How Jet Lag Affects Your Body

Planning a long-distance trip that crosses multiple time zones? You may already be dreading the fatigue, sleeplessness, and irritability that come with adjusting your body’s internal clock. Jet lag, or desynchronosis, can lead to insomnia, daytime drowsiness, poor focus, fatigue, irritability, disorientation, depression, and digestive issues [source: Eastman and Burgess]. A 1998 study revealed that 94% of Americans flying long distances suffer from jet lag, with 45% of them experiencing severe symptoms [source: James].

While jet lag is uncomfortable, it’s not just a nuisance. The Pentagon is concerned that jet lag could impact pilots' performance and put soldiers at risk, while businesses worry that jet-lagged executives may make poor decisions in meetings. A 2010 study by University of California researchers found that hamsters exposed to chronic jet lag produced new neurons at half the normal rate compared to sedentary hamsters, leading to memory and learning difficulties [source: Sanders].

There is growing evidence that jet lag may be detrimental to your health, especially as you age. A 2006 study from the University of Virginia discovered that older mice subjected to weekly flights equivalent to a Washington-to-Paris trip showed an increased death rate, whereas younger mice recovered from the effects of air travel [source: Wilber]. Other research suggests that jet lag could exacerbate menstrual issues and contribute to heart disease and diabetes by disrupting eating habits [source: Eastman and Burgess].

What can a fatigued traveler do to overcome the challenges of jet lag? Over time, people have tried a range of methods, from running to using caffeine to stave off sleepiness, to exploring herbal and dietary supplement solutions. While a one-size-fits-all remedy for jet lag is still out of reach, experts in health say there are plenty of strategies to help your body adapt to the shift in time zones and feel your best wherever you land. But first, let’s explore the causes of jet lag and why it can leave us feeling miserable.

What Causes Jet Lag?

Our bodies contain clusters of interacting molecules within cells, acting as internal clocks, regulating the release of hormones and controlling other variables like body temperature. Much like how timepieces around the world rely on the Royal Observatory in Greenwich, UK, the body's internal clocks synchronize with a central timekeeper: the 20,000 nerve cells of the suprachiasmatic nucleus (SCN) located in the hypothalamus region of the brain [source: NIH].

The SCN governs our body's circadian rhythm, a regular cycle of sleep-wake patterns and other bodily functions. For example, when it's time to sleep, the SCN signals the release of melatonin, which makes us sleepy. The SCN knows when to trigger this response because it's located near the optic nerves that transmit light perception from the eyes to the brain. When light decreases, the SCN sends the signal to release more melatonin, helping us fall asleep. However, the body thrives on regularity, and this internal clock is accustomed to following a consistent pattern each night [source: NIH].

However, the body’s natural timekeeping system struggles to adjust rapidly, and when crossing multiple time zones, it can cause significant disorientation. This problem is most pronounced when flying eastward, such as traveling from Chicago to Paris. Even though it's nighttime at your destination, your body still believes it’s the late afternoon. You may find yourself wide awake in your hotel room all night, only to drift off just as it's time to rise for morning croissants and coffee [source: Eastman and Burgess].

When you're sleep-deprived, it throws almost every bodily function out of balance. Stress hormones surge, making you feel irritable and tense. Your blood pressure increases, and inflammatory chemicals rush through your veins. The disruption also affects the hormones that control your appetite, leading to strong urges to binge eat at times when you usually wouldn't feel hungry. Additionally, your body’s natural melatonin production, which not only helps you sleep but also regulates other hormones and defends you from illnesses like cancer, gets thrown off balance [source: Stein].

Why Jet Lag is So Difficult to Overcome

Re-setting your body’s internal clock is far more challenging than just remembering which buttons to press on your Timex Ironman. The human circadian rhythm, on average, runs just slightly longer than 24 hours, which means most people naturally tend to fall behind schedule every day. This could explain why our bodies adapt more easily to a phase delay (east to west flights) than to a phase advance (west to east flights), which requires going to bed earlier. Research showed that it took participants four days to adjust to a 12-hour phase delay, while those adjusting to a 12-hour phase advance still couldn’t fall asleep normally after eight days [source: Eastman and Burgess].

Another factor to consider is that sleep isn’t only impacted by light. Your body temperature also varies while you sleep, reaching its lowest point ("Tmin" in sleep science jargon) around three hours before you typically wake up. Jet lag symptoms are often most intense when you’re forced to wake up during your body’s Tmin. This explains why you might feel groggy and mentally foggy, even if it seems like you’ve had a full night’s rest [source: Eastman and Burgess].

Over the years, travelers have tried all sorts of methods to deal with jet lag. Some people opt to tough it out, pushing through sleepless nights and long days until it's time to crash at bedtime, even though this can be tough on both your body and your mind. Others rely on herbal remedies or melatonin supplements to ease the symptoms. A few adventurous souls even take overnight flights, hoping to sleep in their seats with the aid of sleeping pills. However, doctors strongly warn against this approach. The human body simply isn't built to sleep deeply while sitting, and staying in one position for extended periods can increase the risk of blood clots, or thrombosis. A case published by The New England Journal of Medicine highlighted a healthy 36-year-old woman who, after sleeping in her seat for seven hours, tragically suffered a fatal stroke [source: Schneider].

But don’t worry. In the next section, we’ll share expert advice from medical and travel professionals on safer and more effective ways to manage jet lag.

What the Experts Recommend

If you're hoping for a quick fix, like a pill that solves jet lag, we're afraid you'll be disappointed because such a solution doesn’t exist—yet. However, there’s a strategy proposed in a 2009 article by biological rhythms researchers Charmane I. Eastman and Helen J. Burgess from Rush University Medical Center in Chicago. They recommend adjusting your rhythms ahead of time before traveling by using a light box that simulates sunlight. For a west-to-east trip, go to bed one hour earlier for several nights before departure, waking up earlier and using the light box to simulate daylight. For an east-to-west trip, stay up later for several nights before your flight, using the light box at your usual bedtime to stay alert. When you wake up, avoid bright light for a few hours, and if you must go outside, wear dark glasses [source: Eastman and Burgess].

Eastman and Burgess also suggest trying melatonin, a supplement that isn’t FDA approved but has been shown to help shift circadian rhythms in studies. To manage a west-to-east phase advance, take 0.5 mg about four and a half hours before bed, gradually shifting the dose earlier as you adjust to going to sleep earlier. For an east-to-west journey, reverse this process [source: Eastman and Burgess].

If that feels too intricate for you, you might prefer the simpler suggestions from the U.S. Centers for Disease Control and Prevention (CDC) to ease circadian issues. The CDC recommends maintaining a regular exercise routine, eating a well-balanced diet, and ensuring adequate rest in the weeks leading up to your trip, believing that a healthy lifestyle will help you recover more quickly from the stresses of travel.

While flying, the CDC advises avoiding alcohol and caffeine, as both can negatively impact sleep, and drinking plenty of water. They also recommend wearing loose, comfortable clothing and moving around the cabin when possible. Lastly, the CDC suggests not stressing over jet lag. If you can, adjust your schedule to avoid critical meetings or important decisions until you've had a couple of days to regain mental clarity [source: Yanni].