HealthA new understanding of our relationship with our "friendly" gut microbes shows they actually have a dark side and help cause ageing. Here's how to fight back 4 February 2025 Yehrin TongAs human beings, we are all keepers of a vast menagerie. Every surface of our bodies, inside and out, is teeming with microorganisms. We have microbiomes on our skin, in our mouths and other orifices and especially in our intestines.In recent years, we have grown accustomed to thinking of these internal residents as benign, even essential to our health. Our guts are said to be full of friendly bacteria and other microorganisms that do us favours in return for us giving them a cosy home. That is true to some extent, but new research on the role of the gut microbiome in ageing is pointing to what would constitute a profound rethink of this relationship.In this emerging view, our gut microbes arent our friends, but an enemy at the gates. Far from being mutually beneficial, our relationship with them is more like a war of attrition a war we eventually lose. However, there are ways to postpone the inevitable.The gut microbiome is a community of perhaps 100 trillion microorganisms bacteria, archaea, fungi and viruses that dwell inside our intestinal tract, most abundantly in the colon. It is established early and stays with us throughout our lives, though it is in constant flux. Its a very complex, very dynamic community that depends on what we eat, who we interact with, says Dario Valenzano at the Leibniz Institute on Aging Fritz Lipmann Institute (FLI) in Jena, Germany.The ageing microbiomeIt also changes as we age. For most of our lives, the composition