Medical myths: Tiring turkey and more wives' tales

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What if someone told you turkey doesn't make you tired, or that you nails really don't keep growing after you die? The answer: The British medical journal BMJ. Last month, the journal published a list of health myths related to the holidays. Here are the myths: • People only use 10 percent of their brains This myth has been around for more than a century. Some believe it came from Albert Einstein, although the authors found no evidence of that. What they did find were studies that show people use much more than 10 percent of their brains. For example, when almost any area of the brain is damaged, it has "specific and lasting effects on mental, vegetative and behavioral capabilities." Also, imaging studies have found no area of the brain is completely inactive. • Hair and fingernails keep growing after death While it's impossible for the body to continue the complex hormone regulation needed to cause hair and nails to grow after death, this myth does have a basis in a biological phenomenon that sometimes occurs after death. When someone dies, dehydration of the body can cause the skin around the hair or nails to retract, creating the appearance of increased length. But the authors say this is an optical illusion. • Shaving causes your hair to grow back faster, darker or thicker Several studies show that shaving has no effect on the thickness or rate of new hair growth. But because shaved hair is blunt, and doesn't have the finer taper at the ends of unshaven hair, it can give an impression of being coarse. And new hair sometimes appears darker because it has not yet been lightened by the sun or other chemical exposures. • Reading in dim light ruins your eyesight While reading in dim light can cause eye strain, and the uncomfortable effects that go along with it such as dryness and difficulty focusing, it does not cause permanent damage, the authors say. • Eating turkey makes you especially tired If turkey contains tryptophan, and science has found that tryptophan can cause drowsiness, how is this medical belief a myth? The authors say turkey doesn't contain "an exceptional amount of tryptophan." In fact, turkey, chicken and minced beef contain nearly the same amounts of the amino acid. Other proteins, such as pork or cheese, contain more per gram than turkey. Perhaps the reason turkey has long been accused of making people extra sleepy is because of all the overeating we do on Thanksgiving. Studies show that eating any large, solid meal can make you tired because blood flow and oxygenation to the brain decreases. • Cell phones cause significant electromagnetic interference in hospitals Hospitals widely banned cell phone use after a front- page Wall Street Journal story cited an article detailing more than 100 reports of suspected electromagnetic interference with medical devices before 1993. But an Internet search by the study's authors could not find any cases of death caused by use of a cell phone in a hospital. They did find reports of less serious events, such as false alarms or incorrect medical readings. Meanwhile, subsequent studies show little or no interference. For example, a 2007 study examining mobile phones "used in a normal way" found no interference in 300 tests in 75 treatment rooms.