Medical Myths Even Doctors Believe

Indiana University School of Medicine researchers explored seven commonly held medical beliefs. selected seven medical beliefs, espoused by both physicians and members of the general public, for critical review. They then searched for evidence to support or refute each of these claims.

The researchers explored various myths including:

* People only use 10 percent of their brains

* Hair and fingernails continue to grow after we die

* Eating turkey makes you sleepy

* People should drink at least eight glasses of water a day

* Shaving hair cause it to grow back faster or coarser

* Reading in dim light ruins your eyesight

These beliefs are commonly accepted, not only by the general population, but also by many physicians. The authors' surprising findings, when they reviewed medical literature -- all the 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. And these beliefs are frequently cited in the popular media. We didn't set out to become myth busters," said co-author Aaron Carroll, M.D., M.S., assistant professor of pediatrics and a Regenstrief Institute, Inc. affiliated scientist.

"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," said co-author Rachel Vreeman, M.D., a pediatrics research fellow.

The first belief they explored -- people should drink at least eight glasses of water a day. This advice 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. She thinks this myth can be traced back to a 1945 recommendation from the Nutrition Council that a person consume the equivalent of 8 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 in the recommended 64- ounce total. Drinking excess water can be dangerous, resulting in water intoxication and even death, the study authors note.

Dr. Vreeman and Dr. Carroll also explored the popular belief that we use only 10 percent of our brains. Frequently cited by everyone from physicians to comedians (Jerry Seinfeld) and erroneously credited to Albert Einstein, the 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.

Dr. Carroll and Dr. 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. With the help of these self proclaimed experts (perhaps the descendents of snake oil salesmen), one could tap into the 90 percent of the brain supposedly not being used....

via Medical Myths Even Doctors Believe.

There are several different origins of the 10% myth which is why, along with the fact that we simply choose believe things we like to believe,  it refuses to die.

No, for the Umpteenth Time, Your Brain Isn’t Hiding Superpowers From You ...

But Discover blogger and columnist Carl Zimmer has a piece this month that offers one possible  explanation for the phenomenon:

In the mid-1800s researchers discovered cells in the brain that are not like neurons (the presumed active players of the brain) and called them glia, the Greek word for “glue.” Even though the brain contains about a trillion glia—10 times as many as there are neurons—the assumption was that those cells were nothing more than a passive support system. Today we know the name could not be more wrong.

So, roughly 150 years ago, scientists studying the brain wrote off 91 percent of our brain as mere glue for the more important neurons that do the actual thinking. We now understand that they were wrong, but this strikes me as the sort of fact that can seep into the general culture and then become very difficult to dislodge.  The fact that psychics and TV shows through the years have propagated the myth surely can’t help. - discoverblogs

The 10% statement may have been started with a misquote of Albert Einstein or the misinterpretation of the work of Pierre Flourens in the 1800s. It may have been William James who wrote in 1908: "We are making use of only a small part of our possible mental and physical resources" (from The Energies of Men, p. 12). - link

... the belief is derived from debates during the early 1800s between those who believed that brain function could be localized to particular regions of the brain and those who believed that the brain acted as a whole. These debates centered around Franz Joseph Gall (1757-1828) and Johann Spurzheim (1776-1832) who developed the field of phrenology: the idea that specific human behaviors and characteristics could be deduced by the pattern and size of bumps on the skull. Not everyone agreed with Gall and Spurzheim. Marie-Jean-Pierre Flourens (1794-1867), an outspoken critic of phrenology, believed that although the cerebral cortex, cerebellum and brainstem had separate functions, each of these areas functioned globally as a whole ("equipotential"). Flourens supported his theories with experiments in which he removed areas of the brain (mostly in pigeons) and showed that behavioral deficits increased with size of the ablation. Although the work of Gustav Fritsch (1838-1927), Eduard Hitzig (1838-1907), Paul Broca (1824-1888) and Karl Wernicke (1848-1904) in the late 1800s provided strong datato counter the theory of equipotentiality, some scientists in the early 1900s appeared to once again favor the notion that the brain acted as a whole. - abuk

The above is likely the root of the self-improvement people in the early 1900s spreading the idea that we use only a small part of our brains.


One of the most important later sources of this myth is the work of Karl Lashley in the 1920's and 1930's. He taught a rat to run a maze, then systematically destroyed parts of its brain. The brain-damaged rat could still re-learn to run the maze. Lashley was looking for the brain's memory centers, but he what didn't know then was that the rat used various senses: sight, smell, & feeling, to navigate the maze.

Lashley destroyed the part of the brain that let the rat see, and the unfortunate creature still learned to find the cheese by smell and feel. He cauterized the part of the brain that let the rat smell, and it could still find the cheese by feeling its way.  This is a classic example of how wrong assumptions can lead to bad experimental design and wrong conclusions which take many years to correct. This is also another example of how much scientists hate rats. ;-)

"Karl Lashley was a stimulus-response behaviorist. He theorized that physical memory traces (engrams) must be made in the brain when learning occurs. These new connections of neurons were assumed to involve the cerebral cortex, as proven by studies conducted by Pavlov. In 1929, Karl Lashley wrote his famous monograph, "Brain mechanisms and intelligence." This work consisted of studies with rats and mazes. Lashley removed portions of the cerebral cortex, varying from 10-50% in an effort to study the role the cerebral cortex played in learning. - link

Lashley removed large areas of the cerebral cortex in rats and found that these animals could still relearn specific tasks. Lashley [wrongly] concluded that it was the amount of the brain – not the place that was important. - link