In the past few years, scientists have begun to uncover the multitude of ways in which the community of bacteria living in the our intestines, known as the microbiome, can impact our health. Not only do these (benign) bacteria help with metabolism and digestion, shifts in it are linked to a wide range of conditions including cancer, and diabetes, and perhaps even depression. In a recent study, researchers tracked how gut bacteria change with age – and then found a way to essentially turn back the clock, returning the microbiome to a more youthful state and extending lifespan.

The researchers found that as the subjects – flies in this case – aged, they have more and more bacteria in their guts, due to the suppression of molecules known as PGRP-SCs, which keep bacterial populations in check. All those germs put the lining of the gut on immune high alert, leading to inflammation and chronic inflammation, scientists increasingly think, can cause and exacerbate a wide range of diseases. When the researchers gave older flies PGRP-SCs, the number of bacteria in their gut decreased, and their microbiomes began to look much like those of younger flies. Not only that, they lived significantly longer than flies whose microbiome changes when untreated.

"This demonstrates that if we find ways of modulating our [bacterial] population that we will have the potential to influence longevity – in this case in flies, but potentially in humans as well," says Heinrich Jasper, a biologist at the Buck Institute for Research on Aging who led the study. "If we find ways of preventing similar changes in aging humans, we should be able to at least delay some age-related diseases and potentially extend our lifespan."

The way to do that, he says, will likely be some combination of medication and probiotics. Finding a gene that targets the equivalent of PGRP-SCs–those molecules that keep gut bacteria in check in humans–will help us keep our microbiome young even as we get older and allow us to stay healthier (and perhaps stick around) longer. And if a medication like that is making the gut a more supportive place for a healthful microbiome, the "good" bacteria we take in through probiotics – whether in fermented foods or via supplements – will help keep that ecosystem strong. "It's quite possible we'd have to attack this problem from both sides," he says.