I spent the holidays with my sister, a former scrub nurse, and was treated to a parade of what I call "new wives' tales": Drink more water. Don't use salt. Turn on more light to read or you'll go blind. In fact, as Rachel Vreeman and Aaron Carroll of Indianapolis' Reginstrief Institute write in the British Medical Journal, many of the "facts" that even medical professionals assume to be true have no backing in the literature. Take the one about reading in dim light. Our great-grandfathers relied on candles and lanterns, yet myopia has increased in the last century. Maybe it's all just to keep romance alive as we've become fatter and more sedentary.  Or take the one about the turkey. People fall asleep...