Aaron E. Carroll
Rachel C. Vreeman
Drink eight glasses of water a day. Don't read in dim light or you'll ruin your eyes. Eating turkey makes you tired. Shaving your hair makes it grow back coarser.
Tried and true medical advice, right? Wrong.
"Despite their popularity, all of these medical beliefs range from unproved to untrue," say Rachel C. Vreeman and Aaron E. Carroll, researchers in the Children's Health Services Research program at the IU School of Medicine. Carroll is also an affiliated scientist at the Regenstrief Institute for Health Care in Indianapolis.
Vreeman and Carroll have both reported widely on effective ways to improve children's health. Their study of medical myths--which drew the attention of The Today Show, among other media-- arose from discussions of how seldom physicians pause to examine beliefs they already hold as true. "Sometimes even doctors are duped, say Vreeman and Carroll. "While some of these myths simply do not have evidence to confirm them, others have been studied and proved wrong."
The researchers picked seven common medical or medicine-related beliefs held by physicians and the general public. They reviewed the beliefs, searching extensively for evidence. Here's some of what they found:
People should drink at least eight glasses of water a day. "Existing studies suggest that adequate fluid intake is usually met through typical daily consumption of juice, milk, and even caffeinated drinks," the co-authors conclude.
Shaving hair causes it to grow back faster, darker, or coarser. "Strong scientific evidence" disproves this claim, say Vreeman and Carroll. "As early as 1928, a clinical trial showed that shaving had no effect on hair growth.... Shaved hair lacks the finer taper seen at the ends of unshaven hair, giving an impression of coarseness. Similarly, the new hair has not yet been lightened by the sun or other chemical exposures, resulting in an appearance that seems darker than existing hair."
Reading in dim light ruins your eyesight. "The fearful idea that reading in dim light could ruin one's eyesight probably has its origins in the physiological experience of eye strain. ...The majority consensus in ophthalmology, as outlined in a collection of educational material for patients, is that reading in dim light does not damage your eyes.... Hundreds of online expert opinions conclude that reading in low light does not hurt your eyes."
For a complete account of the medical myths, see http://www.bmj.com/cgi/content/full/335/7633/1288. Vreeman and Carroll acknowledge the "light-hearted" nature of their debunking but conclude with a more serious purpose to their review: "Physicians would do well to understand the evidence supporting their medical decision making. They should at least recognise when their practice is based on tradition, anecdote, or art. While belief in the described myths is unlikely to cause harm, recommending medical treatment for which there is little evidence certainly can. Speaking from a position of authority, as physicians do, requires constant evaluation of the validity of our knowledge."
