Debunking Top Health Myths Even Doctors Believe

(SPM Wire) Do you think that you need eight glasses of water a day, that reading in dim light damages your eyes or that eating turkey makes you sleepy? Think again.

In a study entitled "Medical Myths Even Doctors Believe" published in the "British Medical Journal," Indiana University School of Medicine researchers explored some commonly held and untrue medical beliefs.

The researchers studied various myths -- including those seemingly age-old beliefs that people only use 10 percent of their brains and that hair and fingernails continue to grow after we die.

The surprising findings are that all these beliefs were unproven or untrue.

"We got fired up about this because we knew that physicians accepted these beliefs and were passing this information along to their patients… We didn't set out to become myth busters," said the study's co-author Dr. Aaron Carroll, assistant professor of pediatrics and a Regenstrief Institute, Inc. affiliated scientist.

The first belief they explored was that people should drink at least eight glasses of water a day. This advice has long been promoted as healthful as well as a useful dieting or weight control strategy.

"When we examined this belief, we found that there is no medical evidence to suggest that you need that much water," said Dr. Rachel Vreeman, a pediatrics research fellow and co-author of the new study.

She thinks this myth can be traced back to a 1945 recommendation from the Nutrition Council. But an important part of the Council's recommendation has been lost over the years -- the large amount of fluid contained in food, especially fruits and vegetables, as well as in the coffee and soda people drink each day should be included in the recommended total.

Indeed, drinking excess water can be dangerous, resulting in water intoxication and even death, the study authors note.

Even before Abe Lincoln was told that reading in dim candle light was bad for his eyes, people have believed that reading in dim light causes permanent eye damage. And ever since, generation after generation of parents have thusly admonished children caught reading with flashlights under their blankets.

However, the new study found no evidence that reading in dim light causes permanent eye damage. It is true that eye strain can occur in dim light, causing some temporarily decreased acuity, but after rest the eyes return to their full potential.

And don't worry about falling asleep at the dinner table after gnawing on a turkey drumstick.

Yes, scientific evidence supports that tryptophan, which is contained in turkey, can cause drowsiness. However, turkey doesn't contain an exceptional amount of tryptophan. In fact, turkey, chicken, and ground beef contain about the same amount of tryptophan and protein sources like pork and Swiss cheese contain more tryptophan per gram than turkey.

So why do people believe eating turkey makes them sleepy but never feel that way after a burger or pork chop? This myth most likely gained credence because turkey is often consumed during large, heavy dinners. It's the total content of the meal that makes one feel lethargic.

Dr. Vreeman and Dr. Carroll also explored the popular belief that we use only 10 percent of our brains. MRI scans, PET scans and other imaging studies show no dormant areas of the brain, and even viewing individual neurons or cells reveals no inactive areas of the brain. Metabolic studies of how brain cells process chemicals show no nonfunctioning areas.

This myth probably originated with self improvement experts in the early 1900s who wanted to convince people that they had yet not reached their full potential. With the help of these self proclaimed experts one could tap into the 90 percent of the brain supposedly not being used.

The study also showed that finger nails and hair do not grow after death and that shaved hair does not grow back faster, coarser or darker, among other popularly-held incorrect medical myths.