Have you ever flown on a vacation to Hong Kong or on business to Europe and wondered why you're ready for bed at noon or hungry at 3 AM? If so, you've experienced what many people call "Jet Lag."

Jet lag is caused by travelling at great speeds over many time zones. This unbalances the "circadian rhythms," or biological lock, which is set by the pineal gland (a tiny organ in the brain). Eye cells send light and darkness messages to this gland, which releases melatonin (a sleep-inducing hormone) in response to darkness. Thus, abrupt changes in time zones can upset melatonin production, which ultimately unbalances the body's sleep-wake cycle. These biological functions, combined with travel-related physical and emotional stress, cause jet lag.

Common symptoms of jet lag include headaches, irritability, upset stomach, sleeplessness, gastric discomfort, chills and inability to concentrate. Symptoms may be worse if you are travelling west to east (away from the sun), because light helps to preserve the body's equilibrium. Travel from east to west (to an earlier time zone) results in fewer jet lag symptoms, and travelling northward or southward does not affect the body's circadian rhythms at all.

Experts say it takes one day for every time zone crossed to recover from jet lag symptoms. For example, if you cross six time zones, it will take six days to feel like your old self again. Although there are many methods for minimizing jet lag, it is impossible to eliminate it entirely.

One suggested method of minimizing jet lag effects is to drink plenty of water before, during and after the flight. Some doctors recommend that you drink two eight-ounce glasses of water right before departure. Dehydration is highly possible during airplane travel, due to dry cabin air. It results in diminished blood flow to your muscles, reduced kidney functions and fatigue, all of which induce jet lag. You can prevent dehydration by drinking one liter of water for every six hours of flight in addition to beverages you drink with meals. Even if you may not be thirsty, it is important to drink water on a regular basis throughout the flight, because the body's thirst mechanism does not warn you early about dehydration.

Researchers are now looking into "light therapy," which is a method of re-adjusting the body's inner clock by controlling exposure to natural and artificial full spectrum light. One step in this strategy is to expose yourself to daylight as soon as possible once you arrive at your destination. Researchers also advise that you turn on your overhead light during your flight when it is daylight at your destination and turn off your light, or wear an eyeshade, when it is night there.

Another recent research strategy suggests melatonin capsules as a possible method of combating jet lag fatigue. Melatonin is a hormone marketed as a dietary supplement to assist with sleep and jet lag. Melatonin is a naturally produced in the pineal gland. Concentrations in the blood vary throughout the day. Levels are higher during the hours of sleep and lower during the waking hours. The amount of ambient light seems to control this variation.

Jet lag may be caused by the delay in synchronizing melatonin levels to match the hours of daylight and darkness after flying across time zones. So possibly readjusting melatonin levels could help with symptoms and sleep schedules.

Because melatonin is marketed as a dietary supplement, the Food and Drug Administration has no regulatory control over this product. Manufacturers are not required to prove the purity of their product or that the amount of drug stated to be in the product is accurate.

Studies on the use of melatonin for jet lag are promising, but further research is needed. First, the number of people studied thus far is very small. We don't know enough about side effects and interactions of the melatonin with other drugs and medical conditions. More study on the safety of melatonin is needed.

More conventional hypnotic sleeping medication could be used for one or two doses to regulate the sleep cycle in jet lag. Studies among USAF military pilots have recently demonstrated benefits for sleep and alertness with the short term use of the hypnotic zolpidem, marketed as Ambien, prior to desired sleep times. All medication, whether prescription or not, should be discussed with your doctor prior to use.

Aside from these interventions, you can take a number of simple steps to improve your ability to ward off jet lag. Improved Physical conditioning during the two to three weeks before your trip can help increase your stamina and thereby reduce the fatigue caused by travel-related stress. And according to reports from airline crews, it is helpful to take non-stop flights and to schedule your departing flight in the morning, when you are most ready for a full day's worth of activities.

In addition, following a few simple "do's and don'ts" can help:

Don't smoke, drink large amounts of alcohol, or take unnecessary medication while in flight.
Do get a decent night's sleep before your flight.
Do try to get some sleep during long flights.
Do exercise while on board the plane by stretching, walking about the cabin, and doing fitness exercises in your chair (like squeezing a tennis ball for seven counts and then releasing).
Much of the stiffness and the uncomfortable, dazed feeling following a flight is simply the result of sitting inactively for long periods of time. You may want to ask airline representatives if they can provide a brochure for in-flight exercises.

Finally, limiting your activities the first day after your arrival will yield more hours of fun and productivity in the end.

With high speed jet travel, the world has certainly become a smaller place. Incorporating these recommendations into your trip plans should help take the "lag" out of jet travel.

Have a great trip!