Maybe you’re jetting off to the coast, or to a sunny locale. Maybe you find yourself on business trips from time to time or even all the time. Whatever the reason, if you go far enough away from home, jet lag happens. Feeling tired after a serious time-zone change is a real thing. You don’t want to waste precious vacation time or productivity by feeling out of it for several days, nor do you want to feel like a zombie when you return home. While it’s probably inevitable that you’ll feel a bit tired while adjusting to a time-zone change, there are ways to mitigate the effects.
What causes jet lag?
Jet lag occurs when there is a sudden change in the alignment of environmental time cues, notably sunlight, relative to the body’s internal timing, which is also referred to as the circadian rhythm. So flying across time zones tends to have a similar effect as working the afternoon or night shift. Both situations cause the individual and his or her environment to be out of sync.
The reason jet lag causes negative effects is that the body has more than one circadian rhythm. Instead, every cell keeps its own internal time. Local networks of cells (tissues) allow pretty good coordination within organs. For example, even though individual liver cells keep time internally, most liver cells align to each other so that you can think of “liver time” as a thing. However, time is much less well-coordinated across different organs.
Your eyes are windows to the brain
Cells in your eyes have their own individual clocks which run on their own eye time and are sensitive to light. And these are particular culprits in jet lag, because they are the key communicator of light cues to your brain since your brain doesn’t get any light exposure itself. So while your eyes are communicating directly to your brain about light, they’re not communicating to the clocks in your liver, bones, etc. Those organs and tissues tend to rely on other cues, strongly influenced by metabolic cues, like when you eat, go for a run, etc.
Further complicating the jet lag equation is that your eyes and brain, because they are more affected by light, generally adjust within a day to your new setting. However, your other organs and tissues can only catch up to the new time at the rate of about an hour a day. And they adjust even more slowly if they get conflicting information about time, which happens if your eating and exercise habits don’t align with the light in your new environment. What these different rates of adjustment mean is that while you get used to a new time, the clocks in your body fall out of their normal alignment. As long as the normal alignment of organ times is disrupted, your organs will be doing things when other organs aren’t ready for them – like your stomach making acid when you’re not actually about to eat, giving you ulcers or acid reflux.
When your body clocks are out of sync
The misalignment of body clocks, which doctors and scientists call internal desynchrony, is what makes us feel bad when we have jet lag. As long as our body systems don’t line up, it is normal for us to feel unwell. It’s the body’s way of telling us that something is not right. Again, we can expect to feel that way about one day per hour of time zone change, given how long it takes our organs to move into alignment. It may take even longer if you’re traveling to an area that’s a much higher altitude than where you currently are.
So what can you do to minimize jet lag’s negative effects?
Get a head start on adjusting to the new time
To some extent, you can get ahead of your trip by adjusting your timing at home. Go to bed a little earlier or later, maybe shift your eating, waking, and sleeping schedules an hour toward the time zone to which you’ll be traveling. Sports teams are beginning to do this more. They are training at the time of day that will be local time for the event so that when the athletes fly and play the same day, their bodies are expecting to play at the right (internal) time. For example, athletes in New York might practice at 7 pm if they plan to fly to California for a 4 pm game in a few days.
Get all your timing cues aligned
Sleep, exercise, and eat on local times so that your body gets the same time information to all organs, no matter what cues they’re sensitive to. Getting bright light in the day is also important, just like making sure it’s dark when you sleep. Going outside helps with the former, and using a sleep mask can help with the latter, especially if you don’t quite sleep on local time the first day or two. Earplugs can also be beneficial.
Give yourself a break
Internal desynchrony disrupts your body as well as your ability to think and act. For the first 24 hours, you’re likely to be a bit under the weather, no matter what you do. So build in a day to relax when you arrive. Taking it easy for a day allows your body to focus on realigning itself and recovering, which is hard to do if you put additional stress on it by going gung-ho when you first arrive. Chilling out poolside isn’t lazy; it’s a smart move and an investment for the following days.
Accept that which you cannot control
We do not know of any superhumans outside of the movies. A normal human being is going to feel fatigued for a few days when traveling across time zones. So be aware, follow these tips, and make the most out of your trip.
Dr. Benjamin Smarr studies the temporal structures that biological systems make as they move through time. An NIH research fellow at UC Berkeley, his work focuses on understanding how physiological dynamics like sleep, circadian rhythms, and ovulatory cycles are shaped by the brain, and how disturbances to those cycles give rise to disease. Dr. Smarr is also an advocate for scientific outreach, and routinely gives public lectures and visits K-12 classrooms to help promote the idea that by understanding the biology that guides us, we can live more empowered lives.