Jet lag myths debunked
Most popular jet lag advice doesn’t work because jet lag is a circadian clock problem, not a sleep problem. Sleeping pills, special diets, exercise, hydration and supplements don’t reset your clock. Correctly timed light exposure and light avoidance – supported by low-dose melatonin – are the only natural ways to reset it, and light at the wrong time can make jet lag worse.
Travelers are constantly bombarded with misguided, non-scientific advice from non-experts on how to alleviate jet lag, resulting in many misconceptions about the best way to tackle it. The problem is that, often, those providing the advice do not fully understand the underlying science and causes of jet lag. As a result, their advice is based on the wrong assumptions. This information is unwittingly passed on to the public by well-meaning but incorrect media articles, leaving people misinformed and confused about what to do.
Claims that their approach is tried and tested, used by executives or the military, or based on long-standing alternative medical practices try to lend an air of authenticity, but there is little evidence to support the claims when they are scrutinized. If a solution focuses on sleep as the problem – as many do – this is a red flag that the science of jet lag is not well understood. Only by resetting the internal circadian clock, using well-validated, tried, and tested methods, can jet lag be addressed. It’s time to replace the myths with science.
Understanding jet lag: The science behind circadian clocks
Most life on Earth is adapted to the daily 24-hour light/dark cycle caused by the rotation of our planet. We have a 24-hour circadian clock, located in the suprachiasmatic nucleus (SCN) in the brain, that helps us manage the regular rhythm of our day. Jet lag is caused when the sleep/wake and light/dark cycle shift too quickly for our circadian clock to keep up with.
How light affects your circadian clock and jet lag
Surprisingly to many, light is the most important time cue for resetting your circadian clock. Our internal, genetically determined clocks run, on average, a little longer than 24 hours – in fact, on a “day length” of about 24 hours and 12 minutes. This clock is reset each day by the 24-hour light-dark cycle to keep our internal rhythm in sync with the outside world. While 24.2 hours is the average, individual clocks range from ~23.5 to ~25.0 hours. This clock time determines your diurnal preference – whether you are an early bird (a morning type), a night owl (an evening type), or somewhere in between. Those with a shorter clock period tend to be more morning types, and those with a longer period, more evening types. This difference in internal clock time means that, to reset their clocks to 24 hours, different people need different light-dark exposure patterns day to day to properly synchronize.
When challenged with jet lag, it is even more important to time light and light avoidance correctly. Managing when to see light and when to avoid light is critical to adapting to new time zones quickly. The right light exposure at the right time can significantly accelerate your adaptation. Seeing light at the wrong time – as often recommended by non-experts – will make your jet lag worse.
The role of melatonin
In addition to timed light exposure, melatonin is also a “chronobiotic,” something that can shift your clock either earlier or later depending on the circadian time of administration. The right type and dose of melatonin, at the right time, can help you shift faster and sleep better as you transition between time zones. Taking it at the wrong time, or simply when you sleep, can make your jet lag worse. The timing of light and melatonin also needs to be properly aligned. If you take melatonin without timing your light exposure correctly, it will not be as effective, and you will not adapt to your new time zone any faster.
Jet lag myths you need to stop believing
Any jet lag “solution” that does not have light and light avoidance as the central planks of the advice will not help you adapt to new time zones faster. Some advice may aim at improving sleep or reducing sleepiness, but this does not address the underlying cause of jet lag – a little like treating a fever without addressing the underlying infection. This may seem to help in the short term but is not the most efficient or effective solution and may prolong your jet lag symptoms.
Given that appropriately timed light exposure and light avoidance are vital to alleviating jet lag, many of the common “tips” may alter your light exposure in the wrong way, making them ineffective or even worse.
