The gut is not a glamorous organ. When I was at medical school many of my fellow students wanted to study the brain or do cardiology, saving lives by studying the heart. None of my friends wanted to dedicate their life to studying the gut.


And yet our gut is central to our mental and physical health. It’s also surprisingly clever. Did you know that there is a second brain down there, known as the enteric system, that contains the same sort of neurons and neurotransmitters as you’d find in the brain in your head? In fact, there are as many brain cells lining your gut as there are in the skull of a cat.

Even more impressively, there is a huge alien eco-system living down in your gut: trillions of different microbes, collectively known as the microbiome. Until recently we knew very little about the 1–2kg of microbes that live in the intestine, but in recent times there has been an absolute explosion of new and exciting gut-related research that has revealed the huge impact they have on our lives.


Hippocrates, the father of modern medicine, wasn’t overstating it when he wrote, “All disease starts in the gut.”