By Emily Sohn

The Washington Post

Jet lag is a tough problem. High-speed plane travel to a location out of sync with your body's internal clocks can cause more than sleepiness. Symptoms of jet lag include irritability, disorientation, nausea, gastrointestinal distress and trouble concentrating.

Our bodies have fine-tuned timekeeping systems that don't adjust immediately upon arrival. We are all different, so there is no one-size-fits-all advice.

“It's hard to come up with any general recommendations for jet lag, because it depends on how many time zones are crossed, and in which direction, and on when people usually sleep at home and when they want to be sleeping in the new time zone,” said Charmane Eastman, founding director of the Biological Rhythms Research Laboratory at Rush University Medical Center in Chicago.

But planning ahead can make a difference.

“The more days people spend shifting their circadian clocks before the flight, the fewer days they will have of jet lag after the flight,” she said.

Inside the brain's hypothalamus is the suprachiasmatic nucleus, which contains cells that control the body's circadian rhythm. In most people, this master pacemaker runs slightly longer than 24 hours. Their urge to sleep naturally drifts later over time, a night-owl tendency that makes it easier to travel westward: Going back in time requires staying up longer to adjust to the new zone.

The adjustment inside our body happens quickly. According to some estimates, the typical person's internal clock shifts about 92 minutes later each day after a westward trip, but 57 minutes earlier after going east. For the minority of people who are early birds with clocks that are shorter than 24 hours, adjusting to going east is easier, said Sabra Abbott, a neurologist at the Northwestern University Feinberg School of Medicine in Chicago.

It’s not the one main body clock that has to adapt to a new schedule. Every organ and tissue has its own timekeeping mechanisms. Even as the main clock adjusts, mismatch might continue between clocks in other organs. Over time, people who do shift work or travel frequently can suffer health consequences from misalignment of internal clocks. Research suggests risks include obesity, diabetes, cancer and heart disease.

Although a single trip is unlikely to carry long-term health risks, Abbott said, jet lag can impair safety and performance, depending on what a traveler is doing upon arrival. Despite wide-ranging anecdotal advice that is often conflicting or seemingly impossible, studies suggest two basic strategies can help: carefully timed exposure to bright light and, sometimes, over-the-counter melatonin. Be aware it's easy to make mistakes with both approaches.

Through laboratory studies that involve abruptly shifting people's sleeping schedules and measuring how quickly their clocks adjust, Eastman found inadvertently getting light at the wrong times after arrival can push the body clock the wrong way or make it stall, even if you follow common advice — such as getting morning exposure to light at your destination or immediately going to bed at the new normal bedtime.

Doing it right can speed up the process of adjusting. Eastman has developed a system for creating individualized schedules that include exposure to bright light and to darkness. She uses the method starting a few days before she leaves on a trip and says she manages to cross time zones without jet lag. Online calculators for planning ahead, such as, offer similar plans.

Studies suggest melatonin, which our bodies release in tiny amounts near bedtime, can help when taken in the afternoon before going east or in the morning before heading west. Drugstores sell pills that contain five or 10 milligrams of melatonin, Abbott said, far more than our bodies make.

Taking large doses can make you sleepy. The hormone can also remain in your bloodstream when you get up. In some cases, as little as 0.3 to 0.5 milligrams is enough. It's a tiny fraction of what some pills contain.

“It's one of those things where taking more of it doesn't help,” Abbott says. “If it doesn't work, it means you took it at the wrong time.”

Researchers warn against some common pharmaceutical strategies for jet lag. Mixing Ambien and alcohol is a bad idea, Abbott says. Naps when needed are OK. Symptom-masking aids such as caffeine and sleeping pills have their place, though they won't make your internal clocks shift faster.

People develop superstitions about jet lag, believing something odd worked for them, even if they happened to get the light exposure right. In Eastman's lab studies, when exposures to light, darkness and melatonin are controlled, some people's bodies adjust quicker.

Shifting the clock may get harder with age. Such variances may explain why friends can swear by strategies that do not work for you.

“The best advice is always just to try to do as much as you can to adapt to the new schedule right away,” Abbott said. “It's sending a message that this is the new schedule.”