Nothing can wreck a vacation like arriving at your destination and being too exhausted to enjoy it. But that’s just what may happen if you experience jet lag—a disruption of your body’s natural 24-hour cycle, or circadian rhythm, which occurs when you travel across multiple time zones.

Fortunately, a few smart strategies can help.

A number of factors can make you more or less likely to experience jet lag, says neurologist W. Christopher Winter, M.D., medical director of the Sleep Medicine Center at Sentara Martha Jefferson Hospital in Charlottesville, Va., and a long-time sports and circadian rhythm researcher.

But typically, after traveling across time zones, your body’s internal “clock” can remain synced to your original time zone for several days. That can not only leave you fatigued, but make you feel disoriented and moody for several days as well—guaranteed vacation busters.

Here’s how to keep jet lag from derailing your summer trip.

When Your Body Clock Is Off-Kilter

Your body clock, which is set by exposure to light, signals when it’s time to wake up and when it’s time to sleep. But when you travel, it takes time for your clock to reset to your new location. That’s why while on vacation you might feel drowsy in the middle of the afternoon or be wide awake in the middle of the night.

The more time zones you cross, the more out of sorts you’ll probably feel. The general rule of thumb is that it takes one day per time zone to fully recover.

Women are more susceptible to jet lag than men, and the older you are, the harder it can be to adapt to new time zones, Winter says.

But the key factor is the direction of your travel. After traveling west on airplanes, most people only feel slightly jet-lagged, but flying east produces much more intense jet lag, according to Winter, who published a study in the International Journal of Sports Physiology and Performance in 2009 measuring the circadian advantage of baseball teams.

(Airplane flights going north or south usually don’t cause much jet lag, because travelers usually remain in the same or similar time zone.)

“Traveling west to east is harder because it is putting you in a position to do things before you are ready to do them,” says Winter. “It is a lot easier for us to delay doing something than it is for us to do it earlier.”

5 Ways to Prevent Jet Lag

Most long-distance travelers will experience some jet lag. And if you are going to stay in your new destination for only a day or two, you’re typically better off sticking with your home schedule than trying to adapt to a new one. But for longer trips, the following steps can help you rejigger body clock more quickly.

Change your bedtime beforehand. Start getting yourself acclimated to your new time zone before you even depart by going to bed 1 to 2 hours later (if you’re traveling west) and 1 to 2 hours earlier (if you’re traveling east) each day for a week.

That also helps ease the “first-night effect,” which can cause fitful slumber when you’re initially sleeping away from home. A study published in Current Biology in 2016 suggests that this may be because the left hemisphere of the brain remains more alert than the right during that first night in a new place.

Eat less en route. Winter recommends eating only lightly while you’re in transit—but returning to your normal meal size at your destination. Research suggests this can help you adapt to your new surroundings. And quickly getting on the eating schedule for the area you’re visiting may also help sync your body’s circadian rhythm to the new time zone, according to a brand new study in Current Biology.

During airplane travel, and at your destination, get plenty of water and other nonalcoholic liquids. Staying hydrated can also help fight fatigue.

Get some light after you arrive. “The more exposure to light, the quicker your recovery from jet lag,” says Marvin M. Lipman, M.D., Consumer Reports chief medical adviser. That’s because your 24-hour cycle is based on and influenced by sunlight and darkness.

But you need that exposure at the right time to reset your body clock properly. If you’ve traveled west from your home base, get it in the late afternoon. Do this in the morning if your trip takes you east.

Heading outdoors during those times is useful (don’t forget sun-protective strategies like sunscreen), but exposure to artificial indoor lighting can help as well.

And if you know that jet lag is often a problem for you during travel, consider light therapy to help you adapt, Winter says. Various over-the-counter light therapy devices, such as light boxes and goggles, are available at drugstores and online.

Winter says any of them may help curb jet lag. However, a study in the February 2016 Journal of Clinical Investigation found that intermittent flashes of light are more effective than continuous light at helping users adapt to new time zones more rapidly.

Limit caffeine and alcohol from start to finish. During an airplane flight, caffeine can cause you to be artificially awake and alcohol can create a false sense of fatigue. Both may hinder your adaption to the new time zone, Lipman says.

Once at your destination, you may be better off trying to force yourself to stay awake, rather than relying on coffee—though caffeine can help if you absolutely need to be alert, according to a small 2015 study.

And though alcohol may help you fall asleep faster, it can also lead to middle-of-the-night awakenings, slowing your ability to shake off jet lag.

Use caution with melatonin. Melatonin, a hormone naturally produced by the body when darkness falls, helps signal that it’s time to sleep. Its levels are reduced in the early morning, which helps our bodies know when to awaken.

Supplements of melatonin are sometimes used for jet lag and other sleep issues. And a 2002 review by the Cochrane Library, which looked at nine studies, found that melatonin decreased jet lag when crossing five or more time zones. But that was only when it was taken at bedtime in the new time zone.

When taken at the wrong time, the review notes, melatonin will actually delay adaptation to local time. Even when used at bedtime, 20 percent of readers in a recent Consumer Reports poll reported next-day drowsiness.

And remember that melatonin, like all dietary supplements (and unlike OTC and prescription drugs), is only loosely regulated by the Food and Drug Administration, Lipman notes. So you can’t be sure that what’s on the label is really what’s in the container.

In fact, a study published in February in the Journal of Clinical Sleep Medicine found that some melatonin supplements tested had far more or far less of the hormone than claimed on the label, and some also contained the brain chemical serotonin. Too much of either has the potential to cause significant side effects.

Finally, if you’re considering OTC or prescription sleeping pills to counter jet lag, you may want to read our Best Buy Drugs findings first.

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