A review of some of the most common medicine-related myths published in this week’s Christmas issue of the British Medical Journal, concludes that humans don’t need to drink eight glasses of water a day, as well as debunking other medical myths.
Other medical myths debunked in the study:
- Eating turkey makes people especially drowsy: Evidence shows that tryptophan, a chemical in turkey, can cause drowsiness, but turkey contains the same amount of tryptophan, gram per gram, as chicken and ground beef, said Dr. Rachel Vreeman, co-author of the study and a fellow in children’s health services research at Indiana University School of Medicine in Indianapolis.
Any big meal or holiday feast can make people sleepy because blood flow and oxygenation to the brain decrease. Wine also doesn’t help.
- Hair and fingernails keep growing after death: Creepy, but not so. It’s an optical illusion, Vreeman says. After death, skin and other soft tissue dries out. The shrunken skin pulls back and retracts, making fingernails or hair more obvious or prominent.
- Reading in dim light ruins your eyes: It can make eyes feel dry and irritated, because people blink less when reading in sub-optimal light. It can also cause a temporary decrease in acuity, or how well you see.
- Shaving causes hair to grow back faster or coarser: As early as 1928 a study showed shaving had no effect on hair growth. Shaving removes the dead part of hair, “not the living section below the skin’s surface” so it’s unlikely to affect how fast it grows back. What’s more, “shaved hair lacks the finer taper seen at the ends of unshaven hair, giving an impression of coarseness.”
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