Does Melatonin Actually Help With Jet Lag?

This Cochrane review pooled ten randomised trials testing oral melatonin, taken at the destination's bedtime, against placebo in travellers crossing five or more time zones. Eight of the ten trials showed a significant reduction in jet lag symptoms. In two trials with detailed data, 67 percent of people taking a placebo reported significant jet lag, compared with only 17 percent of those taking melatonin, meaning roughly two people would need to take it for one to get meaningful relief. The benefit was more pronounced flying eastward and when crossing a greater number of time zones, and there appeared to be no advantage to taking it before departure rather than at the new bedtime.

This is now an older review, last substantively updated in 2003, and it draws on a modest pool of trials with real variation in dose and timing between them, so its size doesn't match the more rigorous meta-analyses common in newer sleep research. Melatonin quality and regulation also vary considerably between markets and products, something the review itself flags as a concern. Still, it remains one of the few systematic evaluations of a genuinely low-cost, low-risk intervention for jet lag, and its core finding, take it at the new local bedtime rather than before the flight, has held up in subsequent guidance.