Second-year graduate student Carmen Yip traveled to Hong Kong over winter break and, like many travelers, suffered from jet lag. That meant going through fatigue, loss of appetite and trouble sleeping. But after new research from a University biology professor, Yip and fellow travelers may have one less reason to dread crossing time zones.
To prevent the common digestive problems caused by the body's reaction to overseas time adjustments, Biology Prof. Michael Menaker and his team of scientists suggest that travelers alter their meal times before stepping on the plane.
So if someone is anticipating a trip to Paris, for example, eat on Paris time prior to departure, he says. The slight adjustment could make all the difference for an enjoyable visit.
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Our body has an internal clock that works on a 24-hour cycle. Many of the symptoms of jet lag are caused by the fact that when you travel across time zones, the length of your day changes.
The body's main internal clock, located in the brain, controls the body's circadian rhythms, which are behaviors such as sleeping and eating that cycle every 24 hours. The brain's circadian rhythms are set to the light-dark cycle of the environment - for instance, telling the body to sleep when it's dark.
Before Menaker's team research, scientists believed circadian rhythms only were controlled in the brain.
The team, however, found that other organs also have their own rhythms. They focused on the circadian rhythms of the liver.
What they found is that even if the brain clock adjusts to the light-dark cycle of a new environment, the other clocks may not. This explains some of the symptoms of jet lag, including gastrointestinal problems such as diarrhea.
"People who do shift work have GI tract symptoms," Menaker says, further showing when the circadian rhythms of the liver are disturbed, digestion problems may result.
By appropriately adjusting meal times, the liver's circadian rhythm would adjust more quickly and, more importantly, help prevent the digestive problems of jet lag.
Travelers like Yip, who lost her appetite when she returned to the United States from Hong Kong, would benefit from following Menaker's advice.
The team used rats to test their theories. The rats, which are nocturnal, were fed during the day instead of at night. The researchers found that in response to these changes in mealtime, the circadian rhythms of the liver were altered.
Using a fluorescent protein to monitor the phase of the liver's rhythm, they found that the circadian rhythms were shifted.
Since these experiments were performed on rats, they cannot be translated directly to humans. But it is "very unlikely these findings don't have any implications" for humans, says Menaker, who hopes to conduct more research in the future.
Kristin Clontz, assistant professor of Internal Medicine, cautioned that "studies in lab animals don't always correlate" with humans.
Clontz says since these findings have not been demonstrated in humans yet, it is not routinely recommended. Currently, she said, travelers are advised to adjust their sleeping times prior to their trip.
On the other hand, Gene Block, director of the Center for Biological Timing, says these findings are important in refuting the conventional wisdom on how to combat jet lag.
Previously, the focus was on controlling what times of day you were exposed to light. Block says there "may be better ways to rapidly resynchronize body rhythms."
Menaker stressed that other than jet lag there are several other medically important applications of his research, such as for the treatment of liver cancer. Because the organ has its own internal clock, the liver would be more sensitive to treatment at certain times. By changing meal times the liver could be put in the most sensitive phase for treatment, Menaker says.
Altering meal times may offer a simple, non-invasive method for preventing the woes of jet lag, if it can live up to the promise it has shown in rats.
Remember this the next time you jet across the Atlantic.
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