There's a mind-bogglingly simple reason why certain trips give you such bad jet lag

Taking a long trip can occasionally feel like playing Russian Roulette with my body. Sometimes I recover quickly and barely seem to notice the time difference, and other times I'm exhausted for days.

No matter how long it lasts, jet lag is never fun, and researchers still haven't found a "cure" for the bothersome side-effect.

But they have uncovered a new piece of the puzzle about what causes jet lag — and it could help ease the pain of your next globe trot.

It turns out that our internal clocks are a bit laggy — they run a tad longer than 24 hours. That makes westward travel easier, since it involves simply adjusting to a slightly longer day. Traveling east, on the other hand, is much tougher for the body to handle. So what's the best way to help convince your internal time-keeper (local time: confused o'clock) to run on the same schedule as your external clock, or the local time at your destination? Sunlight.

To get a closer look at what's going on in our bodies when we travel, scientists recently experimented with the "master clock" cells, located deep inside the brain, that play a role in helping our bodies keep track of time.

What they found confirmed what several studies have suggested for years: molecules on these cells interact with other molecules throughout the body to keep our biological clocks running smoothly. Several genes (along with the proteins they make) also play a role in keeping these internal clocks ticking.

But how do these molecules know what time it is? They get information from our environment, including how light or dark our surroundings are. The lighter and brighter it is, the earlier it is; the darker it is, the later it is.

When we travel long distances, our bodies don't get the input they need to tell time. That confuses our internal clocks, which also tend to run a few minutes longer than 24 hours. Put these two factors together — no daylight cues + laggy internal clocks — and you've got a recipe for jet lag.

But it turns out that jet lag is much worse for one kind of trip: those that involve traveling east. Why? Because when we travel east, we have to set our (slow) internal clocks earlier and cut our days short. Conversely, when we travel west, we simply set them later and deal with a slightly longer day. Studies suggest that we can convince our internal clocks it's about two hours later each day but we can only convince them it's about 1 to 1.5 hours earlier each day.

While 30 minutes to an hour may not seem like much, it can have some pretty big effects if you're crossing multiple time zones. 

That's why the best way to address the problem and make your jet lag misery as brief as possible involves matching your biological clock to the local time of your destination as quickly as possible. One of the best ways to do this is to get lots of sunlight in your destination, which tells your body it's time to stay awake! "Natural light exposure is the ideal mechanism for counteracting jet lag," the authors of a 2011 study in the journal Pharmacy and Therapeutics write.

This can be tough to do when you get off a long flight mid-day and feel exhausted, but the effects will probably be worth it. If you're in a new place, try exploring by taking a walk outside. If your traveling for work, take your work where it's sunny. Your body will thank you.

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