Jet lag is one of the banes of modern life, and researchers are beginning to take it seriously. Leading the pack of potential cures is the hormone melatonin, which the body produces when deprived of light. High melatonin levels tell you it's time to sleep, whether you're in bed or not. Low levels incite wakefulness.

For years, scientists have debated whether supplements of melatonin fight jet lag. That's probably because people haven't been taking it at the right time, says Charmane Eastman of Rush University Medical Center in Chicago. In a study reported in the journal Sleep, she found that people with artificially induced jet lag slept substantially better on doses of melatonin even as low as .3 mg. The trick is to take the pill half an hour before bed only if your body thinks it's the wrong time of day to sleep. Otherwise, your body's already producing enough.

A good rule of thumb is to stick with the lowest dose that works.

• On eastward red-eye flights, keep the shutters pulled or wear an eye mask in the morning.
• Traveling westward on daytime flights, try to get a window seat on the plane's sunny side.
• Use properly timed bright lights—which simulate sunlight—to shift your circadian rhythm.
• Late afternoon exercise raises body temp and keeps you awake longer. Use it to stay up, avoid it to chill out.

Product: Melatonin | Price: $5.95/100 | Result: Resets body clock

Product: Dark sunglasses | Price: Varies | Result: Resets body clock

Product: Bright-light box | Price: $150 to $500 | Result: Resets body clock

Product: L-tryptophan | Price: $39.95 (100 pills) | Result: Makes you drowsy

Product: Lunesta | Price: Varies | Result: Knocks you out

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