Debunking Top Health Myths Even Doctors Believe

(SPM Wire)  Do you believe 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 but untrue medical beliefs. 

The researchers studied various myths -- including those 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 are untrue.

"We got fired up about this because we knew that physicians accepted these beliefs and were passing this information along to their patients," said the study's co-author Dr. Aaron Carroll.

The belief that people should drink at least eight glasses of water a day has long been promoted as healthful as well as a useful weight control strategy.

"When we examined this belief, we found there is no medical evidence to suggest that you need that much water." 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 – that the large amount of fluid contained in food, especially fruits and vegetables, as well as the coffee and soda people drink each day, should be included in the total. 

Even before Abe Lincoln was told that reading by candlelight was bad for his eyes, people have believed that reading in dim light causes permanent eye damage. However, the new study found no evidence of this. While it is true that eye strain can occur in dim light, 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, 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, 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? 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.

Regarding 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.

The study also showed that fingernails 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.