It's an uncomfortable feeling: you're loudly proclaiming a "scientific fact" and are suddenly assailed by a creeping sense of doubt. Did you learn it in science class, or was it just something your grandmother used to say? At least now we have Wikipedia if we want to check.
A huge number of myths and superstitions seem to collect around health and medicine. Everyone knows that eating late at night makes you fat, right? We're sure that sugar makes kids hyperactive, aren't we? And surely it's important to wear a hat in winter, since we lose most heat through our heads? Researchers from Indianapolis have now revealed that none of these beliefs are true.
One study did find that overweight women tended to eat later in the day. But they were also eating more overall, which is what really made the difference. Studies have also shown that your patterns of energy usage, which vary during the day and at night, aren't affected by the timing of meals.
More than a dozen good-quality studies have failed to find any link between sugar in children's diets and hyperactive behavior. So, why do parents associate sugar with hyperactivity? In one study, parents were told that their children had been given sugary drinks, and went on to rate their children as hyperactive. What they didn't know was that their children had really been given a sugar-free drink. The difference was in parents' minds.
The belief that most heat is lost through the head is particularly widespread. Even the U.S. Army field manual tells soldiers that they lose up to 45 percent of their body heat through their heads. This misconception probably comes from an experiment that measured heat loss in people wearing arctic survival suits, but no hats. Naturally, they lost most heat through their heads. But any uncovered part of your body loses heat at the same rate, so if you're wearing a bathing suit, the heat loss through your head is about 10 percent.
If we really lost 45 percent of our body heat through our heads, going without a hat would feel just as cold as going out without wearing pants.
What you need to know. It's worth checking whether popular medical "facts" are actually true. It's always better to think for yourself; after all, it's not as if we only use 10 percent of our brains. Is it?
—Philip Wilson, patient editor, BMJ Group
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