While probiotic supplements add more good bacteria to the gut, it’s just as important to nourish the good bacteria you already have. Probiotics found within food are naturally created by the process of fermentation.

Prebiotics, meanwhile, are certain plant fibers that human cells are unable to digest. That’s not necessarily a bad thing, though—good bacteria in the gut break down these prebiotic fibers and use them for fuel, in turn promoting gut health.