Seven Medical Myths

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How much truth is there to all that hand-me-down medical advice that even doctors don’t dare refute? In the British Medical Journal, U.S. doctors Rachel Vreeman and Aaron Carroll examined whether these common medical beliefs should really be doing the rounds.

“READING IN LOW LIGHT RUINS YOUR EYESIGHT”

Reading in dim light may make your eyes sore, but it won’t ruin eyesight as commonly believed. Turns out that this soreness is only temporary; there are no permanent negative physiological effects on your eyes. A study published in the British Medical Journal in 2002 suggested that such straining of the eyes could result in myopia (short-sightedness) based on the fact that the incidence of myopia has increased in the past few centuries. This may be the case, but we no longer rely on candles or gas lights to read, so dim lighting cannot be the reason for this increase in short-sightedness.

“SHAVED HAIR GROWS BACK FASTER AND DARKER”

To wax or to shave? Waxing advocates will tell you that shaving causes hideous stubble to grow back faster and darker than the hair that existed before. However, since 1928, several clinical trials have shown that shaving has no effect on hair thickness or rate of growth. So why do shaved legs feel less smooth than waxed legs a week later? The stubble that comes after shaving grows without the taper seen at the ends of unshaven hair, creating the illusion of increased coarseness.

“DRINK EIGHT GLASSES OF WATER A DAY”

Do we really need to drink eight glasses of water a day to stay healthy? This thinking may have originated from a recommendation made in 1945 when the U.S. National Research Council advised that a suitable allowance of water for adults is 2.5 L daily – equivalent to about eight glasses. Existing studies show that we obtain a lot of fluid through drinking juice, milk and hot drinks, and by absorption through food, negating the need to drink that much water. In fact, ingesting very large volumes of water – around 20 L - can actually be dangerous, causing blood dilution and eventually death, particularly if your kidney function is subnormal or you suffered a recent head injury.

“YOU ONLY USE 10 PER CENT OF YOUR BRAIN”

While certain people we know might seem to use only 10 per cent of their brains, advances in neuroscience have proved that lesions to any part of the brain can have negative effects on behavioural and mental capabilities. In his book, Mind-Myths: Exploring Popular Assumptions About the Mind and Brain, the late neuroscientist, Barry Beyerstein wrote about the origin of this myth and the evidence against it. We now know that certain functions are localised in different regions of the brain, which means that we may only use a small part of our brain to perform a certain task, and the active region of the brain used depends on the task performed. However, detailed anatomical and brain imaging studies have failed to identify this so-called “non-functioning 90 per cent” of the brain.

“MOBILE PHONES INTERFERE WITH MEDICAL EQUIPMENT”

In June 1994, The Wall Street Journal published the headline, “Clutter on airwaves can block workings of medical electronics” after a journal article in Health Facilities Management cited over 100 reports of suspected mobile phone interference with medical devices. There is some evidence from early studies that interference could happen at distances of less than one metre, but technological improvements have eliminated this. A 2007 study published in Mayo Clinic Proceedings found no mobile phone interference with medical electronic equipment in 300 tests of 75 treatment rooms.

“HAIR AND NAILS GROW AFTER YOU DIE”

Don’t believe everything you may see on CSI – hair and fingernails do not continue to grow after death. There is actually a biological basis for this myth, however, as forensic anthropologist William Maples explains in his novel Dead Men Do Tell Tales: The Strange and Fascinating Cases of a Forensic Anthropologist. After death the skin around the hair or nails dehydrates and recedes, giving the appearance of increased length. In fact, the growth of hair and nails requires complex hormonal processes, which do not occur post-mortem.

“EATING TURKEY MAKES YOU SLEEPY”

Don’t eat turkey and operate heavy machinery, as it may make you drowsy, suggests the common wisdom. Turkey meat contains the chemical tryptophan, an essential amino acid involved in making serotonin, a neurotransmitter that regulates sleep and mood control. But chicken and minced beef also contain similar levels of tryptophan (approximately 0.31 g per 100 g) while food such as cheese contains more tryptophan per gram than turkey. What is actually making you sleepy after a big Christmas dinner is probably not the turkey, but alcohol, bad conversation, relatives and a carbohydrate-laden meal.

by Michelle Kovacevic
Cosmos Online