From Doctor Weil:
your doctor how much water you should drink or why you couldn’t keep
your eyes open after Thanksgiving dinner, and you’re likely to get the
same misinformation your mother-in-law might dispense. A study
published in the December 2007 British Medical Journal
tweaked physicians on their acceptance of some widespread medical
beliefs that might now be reclassified as old wives’ tales. Here’s a
- Drink at least 8 glasses of water a day: The
researchers who conducted the study could find no clinical evidence to
support this notion. But they did dig up an article from the November
2002 American Journal of Physiology that documented the lack
of evidence behind this popular recommendation. You do need to be well
hydrated, but research suggests that the liquids most people drink
daily – juice, milk, and decaffeinated beverages – will do the trick.
Your best bets are purified water, diluted fruit juice, tea, and sparkling water flavored with fruit juice.
- We use only 10 percent of our brains:
This is a real oldie that traces its history back to 1907, but didn’t
originate, as once believed, with Albert Einstein. Now that we know
much more about neuroscience than we did 100 years ago, we can say for
sure that we use much more than 10 percent of the brain, say the BMJ
researchers. In fact, high-tech methods of studying the brain have not
identified any inactive areas.
- Hair and fingernails continue to grow after death:
This disturbing, gruesome image is pure “moonshine” according to
forensic anthropologist William Maples, who was quoted in the BMJ
study. However, he explained that dehydration of the body after death
can cause retraction of the skin around hair and nails, giving the
illusion that they have grown. All tissues require energy to sustain
their functions, and no such thing is possible once the mechanism that
promotes normal growth shuts down at death.
- Reading in dim light ruins your eyesight: You
can get eyestrain and have difficulty focusing when trying to read in
poor lighting, but these symptoms have no permanent effect on eyesight.
One current theory holds that nearsightedness (myopia) might be caused
by reading in dim light or holding books too close to the face. But
consider this: rates of myopia are increasing and are higher
now then they were centuries ago when people read by candlelight.
What’s more, the BMJ researchers found hundreds of expert opinions that
conclude that reading in dim light doesn’t permanently hurt your eyes.
- Shaving causes hair to grow back faster or coarser: No,
it does not. This popular notion was disproved as early as 1928 and
more recent studies have confirmed that shaving has no effect on hair
growth (or regrowth), write the BMJ investigators. They speculate that
when shaved hair regrows, it lacks the fine taper seen at the end of
unshaven hair, making it appear coarser. And the fact that it hasn’t
been exposed to light may make it seem darker than other hair.
- Mobile phones are dangerous in hospitals: The
BMJ credits this widespread belief (and the origin of those signs in
hospitals warning against the use of mobile phones) to a Wall Street
Journal article citing a medical journal report of more than 100
incidents of suspected electromagnetic interference with medical
devices before 1993. But studies in England and the U.S. have found
little in the way of interference and few serious effects. The BMJ
cited a 2007 study that showed no interference at all in 300 tests in
75 treatment rooms. Indeed, the journal reported on a survey of
anesthetists that showed use of mobile phones by physicians was
associated with a reduced risk of medical error or injury
resulting from delays in communication. Let’s see how long it takes
hospitals to react to these findings and change their policies with
regard to cell phone use.
- Eating turkey makes people especially drowsy: Not
so. Here, the myth is that the tryptophan in turkey causes the
drowsiness. This amino acid is known to cause drowsiness, but the truth
is that there’s as much tryptophan in pork and cheese as there is in
turkey. What’s more, as the BMJ researchers noted that for tryptophan
to promote sleep, you need to ingest it on an empty stomach (with no
protein present) – something that’s unlikely at Thanksgiving or
Christmas dinner. Other factors are probably to blame for post-meal
drowsiness: any big meal can make you sleepy because of a decrease in
blood flow and oxygenation to the brain. And then, of course, there’s
The researchers said that they selected the seven
myths above because they had heard them so often that they thought they
were true or might be true. They learned that they could be wrong and
“need to question what other falsehoods we unwittingly propagate” in
the practice of medicine.