Jet lag: why your body clock falls behind and what can ease it

That mid-afternoon urge to crawl into bed, or lying wide awake at 3am, is a familiar part of long-haul travel. Jet lag happens when local time changes abruptly and the body’s internal clock takes time to catch up. After crossing several time zones, your biological time initially stays aligned with home while you try to sleep, eat and function on destination time. The mismatch can lead to disturbed sleep, daytime sleepiness, poor concentration, irritability, reduced performance and digestive problems.

Nearly every cell in the body keeps its own 24-hour clock, synchronised by a master clock in the brain. Sunlight and darkness set that master clock, so a sudden shift in time zones means it takes days to adjust. Travelling east is often harder, because the average human cycle is slightly longer than 24 hours, making it easier to delay than advance your clock.

There is no cure, but steps can soften jet lag. Morning light sets your clock earlier, while evening light keeps you up later, so getting outside at the right time can help. Daytime walking and exercise reinforce the new schedule. Eating by day and avoiding food for several hours before bed helps, since late-night eating can delay melatonin release. Melatonin is a prescription drug in the UK and should only be used if prescribed, and supplements bought abroad may not match the stated dose. Bedtime routines matter too: keep lights low, and make the room dark and cool.