Keith Mulvihill
Events such as traveling between time zones can throw off the body's circadian rhythm, or internal clock. A proposed solution to re-establish the timing, widely circulated in 1998, was to shine bright light on the back of the knees. But two Harvard researchers have now disproved the solution.
The circadian rhythm controls many of the body's functions, including sleep, hormone regulation, and temperature. The internal "clock" receives its signals from light transmitted into the eye. Without these eye functions, the clock cannot be reset. This is why light beamed onto the back of the knee was highly questionable.
The Harvard researchers exposed healthy volunteers to back-of-the-knee illumination for ten days in a laboratory - same as the original study that proposed the solution. However, they shielded against some of the original study's shortcomings, ensuring, for instance, that their subjects' eyes were entirely shielded from the light.
The back-knee illumination, they concluded, had absolutely no effect.
Science July 26, 2002;297:571
I was quite surprised when this concept of light on the back of the knee was first published in the prestigious journal "Science" four years ago. Now it appears to be untrue.
Meanwhile, though, the principles about sleep in relation to your rhythms are still entirely valid. We have an epidemic in the U.S. of people not sleeping enough. The average American sleeps only 7 hours. People were sleeping 9 hours per night prior to the invention of the light bulb, which allowed us to transform night into day.
Most people do not realize the huge risk that constantly neglecting our sleeping needs poses to our health. As the article above suggests, our bodies are tied in to very powerful biorhythms, and if we violate them we are asking for trouble. There is also a profound relationship between sleep deprivation and insulin sensitivity.
The bottom line is, you should try to sleep at least 8 hours a night. And you should sleep in a completely dark room -- as dark as is practically possible -- as any outside light has the potential to disrupt your melatonin rhythms.
If you are interested in more information on this fascinating subject, check out the book Lights Out: Sleep, Sugar, and Survival by T. S. Wiley, Bent Formby, PhD. It is an excellent resource. Nearly one third of the book references peer-reviewed literature, so it is very carefully documented.
The authors believe that it is primarily light, not what we eat or whether we exercise, that causes obesity -- and diabetes, heart disease, and cancer.
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