The Clever Gut Diet Introduction
Although this book has “diet” in its title, it is not really about losing weight. That may well happen, if you eat the foods and do the things I recommend, but that’s not its primary purpose. The Clever Gut Diet is a “diet” in the same way you might talk about being on a vegetarian diet or a Mediterranean diet. It’s not about calories or restriction; it’s about the sort of food and lifestyle changes you should make if you have gut problems, or simply want to keep yours in good condition.

The gut is not a glamorous organ. When I was at medical school many of my fellow students wanted to study the brain, as neurosurgeons, or become cardiologists, experts in the heart. I never heard anyone say they wanted to dedicate their life to the gut. And yet it is extraordinary—a part of the body, hitherto relatively unexplored, with which I have recently become rather obsessed. Thanks to a huge amount of new research, probing the world within our guts is changing our understanding of the way our bodies work.

As well as extracting energy from our food, the gut accounts for most of our immune system and produces more than two dozen hormones that influence everything from our appetite to our mood.

I also love the fact that, buried in our intestines, deep inside its tissue, is a very thin layer of brain. It’s called the enteric system and it is made up of the same cells, neurons, which are found in the brain. There are over one hundred million neurons in the gut, as many as you would find in the brain of a cat. Except, instead of being in one big lump, like the brain on top of your neck, the neurons in your gut are spread out in a thin mesh that extends all the way from your throat to your rectum. This “second brain” doesn’t do much geometry or worry about tax returns, but it does orchestrate digestion and moderate gut pain.

When we talk about having “gut feelings” or “gut instincts” we are reflecting the reality of how closely our guts and brains are entwined. In this book I am going to be talking a lot about the “gut-brain axis” and the new science that surrounds it.

Your gut is a wonderful piece of engineering and I hope, after you have read this, you will share my enthusiasm for it. But in many ways the star of the digestive show is not actually part of the human body at all—it is the 2 to 4 pounds of microbes that live in your gut and make up the microbiome.

Until recently the world of the microbiome was a dark, dank, and private one. Down there live creatures that have never seen the light of day, more than fifty trillion of them, at least one thousand different species, a richer diversity of life than you would find in a rain forest.

As is often the case with new scientific discoveries, a lot of genuine research has been misinterpreted and findings have been exaggerated. And, just as these microbes were previously ignored, now they are in danger of being seriously overhyped. Recent research shows that we are not “90 percent bacteria” and “10 percent human,” as many books and articles have claimed, but more like 50:50.1

In fact, according to one of the researchers who helped explode this myth, the proportions are so similar that “each defecation may flip the ratio to favor human cells over bacteria.”

More important, while there are foods that will help your microbiome thrive (and that’s why this book contains recipes), few of the products that are sold on this basis have credible science behind them. When it comes to prebiotics, probiotics, and supplements, I will show you what works and what doesn’t.

Our widespread ignorance about the microbiome arises from the fact that, until quite recently, its inhabitants, microbes, were impossible to study. We knew they helped protect the gut from dangerous invaders, that they synthesized a few vitamins, and that they gobbled up fiber that our bodies couldn’t digest.

Now we know they do far more than that:

1. They help regulate our body weight. As we’ll see in later chapters, the microbes in your gut can decide how much energy your body extracts from the food you eat; they control hunger signals, they help decide which foods you crave, and they determine how much your blood sugar spikes in response to a meal. Can your microbiome make you fat? It certainly can. Can you change your microbiome so it works with you rather than against you? You certainly can, and I will show you how.

2. The microbiome not only protects our guts from invaders, it teaches and regulates our entire immune system. Over the last half century we have seen a massive rise in allergic diseases, such as asthma and eczema, caused by an overactive immune system. We have also seen a huge surge in autoimmune diseases, ranging from inflammatory bowel disease to type 1 diabetes, which again are primarily caused by an immune system that has gotten out of control. I will show you how changing the mix of bacteria in your gut can reduce the impact of these diseases.

3. The microbiome takes the bits of food our body can’t digest and converts them into a wide range of hormones and chemicals. These, it seems, can control our mood, as well as our appetite and general health. Changing your biome may reduce anxiety and lessen depression.

