There are trillions of tiny bacteria living in our bodies.  These bacteria—particularly those in our gut, may improve digestion, boost immunity and, according to some preliminary studies, may even help us get leaner. Research is still emerging on just how important these mighty microbes might be for our health, but the early results are promising. There’s plenty you can do to encourage their growth. The most effective way is by drinking liquids packed with probiotics, the good bacteria that live in your gut and show up in fermented drinks.