In 45 years of writing about medicine and health, I’ve heard more than my share of myths and misinformation, from the merely nonsensical to the downright dangerous. And until I explored the evidence, I too occasionally fell for a “fact” that turned out to be less than met the eye.

Lately a number of medical writers have taken on these commonplaces and old wives’ tales.

Last year, Anahad O’Connor, who does so every week in his “Really?” column for Science Times, published “Never Shower in a Thunderstorm: Surprising Facts and Misleading Myths About Our Health and the World We Live In” (Times Books).

Now, Dr. Nancy L. Snyderman, a surgical oncologist at the University of Pennsylvania and a medical correspondent for NBC News, has a new book, “Medical Myths That Can Kill You  And the 101 Truths That Will Save, Extend, and Improve Your Life” (Crown).

The following myths owe something to both authors, and also to my own research. How well informed are you?