How harmful are new wives' tales?

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 in front of the football after a big turkey dinner. True. They would also fall asleep in front of the football after a big tofurkey dinner. Thanksgiving football is seldom very compelling.

Most health myths are fairly harmless, and the fact is there is a lot about the subject we still don't know. President Eisenhower's doctors treated his heart problems with margarine. Our knowledge on saturated fats came later.

Maybe all my sister meant with her nagging about water and salt added up to this. She likes me. So take the New Year's health nagging in good spirit. After all, bad moods can be deadly.