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Myth 1 – “Sleep as much as possible on the plane”
Sleep equals dark as far as the circadian clock is concerned, so if you sleep at a time when you should be seeing light, you will shift your clock in the wrong direction and worsen jet lag. Advice focused only on sleep, without resetting the circadian clock, assumes that insomnia and sleepiness are the only symptoms of jet lag, which is not the case. A good example of this problem comes from the light-dark patterns provided on planes. Airlines often switch off the lights to encourage sleep or turn on the lights and wake you up at the wrong time, exacerbating your jet lag. Sleep (dark) and wake (light) timing should be scheduled as part of the overall light-dark exposure plan designed to reset the circadian clock as quickly as possible.
Myth 2 – “Use sleep medications to beat jet lag”
While sleep medications may help you sleep on the flight or in the hotel, they are less effective when trying to sleep at the wrong circadian time. Importantly, they don’t shift the circadian clock and could lead you to miss seeing light at the right time, or avoiding light when you should not, which is the real solution to jet lag. Sleeping medications are not necessary if light-dark exposure is timed properly to reset the clock. Once the clock is reset, you should be able to sleep at your normal time.
Myth 3 – “Fight jet lag with lots of caffeine”
While caffeine does not reset the circadian clock – although some companies wrongly claim it does – caffeine can be a useful tool to help manage jet lag and ensure that you stay awake at the right time to see light. The trick with caffeine is “little and often” to help maintain alertness at the right time, but stopping early enough to minimize the negative effects of caffeine on sleep. Caffeine stays in your circulation a long time – caffeine taken even early in the morning will affect your sleep that night. Many people think that caffeine does not affect them, but it does – they just don’t realize it! Only a small amount of caffeine is needed to achieve maximal alertness (a cup of tea or weak coffee, or about 40-50mg every ~2 hours). Be wary of advice recommending larger doses of caffeine.
Myth 4 – “Special diets or fasting adjust you quickly”
Many claims have been made about diets or fasting being able to reset the clock. These claims are based on studies of nocturnal (night-active) rodents, which cannot be translated to day-active humans. Food does not reset the clock in the brain, and there is currently no accepted method for using food – or fasting – for resetting circadian rhythms. Totally blind people, who cannot have their circadian clocks synchronized by light, are not entrained despite having very regular meal timing. While advice on what and when to eat may help avoid the metabolic consequences of jet lag caused by eating at the wrong biological time, it will not alleviate the underlying cause.
In addition to the circadian clock in our brain, we also have clocks in peripheral tissues and organs, such as the heart, liver, lungs, pancreas, and kidneys, which help us keep local time under the control of the circadian clock in the SCN – a little like individual players in an orchestra under the supervision of the conductor. Based on animal work, these clocks are likely to be more sensitive to food than the circadian clock in the brain, and meal timing could theoretically help reset them more quickly. As yet no one knows how to reset peripheral clocks in humans as the research is still ongoing. Advice claiming to know how to reset peripheral clocks in humans is not based on science.
Myth 5 – “Take dietary supplements for jet lag relief”
Dietary supplements such as Vitamin C, Vitamin B6 and B12, Omega-3 fatty acids, fish oil supplements, tryptophan, cherry powder extracts or juice, chocolate, chili, and magnesium have been claimed to help with jet lag, despite no evidence that they can reset the clock. They are also sometimes scheduled multiple times a day, which would confuse the circadian clock even if they were a chronobiotic. The circadian – 24-hour – clock needs time-cue signals once a day, scheduled according to a Phase Response Curve (a plot that describes the direction and magnitude of circadian resetting according to the time of administration) to be reset. Therefore, taking anything more than once per day cannot have a circadian effect, by definition.
There are no PRCs for any substance other than melatonin, so there is no way to know how to time any other supplement to reset the clock. Even if they did have a clock-resetting effect, without a PRC, their timing might shift the clock in the wrong direction and worsen jet lag. Supplements claimed to help with jet lag symptoms, without resetting the underlying clock disorder, are not addressing the cause of jet lag. See jet lag remedies compared.
Myth 6 – “Morning runs help reset your circadian clock”
Exercise is at best a very weak circadian synchronizer in humans: Its clock-shifting effects are extremely modest and require a substantial and sustained physical effort. The time at which you exercise may also lead you to see light at the wrong time and shift your clock in the wrong direction, worsening your jet lag. Exercise needs to be timed as part of the overall light-dark exposure plan.
