You should drink at least eight glasses of water a day
This advice, often found in the popular press, probably originated from advice given in 1945 stating that a suitable allowance of water per day for adults is 2.5 liters (which is 10.14 cups). Drinking too much water can actually be harmful, resulting in water intoxication, hyponatraemia and even death.
We use only 10% of our brains
Erroneously credited to Albert Einstein, MRI and PET scans show that there are no dormant, inactive areas of the brain. Detailed probing of the brain has never revealed the non-functioning 90 percent.
Fingernails and hair grow after death
Johnny Carson even perpetuated this myth, but forensic anthropologist William Maples says no such thing occurs. However, there is a biological basis for the myth. After death, the skin around the hair or nails can retract, giving the impression that the nails or hair have grown when in fact the contrasting soft tissues just shrink.
Shaved hair grows back faster, coarser and darker
Clinical trials conducted as long as 80 years ago show that shaving has no effect on hair growth. More recent research proves that shaving doesn't affect the thickness or rate of hair growth. Because shaved hair lacks the fine taper seen on the ends of unshaven hair, it can appear to be more coarse.
Reading in dim light ruins your eyesight
Moms have long maintained that children who try to postpone bedtime by reading under the covers with a flashlight will need glasses. That's not true. Poor lighting can make it seem as if your eyes can't focus and it makes them feel dryer, but in fact such light won't permanently harm your eyesight.
Eating turkey makes you drowsy
Scientific studies do show that tryptophan, which is an amino acid present in turkey, is involved in sleep and mood control and can cause drowsiness. However, turkey doesn't contain enough tryptophan to knock you out.
Mobile phones are dangerous in hospitals
Hospitals may be plastered with warning signs against using cell phones, but not a single death can be attributed to such use. However, less serious incidents causing false alarms on monitors, malfunctions in infusion pumps, and incorrect readings on cardiac monitors, have occasionally been reported.