Only in the last five years have we realised that we have this new organ – the microbiome – that weighs about the same as your brain (around 3lb) and contains 100 trillion microbes. We’re starting to understand how important these organisms are; while we once associated microbes with poor health, we now know most of those in the gut are beneficial.
We’ve made a range of discoveries about microbes, showing they’re key to our immune systems; play a role in allergies and autoimmune diseases; aid weight management; and produce hundreds of chemicals including serotonin, which is involved in mood, sleep and memory, and vitamins. They help us understand why some cancer treatments work in some people and not others. A recent study found that when we transplant poo from younger fish into older ones, they live longer – so microbes may have an anti-ageing role, too.
TIM SPECTOR is a professor of genetic epidemiology and director of the TwinsUK Registry at King’s College, London. He is chief strategy officer at Map My Gut (mapmygut.com) and author of The Diet Myth (W&N, £8.99)
In the early years of life, your gut bugs are dependent on various factors. If you were born by Caesarean and bottle-fed, we know you have a less diverse community of microbes. We know that people born this way are more likely to be overweight and have allergies, for example.