9 medical myths explained
December 20th 2008 21:04
"We use only 10% of our brains."
We use only 10% of our brains
We all use all of our brain. This myth is commonly thought to be due to a misquotation of Albert Einstein or a misinterpretation of Pierre Flourens (from the 1800s). In modern operating theatres, neurosurgeons carefully map the brain before removing tissue during operations (for example for epilepsy or tumours) to ensure that essential areas of the brain are not damaged.
Sugar makes children hyperactive
Many credible scientific trials have examined how children react to diets containing different levels of sugar and not one study has detected differences in behaviour between the children who had sugar and those who did not. This includes sugar from sweets, chocolate and natural sources. Scientists have also studied parents and determined that, when parents think children have been given a drink containing sugar (even if it is really sugar-free) they tend to rate their children’s behaviour as more hyperactive.
Hangover cures
We all swear by one, or know someone who does. We all have a secret, anecdotal, family-hand-me-down guaranteed, hangover cure, or know someone who does. They're all wrong. Every last guaranteed one of them. There is no known hangover cure.
You lose most of your body heat through your head
This myth has been traced to a US army survival manual from 1970 which said that a hat should be worn when it is cold because "40 to 45 percent of body heat" is lost from the head. It isn't. The best scientific evidence is that up to 10 per cent of body heat can be lost through the head.
The incidence of suicides increases during holiday periods
Not true. One study from Japan that looked at suicides over 16 years showed that the rate of suicide was lowest in the days before a holiday and highest in the days after the holiday. Another study in the US of suicides over a 35-year period concluded no increase before, during or after holiday periods. The study results are different, but they agree on one thing: the incidence of suicide does not increase during holiday periods.
People should drink at least eight glasses of water a day
Professor emeritus of physiology at Dartmouth Medical School, Heinz Valtin, among others, reports no supporting evidence for this popular myth. Professor Valtin, a kidney specialist, believes the idea may stem from a US Food and Nutrition Board of the National Research Council recommendation that humans consume "1 milliliter of water for each calorie of food" ingested. This would amount to between 64 and 80 fluid ounces a day. In its next sentence, the board stated, "Most of this quantity is contained in prepared foods," but the second sentence may have been ignored over time.
Hair and fingernails continue to grow after death
This is an optical illusion. It is caused by dessication of the skin in death. As the skin dries out, it recedes, giving the appearance that nails and hair are getting longer. They're not - the skin is shrinking. This myth is the subject of a quip by US television personality Johnny Carson, who said, "For days after death hair and fingernails continue to grow, but phone calls taper off."
Shaving hair causes it to grow back faster, darker, or coarser
If you have never shaved your legs, the hair on them is fine and soft. Shave that off, and what grows back is immediately hard and scratchy, right? Right, and there is the cause of the myth. The scratchiness is natural as the hair is short. It will be the same each time you shave. Once hair grows back fully, it will the fine and soft again, just as before. This is the same for all hair, be it on men's faces or on women's legs.
Reading in dim light ruins your eyesight
Dim lighting can cause stress in the eye, but the effects will not be permanent. According to studies by Rachel C Vreeman, a fellow in children’s health services, and Aaron E Carroll, an assistant professor of paediatrics, "Suboptimal lighting can create a sensation of having difficulty in focusing. It also decreases the rate of blinking and leads to discomfort from drying. The important counterpoint is that these effects do not persist."
British Medical Journal, www.bmj.com, www.dailymail.co.uk, www.guardian.co.uk, www.news-medical.net, www.sciencedaily.com, American Journal of Physiology, www.snopes.com
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