We talk of Old Wives Tales, but many of the health-related ones persist today - along with some new ones. The British Medical Journal has published an article from the Indiana University School of Medicine that examines seven myths that trouble some people today.

- "You should drink 8 glasses of water daily." There's no evidence to support this, whereas drinking excess amounts of water can be dangerous - water intoxication, hyponatremia, and even death. Just drink when you're thirsty.
- "We use only 10% of our brains." Einstein never said this. The postulated "non-functioning" 90% has never been located. Metabolic studies reveal no dormant areas.
- "Hair and nails continue growing after death." This myth may be based on known retraction of the skin around the hair and nails after death, due to drying or desiccation of the skin. But no growth occurs.
- "Shaving hair makes it grow back faster." In 1928 a clinical study showed that shaving had no such effect. This has been confirmed in subsequent studies, but the myth persists.
- "Reading a dim light ruins your eyesight." Poor lighting can make it seem difficult to focus; it also slows your blinking and your eyes may dry more. But these effects don't persist. Reading in a dim light is most unlikely to cause a permanent change on the function of structure of the eyes.
- "Eating turkey makes you drowsy." Tryptophan is found in turkey flesh, and tryptophan is involved in sleep and mood control, and can cause drowsiness. However, the amount of tryptophan in turkey is no more than that in chicken or minced beef, and pork or cheese contain even more. Don't forget that any large solid meal (like a Christmas or Thanksgiving dinner) diverts blood from the brain to the stomach, to aid in digestion, so that drowsiness ensues.
- "Mobile phones cause electromagnetic interference in hospitals." While such interference is remotely possible, actual cases are few and far between. At the mayo Clinic in 2005, in 510 tests involving 16 medical devices and 6 mobile phones, the incidence of a clinically important interference was 1.2%. On the other hand, mobile phone use by physicians in hospitals has been credited with reduced risk of medical error or injury resulting from delays in communication.

The authors of the article conclude that the persistence of simple medical myths point to the need to continue to question what other falsehoods physicians may endorse, and to encourage reliance on well-controlled evidentiary studies. If you want to find the references to the statements about individual myths, go to the article itself.