The following ideas are scientifically correct, right?
>People should drink at least eight glasses of water a day
>People use only 10 percent of their brains
>Eating turkey makes us sleepy
>Shaving hair causes it to grow back faster and coarser
>Reading in dim light ruins your eyesight
>Hair and fingernails continue to grow after we die
Wrong. These are some commonly held medical myths that have been around as long as some of us have lived and longer. At Indiana State University School of Medicine researchers decided to investigate some myths that most of us have grown up with.
“We got fired up about this because we knew that physicians accepted these beliefs and were passing this information along to their patients. And these beliefs are frequently cited in the popular media,” says co-author Aaron Carroll, MD, MS, assistant professor of pediatrics and a Regenstrief Institute, Inc. affiliated scientist.
Co-author Rachel Vreeman, MD, a pediatrics research fellow, says, “Whenever we talk about this work, doctors at first express disbelief that these things are not true. But after we carefully lay out medical evidence, they are very willing to accept that these beliefs are actually false.”
>People should drink at least eight
glasses of water a day
The first belief they explored, that people should drink at least eight glass of water a day has 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. Vreeman. The myth can be traced back to a 1945 recommendation from the Nutrition Council that a person should consume the equivalent of eight glasses (64 ounces) of fluid a day. 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 as part of the 64-ounce total. And conversely, the study authors noted that drinking excess water can be dangerous, resulting in water intoxication and even death.
>People use only 10 percent of their brains
This statement has been erroneously credited to Albert Einstein and is often cited by everyone from physicians to popular comedians. The study authors found that there are a lot of ways to disprove this belief. 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.
Carroll and Vreeman think 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. By paying these possible descendants of snake-oil salesmen, one was supposed learn how to be able to tap into the 90 percent not being used.
>Eating turkey makes us sleepy
Both Dr. Vreeman and Dr. Carroll admit that they believed that eating turkey makes one especially drowsy. Scientific evidence supports that tryptophan, which is contained in turkey, can cause drowsiness. But they found that turkey doesn’t contain an exceptional amount of tryptophan. In fact, turkey, chicken, and ground beef contain about the same amount of tryptophan. 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? Again, this is a belief that the media, and other pop culture icons frequently repeat, popularizing the myth in spite of the easily accessible data on percentage of tryptophan in various products. Most likely, according to the study authors, this myth gained credence because turkey is often consumed during large, heavy dinners. It’s the total content of the meal that makes one feel lethargic.
>Reading in dim light ruins your eyesight
Even before Abe Lincoln was told that reading in dim candlelight was bad for his eyes, people have believed that reading in dim light causes permanent eye damage. Generation after generation of parents have warned children (future physicians included) caught reading with flashlights under their blankets that reading in poor light ruins your vision. The study authors found no evidence that reading in dim light causes permanent eye damage. It is true, they say, that eyestrain can occur in dim light, causing some temporarily decreased acuity, but after the are rested the eyes return to their full potential.
>Shaving hair causes it to grow
back faster and coarser
The two researchers also explored a frequently held belief related to
hair—that shaved hair grows back faster, coarser and darker. They found
a 1928 randomized clinical trial, which compared hair growth in shaved
patches to growth in nonshaved patches. The hair that replaced the
shaved hair was no darker or thicker, and didn’t grow in faster. So why
has this myth persisted almost 80 years after it was disproved and in
the light of more recent studies which confirm the 1928 work? Again,
optical illusions may be partially responsible, according to the study
authors. When hair first comes in after being
shaved, it grows with a blunt edge on top. Over time, the blunt edge
gets worn so it may seem thicker than it actually is. Sun naturally
bleaches hair over time, so hair, which is just emerging after an
individual has shaved seems darker, but actually is no darker than any
new hair growth.
>Hair and fingernails continue
to grow after we die
Another hair-related myth is that fingernails and hair grow after death. Most physicians the study authors queried initially assumed this belief was true. But when they thought about it, they knew it couldn’t possibly be valid. This myth likely persists because of an optical illusion—and because it’s just so creepy.
A Lighthearted Way of Teaching Future Experts to Question Common "Knowledge"
Why have these myths been perpetuated? Dr. Carroll and Dr. Vreeman believe it’s because they are repeated to us by experts. “Until someone takes the time to question and look for evidence, medical myths will remain accepted beliefs. We have tried to show through science and research why certain widely accepted beliefs are untrue. To some extent this is what we do in our regular jobs every day, teaching medical students and residents (physicians in training) to question what they hear,” said Dr. Carroll. “This study was a lighthearted way to remind people that first they might believe things because they have heard them from other people, especially from experts; and second, staying current is not just a matter of adding new knowledge onto the things we already believe. Sometimes you really have to look back on things already in your head or things you already believe to be true and reinvestigate or investigate for the first time whether those things [really] are true,” said Dr. Vreeman.
Dr. Vreeman and Dr. Carroll, who are with Children’s Health Services Research in the IU School of Medicine’s Department of Pediatrics, are currently working on a book examining dozens of other popular medical beliefs to see if they are true, false or unproven. So was your mother correct when she said your chewing gum would stay in your stomach for seven years? Dr. Carroll and Dr. Vreeman, both pediatricians with Riley Hospital for Children, one of the nation’s leading centers of excellence in pediatric medicine, will let you know in 2008.
This research, entitled “Medical Myths Even Doctors Believe” was published in the Christmas issue of the British Medical Journal.
Adapted from materials provided by Indiana University.
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