Furthermore, while your circadian clock is still adapting to the new time zone, your 8am run may actually occur at a very different biological time, meaning you could be exercising in the middle of the night according to your circadian clock, when your temperature is low and your muscles are cold, increasing the risk of injury. You may also be very sleepy at this time if not fully adapted to the new time zone, further increasing your risk of a trip or fall.
Myth 7 – “Switch to the destination schedule immediately”
Many generic advice sites recommend setting your watch to the new time zone when you board the plane and trying to live on the destination schedule as quickly as possible. This is often bad advice and highlights a poor understanding of jet lag solutions. Maintaining your normal routine based on clock time, not circadian time, may lead you to see light at the wrong time and worsen jet lag.
For example, when traveling from the USA to Europe, you will need to avoid light in the mornings for the first few days to adapt quickly. Waking up and seeing light at 7am in Paris is equivalent to 1am in New York or 10pm in Los Angeles if your clock is not yet adapted. Light at that time will shift your clock later, the opposite of what you need to do for an eastward trip. Light needs to be timed according to your circadian clock, not clock time, using a science-based plan.
Myth 8 – “Blue-blocker glasses prevent jet lag”
Glasses that preferentially block blue light are claimed to block the alerting and clock-resetting responses to light when light exposure should be avoided. Some companies even claim that 99% of the effective light is blocked. This is not the case. While short-wavelength ‘blue’ light is the most effective part of the spectrum for resetting the clock and alerting the brain, other wavelengths of light, including violet and green light, also reset the clock, although less well. Blocking only blue light will only do part of the job – perhaps only 50% of the full effect – and will not prevent the other active wavelengths of light.
There is no need to buy expensive “blue-blockers”; your normal dark sunglasses that block all wavelengths will do the job just as well, and probably better. Whichever glasses you use, knowing how to time light avoidance is critical. Just like light exposure, light avoidance must be timed according to the Phase Response Curve for light. If you get it wrong, jet lag will be worse.
Myth 9 – “Airplane lighting helps with jet lag”
Colorful LED lighting on new airplanes looks great, and some airlines even claim to provide light that helps reduce jet lag. Unfortunately, these lighting systems nearly always deliver the wrong light at the wrong time, or the wrong intensity or spectrum of light. As described earlier, the lighting and meal schedules on most flights are not timed to help you reduce jet lag and, in fact, are often timed incorrectly, making your jet lag worse.
Myth 10 – “Flying business class improves sleep which reduces jet lag”
Many travelers choose to spend money on business class specifically to reduce the symptoms of jet lag, believing that sleeping on the flight will make them ready to work as soon as they land. The sleep and lighting schedules on flights are not personalized to address the underlying cause of jet lag, however, and often make it worse. Business class can be great, but you get the most out of it only if you know when to sleep and wake to ensure appropriate light-dark exposure, maximizing circadian resetting.
Myth 11 – “Staying hydrated cures jet lag”
Although drinking water and staying properly hydrated is important for your overall health and will make you feel better, it will not reset the circadian clock or alleviate jet lag.
Myth 12 – “Massages or acupressure fix jet lag”
None of these methods have been shown to reset the circadian clock and, therefore, cannot address the underlying cause of jet lag. While they may make you feel relaxed and improve your sense of well-being, they will not help you adapt to a new time zone more quickly.
Jet lag treatment
The challenge is to find the right timing for when to see and avoid light, take melatonin, sleep or nap, and use caffeine effectively. Solving this challenge is deceptively complicated, not intuitive, and can only be determined based on your sleep pattern, chronotype, itinerary, and personal constraints. With Timeshifter’s jet lag app, you can create personalized jet lag plans with all of this in mind. The app uses scientifically validated methods to help you reset your circadian clock and adapt to new time zones quickly and effectively. By following a science-based approach, you can overcome jet lag and make the most of your travels.
