15/10/2025
Jet Lag – what works and what about melatonin?
Jet lag is caused by your body clocks being ‘out of sync’ when you land in another time zone. It can mess with your sleeping, and in some people, feeling out of sorts for a few days. Not everyone is bothered by jet lag, so the symptoms are not inevitable. The more time zones you travel across, the worse the jet lag feels – especially if you’re flying east. It’s really a function of air travel because of the speed of change, for most of human evolution travel was so slow that your body kept up with the changing day/night cycle.
Most cells in our body, if left to their own devices, have internal clocks including your body temperature – which is at its lowest at 4am. But the clocks throughout the body are told what to do by a central clock in the brain, which responds to day and night – namely the strength of light passing from the eyes to the brain. One result of this is that melatonin is produced from the pineal gland at night and helps to bring on sleep and that’s why people use it to treat jet lag. But as it turns out if melatonin works, it isn’t by taking it at night at your destination. More on that later.
The reason that flying west is easier on your body clocks is that the time shift is to later in the day. This fits better with the natural timing of our body clocks, which is longer than 24 hours in the absence of sunlight.
So, here’s what elite athletes are advised if they want to be in as peak condition as possible when they arrive. If flying west, they start the process about three or four days beforehand. They shift their bedtimes an hour later each night, try to get light exposure in the evening as well and darkness in the morning. If flying east, they shift bedtime an hour earlier each night, if they can, and avoid light in the evening and maximise exposure in the morning. Mealtimes are shifted in a similar way.
If you’re flying, get whatever sleep you can and try to avoid alcohol and large meals. At the destination, get exercise – because this does shift your body clock, and don’t be afraid of a short afternoon nap.
Now back to melatonin. This is your choice in consultation with your GP. The evidence is not terrific, since jet lag is so individualised and subjective. What seems to be the case is that taking melatonin at night can mess with your body clock adjustment. What some experts recommend instead, is to time your melatonin around your lowest body temperature (4am wherever you are). Flying west, they say you should take the melatonin four hours afterwards – so at about 8 or 9am and if flying east then about 11 or 12 hours before the minimum so around 3-4pm in the afternoon. 2mg doesn’t appear to work, and the advice is to take 5mg but no more. Vivid dreams are a side effect.
And for what it’s worth, I avoid alcohol on the flight, sleep when I can, then get out-and-about when I arrive. I also think it helps scheduling a flight which arrives at night so you can go straight to bed. I don’t take melatonin because I don’t like swallowing medications which haven’t been studied as well as I’d like.
Hope that helps when you’re lucky enough to have your next overseas trip!
by Dr Norman Swan | September 2025
