The old joke about your luggage arriving in better shape than you do after a long flight is funny only if you're not suffering jet lag.
For years, jet lag -- that out-of-sync exhaustion that strikes after travel across too many time zones -- has befuddled and intrigued researchers. They know it's a temporary disruption of normal circadian or body clock rhythm, but they don't know how to prevent it.
In recent years, scientists have made some interesting advances in minimizing the effects of high-speed jet travel. Researchers have realized that jet lag is not just a problem of the brain "clock" being out of sync, as researchers believed for years, but also a disruption of other parts of the body that requires a multi-pronged approach.
Although some travelers seem more resistant to jet lag, no one's sure exactly why or which characteristics these seemingly immune fliers share.
Traditional wisdom has it that jet lag occurs when your brain clock becomes out of step with the time at the destination. But "it's more complicated than that," says Gene Block, a professor of biology at the University of Virginia, Charlottesville, and a circadian rhythm researcher. Scientists know that the body clock in the brain's hypothalamus -- which regulates body temperature, metabolism and other activities -- must resynchronize after travel across several time zones. "Only in the last few years have we discovered 'clocks' in other parts of the body," he says.
Your liver and spleen have clocks, Block says. The one in the brain may be the master clock, but several other body clocks in various organs and tissues disrupt the body's circadian rhythms too and contribute to that dragged-out feeling.
The brain must synchronize, of course, but scientists now think that the other body clocks must also re-regulate themselves to the destination time. "Different clocks take different amounts of time to resynchronize," Block says.
Suppose you are flying from Los Angeles to Paris. "The next day, some body clocks have resynchronized to Paris time, and some have not," Block says. You won't feel completely normal, he says, until all the body clocks adjust to the new time zone.
Block and Michael Menaker, another University of Virginia biologist, think adjusting mealtimes to your destination before a trip can help reset your digestive system clocks. That suggestion is based on a study, published in the journal Science, in which they simulated jet lag in rats and then changed the animals' feeding cycles.