The tragedy is that, in our ignorance, we have been laying waste to our microbiome and its population of microbes, or “Old Friends.” They’ve been given that name because they have evolved with us over millions of years, and also because so many of them are essential to our health. Just as we have ravaged the rain forests and consigned numerous animal species to oblivion, so we have decimated the populations that live inside us. Fortunately we can help these Old Friends bounce back. I will show you how.

I will also be looking into the latest treatments for a number of gut problems, ranging from gluten intolerance to irritable bowel syndrome. These are diseases that many people struggle with, in part because doctors are often bad at both diagnosing and treating them. They are frequently dismissed as “psychosomatic”—that is, the product of anxiety or depression.

The same used to be said of stomach ulcers. Also known as gastric ulcers, these are open sores that develop on the lining of the stomach and small intestine.

Back in 1994, when I made a television program about ulcers (which I unimaginatively called Ulcer Wars), they were common and considered incurable. It was widely believed that they were caused by stress, which made your stomach produce too much acid, and that was what did the damage. The standard medical advice was to eat bland food, change your stressful lifestyle, and take a drug to reduce acid production. If that didn’t work, and it often didn’t, you might find yourself in the hands of surgeons having parts of your stomach and small bowel removed.

But in Perth, Western Australia, there were a couple of doctors who did not think that stress was the real cause of ulcers. They argued that most ulcers were the result of infection by a previously unknown bacterium that they had identified and named Helicobacter pylori.

To make his point, in 1984 one of the scientists, Dr. Barry Marshall, brewed up a flask of Helicobacter and swallowed it. A few days later, as he smilingly told me, he started vomiting. He had himself endoscoped; a small tube was passed down his throat and into his stomach. Samples of his now inflamed stomach lining were removed. These showed that his stomach had been colonized by Helicobacter.

Barry’s wife, Adrienne, who worried that he would become seriously ill, insisted that he stop the experiment. So Barry took a handful of antibiotics, which he had previously shown could kill Helicobacter, and soon his stomach was back to normal.

Ten years later, and despite extensive research showing that a short course of antibiotics could cure stomach ulcers, most of the experts I interviewed for my film dismissed Barry’s work out of hand. One told me he refused to believe a major breakthrough could have come out of an “academic backwater like Perth.” A gut expert who reviewed my film in the British Medical Journal described it as “one-sided and tendentious.”

Normally you make a documentary, it goes out, and that is that. Not with Ulcer Wars. I received tens of thousands of letters (these were the days before the internet or email) from people in terrible pain, who had not responded to standard treatments. I ended up sending out thousands of fact sheets, describing the science and Barry’s antibiotics protocol.

I still have some of the letters I got back, including one from a guy called Brian whose ulcer was not responding to standard treatment and who had been told to give up the high-powered job he loved and have most of his stomach removed. He took my fact sheet to his doctor, and begged for a course of antibiotics. His doctor reluctantly agreed and within a couple of weeks he was completely cured. He wrote to me regularly afterward to say he was still going strong.

The tide slowly turned and I was delighted when Barry Marshall and Robin Warren won the Nobel Prize for Medicine for their work in 2005. Looking for and treating Helicobacter infection when people have gastric ulcers is now completely standard practice.

The point I’m making is not that antibiotics are the solution to everything. They aren’t and their overuse has created other serious gut problems. Nor am I suggesting that stress doesn’t matter. It does, and I will show you proven ways to de-stress.

The point is that many diseases have been dismissed as psychosomatic simply because doctors haven’t had the right tools to investigate them properly. In the 1930s asthma was treated by psychotherapy because of the mistaken belief that it was “all in the mind.” Autism and schizophrenia were once blamed on poor parenting.

One reason I’ve written this book is that I’m convinced that many common gut conditions are better treated by a change in diet than by drugs or antidepressants.

The initial chapters provide an overview of the gut, which I have written in the form of a journey through my own intestines. These chapters include not only what the gut does, but also what happens when it goes wrong.

Chapter 3 introduces us to the wonderful world of the microbiome and some of the more influential tribes that you will find down there.

Subsequent chapters look at the unexpected ways in which our microbiome influences us, before moving on to scientifically tested ways to keep it in good shape. And finally there is a section of recipes from nutritional therapist Tanya Borowski and general practitioner Clare Bailey.

I’ve learned a great deal that has surprised me, and gotten a lot of practical benefit from researching this book. I now eat a much wider range of foods, including fermented foods I’d never tried before. I’ve thoroughly enjoyed the journey. I hope you do, too.