Oct 10 2025 Everywhere you go, you carry a population of microbes in your gastrointestinal tract that outnumber the human cells making up your body. This microbiome has important connections to health in your gut, brain and immune system. Some resident bugs produce vitamins, antioxidants, nutrients and other helpful compounds. Even those whose direct effects seem neutral take up space that makes it harder for harmful microbes to move in. There is still much to be understood about the gut