It’s funny how we compulsively wash our hands, spray our countertops, or make a grimace when someone sneezes near us, when, in fact, each and every one of us is a walking petri dish! All the bacteria living inside you could fill a half-gallon jug — there are 10 times more bacterial cells in your body than human cells, according to Carolyn Bohach, a microbiologist at the University of Idaho. Don’t worry, though: most of these bacteria are helpful. In fact, we couldn’t survive without them.
For example, bacteria produce chemicals that help us harness energy and nutrients from our food. Germ-free rodents have to consume nearly a third more calories than normal rodents to maintain their body weight, and when the same animals were later given a dose of bacteria, their body fat levels spiked despite the fact that they didn’t eat any more than they had before. Gut bacteria is also very important for maintaining immunity. (image source).