I was born by caesarean section, and was not able to be breastfed. That makes me a perfect poster child for the intractability of the gastro-intestinal tract in the 21st century. If I had known more about the gut back then, I could have placed bets on what illnesses I would contract in later life. At first I was lactose intolerant. I never thought about why I was suddenly able to drink milk again at the age of five; at some point I got fat, then thin again. Then, for a long time, I was fine. Until I got ‘the sore’.

When I was seventeen, I developed a small sore on my right leg, for no apparent reason. It stubbornly refused to heal, and after a month I went to see my doctor. She didn’t really know what it was, and prescribed me some cream. Three weeks later, my entire leg was covered in sores. Soon they spread to my other leg, my arms, and my back. Sometimes they appeared on my face. Luckily, it was winter at the time, and everyone thought I had cold sores and a graze on my forehead.

No doctor was able to help me — giving me vague diagnoses of some kind of nervous eczema. They asked me about stress and psychological problems. Cortisone helped a little, but as soon as I stopped using it, the sores just came back. For a whole year, in summer and in winter, I wore tights to stop my sores from weeping though my trousers. Then I pulled myself together and started doing some research of my own. By chance, I came across a report about a very similar skin condition. A man had contracted it after taking antibiotics, and I, too, had had to take a course of antibiotics just a couple of weeks before my first sore appeared.

From that moment on, I ceased to treat my skin like that of a person with a dermatological problem, and began to see it as the skin of a person with an intestinal condition. I stopped eating dairy products, cut out gluten almost entirely, swallowed various bacteria cultures, and generally improved my diet. I also carried out some pretty crazy experiments on myself … if I had already been studying medicine at that time, I wouldn’t have dared do half of them. Once, I overdosed on zinc for several weeks, causing me to have an extremely heightened sense of smell for the next few months.

With a few tricks, I finally managed to get my condition under control. This success gave me a lift, and I experienced with my own body the reality that knowledge is power. That’s when I started studying medicine.

In my first semester as a student, I was at a party where I ended up sitting next to a guy who had the smelliest breath I have ever smelled. It wasn’t a typical bad-breath smell — not the scratchy hydrogen-breath odours of stressed-out middle-aged gentlemen, nor the sugary-foetid funk from the mouth of an elderly aunt with too sweet a tooth. After a while, I moved away and sat somewhere else. The next day, he was dead. He had killed himself. I couldn’t get him out of my mind. Could it have been a diseased gut creating that smell, and if so, could a diseased gut also have affected his psychological state?

A week later, I decided to share my suspicion with a good friend. And a few months after that, the same friend contracted a bad case of gastroenteritis, which left her feeling very poorly. The next time we met, she told me she thought there might be something in my theory, as her illness had made her feel worse than she ever had before, psychologically as well as physically. Her comments inspired me to start looking more closely at this subject matter. Soon, I discovered there was an entire branch of medical research investigating the links between the gut and the brain. It’s a rapidly growing field of study. Ten or so years ago, there were hardly any published studies on the subject, but now there are several hundred academic articles covering the field. The influence of the gut on our health and wellbeing is one of the new lines of research in modern medicine! The renowned American biochemist Rob Knight told the journal Nature that the field offered at least as much promise as stem-cell research. I had stumbled upon a subject I found more and more fascinating.

As I continued my medical degree, I realised how neglected, even looked down upon, this area is in the medical world. This is all the more surprising when you consider what an extraordinary organ the gut is. It accounts for two-thirds of our immune system, extracts energy from sandwiches and vegetarian sausages, and produces more than twenty unique hormones. Most doctors learn very little about this in their training. When I visited the ‘Microbiome and Host Health’ symposium in Lisbon in May 2013, the number of participants was modest. About half came from institutions with the financial wherewithal to allow them to be among the ‘pioneers’, including Harvard, Yale, Oxford, and EMCL Heidelberg. I’m sometimes shocked by the way scientists huddle behind closed doors to discuss their important research results, without informing the public about them at all. Academic caution is often preferable to premature publication. But fear can also destroy opportunities. It is now generally accepted in scientific circles that people with certain digestive problems often suffer from nervous disorders of the gut. Their gut then sends signals to the part of the brain that processes negative feelings, although they have done nothing bad. Such patients feel uneasy, but have no idea why. If their doctors simply treat them as irrational mental cases, it can be extremely counterproductive. And this is just one example of why some research results should be published more quickly.

And that is my aim in writing this book: I want to make new knowledge available to a broad audience, and communicate the information that scientists bury in their academic publications or discuss behind closed doors at scientific meetings, while many ordinary people out there are searching for answers. I know there are many patients suffering from unpleasant conditions who are frustrated by the medical world. I can’t offer any panaceas, and keeping your gut healthy is not a miracle cure for everything. But what I can do is to show, in an entertaining way, why the gut is so fascinating, what exciting new research is currently underway and how we can use this new knowledge to improve our daily lives.
My medical studies and my doctoral research at the Institute for Medical Microbiology have given me the skills to sift and sort scientific data. My own personal experience has helped me develop the ability to communicate this knowledge to people. My sister has given me the support I needed to keep me on the right track — listening to me read aloud from my manuscript and saying, with a charming grin, ‘I think you better try that bit again.’