Your body breaks it down and uses some of it for energy, so you basically breathe/pee some of it out, and some of it will be used to make proteins like enzymes and tissue. I think. I was really interested by this and being a biology student (and a geek) I read about it when I restarted SW lol. But student is the key word and unfortunately some of it didn't really make sense lol that's what I took from it