"Don't swallow your gum, it'll take seven years for your stomach to digest!" "Ah, just pick it up off the floor — five second rule!" Most of us grew up with wives' tales like these, and probably believed them. But, as we've gotten older and wiser, we've found that many of them just aren't true — and that there are many health concerns that we really should be getting checked out instead. Here's a list of 30 medical myths, both old and new, that have been debunked.