Medical Myths Even Doctors Believe

Most are harmless. But when doctors start believing medical myths, perhaps it's time to worry.

And so here they are:

Myth 1: We use only 10 percent of our brains.
Fact: ...The myth probably originated with self-improvement hucksters in the early 1900s who wanted to convince people that they had yet not reached their full potential.

Myth 2: You should drink at least eight glasses of water a day.
Fact: ...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. Over the years, "fluid" turned to water. But fruits and vegetables, plus coffee and other liquids, count.

Myth 3: Fingernails and hair grow after death.
Fact: ...it's impossible. As the body’s skin is drying out, soft tissue, especially skin, is retracting. The nails appear much more prominent as the skin dries out. The same is true, but less obvious, with hair. As the skin is shrinking back, the hair looks more prominent or sticks up a bit.

Myth 4: Shaved hair grows back faster, coarser and darker.
Fact: ...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. Hair that's just emerging can be darker too, because it hasn't been bleached by the sun.

Myth 5: Reading in dim light ruins your eyesight.
Fact: ...It can cause eye strain and temporarily decreased acuity, which subsides after rest.