Melatonin - is it a cure for jet lag? When should you take it?
Cure jet lag: unlikely
Help with sleeping: unlikely, except when taken in a specially formulated slow release form as prescribed by a doctor in countries where it has been approved.
Help staying awake/alert: no help
Researchers have discovered that melatonin levels vary in sync with the body's daily clock (circadian rhythm). Since it is linked to sleep, it is typically low during the day, rising through the evening and night. There are many people who believe that taking melatonin may help shift the circadian rhythm into a new time zone and thereby overcome jet lag.
The evidence for using typical melatonin tablets to help beat jet lag ranges from some possible impact to a more general consensus that it has little effect. If melatonin levels are low during the day and peak late at night, why doesn't taking the drug have a measureable impact?
The major problem seems to be getting the timing and dosing right (see below: when to take melatonin). The drug is quickly absorbed, but is in the body for a relatively small amount of time. Studies suggest once taken in tablet form and absorbed, its levels drop by half every 30-120minutes - depending on the individual. However in a normal day, the body typically sees slow rising levels starting at 8pm for four hours and peaking around midnight for 4-5 hours at a sustained level before declining by 7am. This is roughly a cycle of 11-12 hours. This slow build to a sustained yet consistently high level is very difficult to mimic with tablets. To overcome this issues, there is a special form of tablet available that has a prolonged dosage. However, it is mostly available to individuals with more developed sleeping disorders and requires a consultation and prescription.
On the other hand, taking a single tablet creates a short peak and may not allow your body time to respond as it would during a normal daily cycle and that peak may be too short-lived to have an impact.
Also be aware that melatonin has some drug interactions with medication. In particular if you have epilepsy or are taking blood thinning medication. In general it can also cause nausea, irritability and grogginess the following day.
When to take melatonin
If you do decide to try melatonin and have talked to a trained health practitioner about the implications, the best strategy is to take it around 8pm local time on the first day of travel according to the dosage listed on the bottle or as advised by a medical practitioner, then for a following few nights thereafter. This is for east to west travel only. Mis-timing the dosage or using it for west to east travel may aggravate jet lag symptoms.