Here’s a little secret about medicine: It changes its mind. And thank goodness it does. Not because doctors were foolish 30 years ago. Not because researchers were incompetent. And certainly not because your grandmother was trying to lead you astray when she insisted that whatever she was recommending had “been proven.” We simply don’t know what we don’t know. Medical advice is generally based on the best evidence available at the time. Then larger studies are conducted. Peop