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.”
At medical school we were taught that gut bacteria help to protect your intestines from dangerous invaders; that they synthesise a few vitamins; and that they gobble up fibre that our bodies can’t digest, making smelly flatus (farts).
How to improve your gut…
Feed the good bacteria in your gut with the foods they like. These are known as “prebiotics”, and they act a bit like scattering fertiliser on your lawn. There are a range of foods that have been shown to be highly effective at encouraging the growth of “good” bacteria, and fortunately they are also extremely tasty. Try fermented foods — sauerkraut, kimchi and [the milk drink] kefir all contain very high levels of prebiotics. There are billions of them in a single gram of fermented food. My book [see end of article] is packed with recipes.
Cut down on sugar. Refined carbohydrates and processed foods are more likely to encourage the growth of bacteria that are bad for your health. Avoid unnecessary antibiotics, too.
Open the windows and get your hands dirty, preferably by gardening. This will connect you with the trillions of bacteria that live in the soil. It’s also the best way to ensure you get really fresh fruit and vegetables.
Do intermittent fasting. Studies have shown that this increases levels of a particularly beneficial group of bacteria called Akkermansia. Higher levels of these bacteria are linked to a lower risk of obesity and type 2 diabetes.
Reduce your stress. There is a close link between the mind and the gut and a whole new area of science, called psychobiotics, is exploring this.
Now we know the gut also...
Helps to regulate our body weight. The mix of microbes in your gut can affect how much energy your body extracts from the food you eat; they generate their own hunger signals; they may help decide which foods you crave; they also help to determine how much your blood sugar spikes in response to a meal. The good news is you can change your microbiome so it works with you, rather than against you.
Gut bacteria not only protect us from invaders, they also regulate our entire immune system. Over the past 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 got out of control. There is growing evidence that changing the mix of bacteria in your gut can reduce the impact of these diseases.
Gut bacteria also take the bits of food our body can’t digest and convert them into a wide range of hormones and chemicals. These, it seems, can affect our mood, as well as our appetite and general health. Scientists are now exploring how changing your biome may help reduce anxiety and lessen depression.
The tragedy is that over the past few decades we have been laying waste to our microbiome and its population of beneficial microbes. Just as we have ravaged the rainforests and consigned numerous animal species to oblivion, so we have decimated the populations that live inside us. Fortunately we can help them bounce back. Whether we’re fit or sick, happy or depressed, overweight or slim, we can all benefit from taking better care of our gut garden.
The Clever Guts Diet by Dr Michael Mosley is available from the RT Bookshop