7 Common Medical Myths Debunked

1. Medical Myth: Drink at least eight glasses of water per day.

Reality: There's no evidence that you have to drink that much water to assure adequate fluid intake -- and drinking too much water can be unhealthy.

2. Medical Myth: We use only 10% of our brains.

Reality: Most of the brain isn't loafing. Detailed brain studies haven't found the "non-functioning" 90% of the brain.

3. Medical Myth: Hair and fingernails continue to grow after death.

Reality: Hair and fingernails don't keep growing after death. But it may seem that way because dehydration can make the skin shrink back from hair and nails, making them look longer.

4. Medical Myth: Reading in dim light ruins your eyesight.

Reality: Dim light isn't great for focusing, but it's "unlikely to cause a permanent change in the function or structure of the eyes," Vreeman's team writes.

5. Medical Myth: Shaving causes hair to grow back faster or coarser.

Reality: "Shaving does not affect the thickness or rate of hair regrowth," write Vreeman and colleagues. But shaved hair doesn't have the fine taper of unshaved hair, making it seem coarser.

6. Medical Myth: Mobile phones are dangerous in hospitals.

Reality: "Rigorous testing in Europe found minimal interference and only at distances of less than one meter [about 3.28 feet]," write the researchers. But that may be a point of controversy. In September, Dutch doctors reported that cell phones may interfere with critical care equipment and shouldn't be used within a meter of medical equipment or hospital beds.

7. Medical Myth: Eating turkey makes people especially drowsy.

Reality: Turkey isn't all that rich in tryptophan, the chemical linked to sleepiness after eating turkey. But eating a big, decadent meal can cause sleepiness, even if turkey isn't on the menu.