DALLAS - For many travelers who cross several time zones, the exhilaration of taking in sights such as the Eiffel Tower or the pyramids of Egypt is quickly tempered by the grogginess of jet lag.

Veteran flyers often have their own remedies to overcome those signals from the body that it's time for sleep. But an Oregon researcher recently detailed in The New England Journal of Medicine three basic strategies for overcoming jet lag:

1. Reset the circadian clock that tells a person to stay awake during the day and sleep at night. You can do this by taking the sleep-inducing hormone melatonin, timing your exposure to bright light, or both.

2. Adjust your sleep schedule. Take short naps when you are sleepy the first few days after arrival. If you can, shift your sleep schedule by a couple of hours before travel.

3. Use medications to get to sleep or stay awake. Or turn to the old reliable remedy for keeping your eyes open: caffeine.

"We have mechanisms to adjust our clocks, but those mechanisms have to be called on to go into high gear," says Dr. Robert Sack, a psychiatry professor at Oregon Health & Science University in Portland, Ore., whose article takes a science-based look at jet lag remedies.

Sack says melatonin is the most extensively studied jet lag treatment, with a majority of double-blind, placebo-controlled trials showing it helped symptoms.

"Its effect is based in good science," Sack says. He said the U.S. Food and Drug Administration has not evaluated melatonin, but no significant adverse effects have been reported.

Melatonin is sold as a nutritional supplement in the United States, and no prescription is needed for it.

The FDA has not approved any drugs for jet lag, but drugs that help with alertness or insomnia can alleviate jet lag, Sack says.

For eastward travel, from the United States to Paris for example, a traveler might go for a walk in the sun and then sip a latte at an outdoor cafe shortly after arrival. Travelers who are unbearably sleepy as the day wears on should take a short nap, Sack says. Then take melatonin - a dose of 0.5 to 3 milligrams - before heading to bed, and hopefully you'll be adjusted to your new time zone within a couple of days.

For westward flights - such as Europe back to the United States - travelers should expose themselves to bright light in the evening to help stay up later; then, when their eyes pop open before 5 a.m., take a low dose of melatonin.

"Your internal dawn is occurring before you want it to," Sack says. "It's easier to lengthen your day, which is what you do when you travel westward."

While trouble sleeping or waking up is the main symptom of jet lag, travelers can also experience irritability, difficulty concentrating and upset stomachs, says Sack, whose research was published in February.

Clayton Cowl, chief of aerospace medicine at the Mayo Clinic in Rochester, Minn., says that jet lag can be a difficult condition to pin down since it affects different people in different ways and can be influenced by several factors.

"Everyone will seem to have a signature strategy that will work for them, and I think this article helps to identify the palate of things that are safe and for the most part effective," Cowl says of Sack's findings. "Unfortunately, there's not just one straight recommendation: Take these two pills and you'll be fine."

For most patients, jet lag results in "a sense of malaise," Cowl says. "You just don't quite have that energy."

Dallas management consultant Andrew Watterson, who has been traveling frequently overseas for work for the past 15 years, says that when he started, he made the mistake of not sleeping on the flight over and got a good dose of jet lag.

"In reality, I didn't know how powerful it would be," says Watterson, 43, of Dallas.

Like most frequent travelers, he's now got a system. One thing he's noticed is that on the day of arrival, he vacillates between sleepiness and alertness, so he plans his day accordingly, making sure not to schedule any important appointments around 3 p.m. Instead, he takes a coffee break.

Debbie Bauer, who has been flying as a flight attendant for American Airlines for 32 years - internationally for the past 23 - has had her share of jet lag. For instance, after spending about 72 hours making the trip to New Delhi, India, and back, she usually gives herself the day after getting home to recover - doing light chores but making sure to bring a list when she goes grocery shopping.

"I don't do anything that requires careful thought," says Bauer, 53, who lives in Arlington, Texas. "It takes its toll on you."