Harness the power of light
Bright light helps keep our internal clock in sync with the outside world, traveling through specialized cells in the retina and signaling the part of the brain that sets the body’s master schedule. So, for longer trips, seek out or avoid bright light at specific times, said Dr. Olson. Starting a few days before your trip, gradually shift the light and dark times of your origin toward that of your destination, using dark glasses, sunlight or other light sources.
In the first few days of your trip, figuring out the best times to get light can be tricky. Let’s say you take an overnight flight from New York to London, arriving at 7 a.m. Your brain may still feel as if it’s 2 a.m., and getting bright light right away could confuse your internal clock. In this case, you may want to put on dark glasses for a few hours, then go out in the sun when it is closer to your waking time at home, extending your London day.
On long trips to Asia — when day and night are reversed — it is often easier to shift your cycle backward, said Mickey Beyer-Clausen, chief executive of Timeshifter, which makes a jet lag app of the same name. For example, when flying nonstop from New York to Tokyo, which is 13 hours ahead, think of it as being 11 hours behind (jet lag does not consider the international date line). That means if you land at, say, 2 p.m. in Japan — 1 a.m. in New York — you need to counter the fact that your New York brain is winding down for sleep. This means seeking out bright light all afternoon, especially in the evening, until bedtime in Japan. You can also get a head start on adapting to Japanese time if you go to bed and seek out light later than normal for two nights before you leave New York.
Online tools like Jet Lag Rooster and Timeshifter help create a customized schedule based on variables like time zone differences, departure and arrival times, and other factors.
If you are having trouble getting to sleep earlier in anticipation of traveling east, Dr. Kapur suggests taking one milligram of over-the-counter melatonin about four hours before bed, up to three days before the trip. (Melatonin is a substance that is produced naturally in the body as night falls, signaling that it is time to go to sleep.) This small dose is best for reducing jet lag, Dr. Olson said, because studies show a larger dose doesn’t necessarily work better and is more likely to produce side effects. Travelers should be aware that as a dietary supplement, melatonin is not regulated by the Food and Drug Administration.