives are increasingly sterilised and sedentary. “We don’t go out as much, we live in more atmospherically controlled circumstances, our kids don’t run around in the dirt like they used to,” says Mosley.