FAQ
Does sleeping on the plane cure jet lag?
No. As far as the circadian clock is concerned, sleep equals darkness, so sleeping when you should be seeing light shifts your clock in the wrong direction and can worsen jet lag. Jet lag is caused by a misaligned circadian clock, not simply lost sleep, so sleep and wake timing should be scheduled as part of an overall light-dark plan designed to reset the clock.
Do sleep medications beat jet lag?
No. Sleep medications may help you fall asleep, but they do not shift the circadian clock and can cause you to miss seeing light at the right time. Once the clock is reset through correctly timed light exposure, you should be able to sleep at your normal time without them.
Does caffeine reset the circadian clock?
No. Caffeine does not reset the circadian clock, despite some claims to the contrary. It can help you stay awake at the right time to see light, but it should be used little and often – roughly 40–50 mg every two hours – and stopped early enough to avoid disrupting sleep.
Do special diets or fasting reset your body clock?
No. Food does not reset the circadian clock in the brain, and there is no accepted method of using diet or fasting to reset human circadian rhythms. Such claims are largely based on studies of nocturnal rodents, which do not translate to day-active humans.
Do dietary supplements help with jet lag?
No. With the exception of melatonin, supplements such as vitamin C, B6, B12, omega-3s, tryptophan, or magnesium have not been shown to reset the circadian clock. Only melatonin has a known Phase Response Curve that allows its timing to be used for circadian resetting.
Do morning runs or exercise reset your circadian clock?
No. Exercise is a very weak circadian synchronizer, and a huge amount of exercise does very little to reset the clock. Poorly timed exercise can also lead you to see light at the wrong time, shifting your clock in the wrong direction and worsening jet lag.
Do blue-light blocking glasses prevent jet lag?
Only partially. Short-wavelength ‘blue’ light is the most effective part of the spectrum for resetting the clock and alerting the brain; violet and green light also work, but less well. Blocking blue light addresses only part of the effect. Ordinary dark sunglasses that block all wavelengths work as well or better, and the timing of light avoidance matters most.
Should you switch to the destination time zone as soon as you board?
Not necessarily. Living on destination clock time immediately can lead you to see light at the wrong circadian time and worsen jet lag. Light should be timed according to your circadian clock, not local clock time, using a science-based plan.
Does staying hydrated cure jet lag?
No. Drinking water and staying properly hydrated is important for overall health and may help you feel better, but it does not reset the circadian clock and will not alleviate jet lag.
What actually works for jet lag?
Correctly timed light exposure and light avoidance are the only natural ways to reset the circadian clock and adapt to a new time zone. The right type and dose of melatonin, taken at the right circadian time, can speed adaptation further. Sleep, caffeine, and meal timing all need to be coordinated with the light-dark plan rather than scheduled in isolation.
References
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- Czeisler CA, Duffy JF, Shanahan TL, Brown EN, Mitchell JF, Rimmer DW, et al. Stability, precision, and near-24-hour period of the human circadian pacemaker. Science, 1999; 284(5423): 2177–2181.
- Khalsa SBS, Jewett ME, Cajochen C, Czeisler CA. A phase response curve to single bright light pulses in human subjects. The Journal of Physiology, 2003; 549(Pt 3): 945–952.
- Lewy AJ, Ahmed S, Jackson JM, Sack RL. Melatonin shifts human circadian rhythms according to a phase-response curve. Chronobiology International, 1992; 9(5): 380–392.
- St Hilaire MA, Gooley JJ, Khalsa SB, Kronauer RE, Czeisler CA, Lockley SW. Human phase response curve to a 1 h pulse of bright white light. The Journal of Physiology, 2012; 590(13): 3035–3045.
- Wyatt JK, Cajochen C, Ritz-De Cecco A, Czeisler CA, Dijk DJ. Low-dose repeated caffeine administration for circadian-phase-dependent performance degradation during extended wakefulness. Sleep, 2004; 27(3): 374–381.
