Longevity & AgingAging Gut Loses Its Defenses and Lets Harmful Bacteria Take Over
As the gut ages, its immune defenses weaken and its bacterial community shifts in dangerous ways. Researchers studying young and old mice found that aging intestines accumulate senescent cells, lose key immune signals like IgA, and see beneficial bacteria replaced by harmful species. The intestinal barrier also deteriorates, allowing bacterial byproducts to leak into the bloodstream. These changes reinforce each other in a vicious cycle: a weaker immune system allows bad bacteria to thrive, and those bacteria further damage gut defenses. When a dangerous pathogen was introduced, older mice showed far more inflammation than younger ones, suggesting the aged gut is both more vulnerable and less capable of mounting a targeted immune response.
