Overcoming jet lag: what research and practice really recommend
Jet lag is more than tiredness — it is a circadian conflict between your internal clock and the new daily rhythm. Knowing how the body processes time differences lets you speed up the adjustment deliberately.
What jet lag means biologically
Jet lag arises from the shift of the circadian rhythm relative to the external day-night cycle at the destination. The internal clock continues to follow the departure location — and needs time to reset. Adjustment takes roughly one to one and a half days per time zone. For a flight from Europe to North America (six to nine hours' time difference), that can take nearly a week.
Sack (N Engl J Med, 2010) described the biology of jet lag precisely: the suprachiasmatic nucleus (SCN) in the hypothalamus — the master pacemaker of the internal clock — adapts to new light-dark cycles, but more slowly than travel demands. Direction matters: travelling westward (lengthening the day) is easier for most people than travelling eastward (shortening the day), because the biological clock naturally runs slightly longer than 24 hours.
Light: the most important tool
Light is the strongest time cue for the internal clock. Herxheimer and Petrie (Cochrane Database Syst Rev, 2002) showed in their meta-analysis that melatonin works for jet lag — but timing is key. Light is an even more effective lever because it acts directly on the SCN.
The basic rule: seek local daylight at your destination as quickly as possible. Morning daylight (within the first hours after waking) signals the new time to the brain. Those who have flown eastward should avoid afternoon daylight (it would push the clock further in the wrong direction); those who have flown westward can use evening light to aid adjustment.
Using melatonin correctly for jet lag
Melatonin is the only supplement with good evidence for jet lag. The Cochrane review by Herxheimer and Petrie found consistent effects: taking it at bedtime at your destination — for several days after arrival — helps the internal clock shift. The effective dose is 0.5 to 5 mg; lower doses are no less effective.
Eastman and Burgess (Sleep Med Clin, 2009) developed structured protocols for eastward and westward flights. The key message: melatonin works best in combination with light management — neither alone is as effective as both together. For short trips (fewer than three days), it may be more sensible to keep the home time zone rather than putting extra strain on the body through rapid adjustment attempts.
Sleep on the plane: what helps and what does not
Anyone wanting to catch up on sleep during a long eastward flight should try to stay awake for the first few hours (to avoid falling asleep too early relative to the departure timezone) and sleep in the second half of the flight. Sleep masks and earplugs are helpful. Alcohol on board measurably worsens sleep quality — the cabin air with its low humidity and reduced pressure already does that on its own.
Neck pillows and reclining seats improve sleep quality on the plane. If a business-class option is not available, you at least benefit from choosing a window seat (a fixed wall to lean against) and avoiding caffeine in the four to six hours before your target sleep time.
Preparation before the trip
Anyone who can invest a little extra time before a long-haul trip should start three to five days before departure, shifting sleep times gradually towards the destination — sleeping and waking earlier for eastward flights, later for westward ones. Even a shift of one hour per day reduces the adjustment effort at the destination.
Hydration is underestimated: aircraft cabins have very dry air (below 20 percent relative humidity). Drinking enough water keeps the body in better shape for sleep and recovery.
How the YUTHI app can help you
If you are planning a trip across a large time difference, you can log sleep times before and after the trip in the YUTHI app and compare them. This shows you how long your individual adjustment takes — and whether light management or melatonin measurably shortens the adaptation time. For frequent travellers, this builds into a useful personal protocol.
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