People’s reactions to melatonin can vary

The Irish Times
Health Supplement, p. 13
3 June 2008

DOES IT WORK? Melatonin and insomnia

As summer holidays approach, plans of travelling to far-away places will be on the horizon. The excitement can be dampened by thoughts of jet lag. This differs from general travel tiredness because a good night’s sleep generally doesn’t overcome it. Jet lag is caused by our natural ‘body clock’ being thrown out of sequence by crossing time zones. On average, for every three time zones crossed, it takes two days for the body clock to adjust. During the adjustment, sleeping difficulties and problems with concentration and mood are common.

Our body clock impacts sleep-wake patterns, body temperature, mood and several hormones. Flying through time zones leaves these cycles out of sync with one another. Several factors influence the body’s rhythms, including exposure to light and dark, exercise, food and a hormone called melatonin. The body’s production of melatonin cycles during the day, influenced by light and darkness. This has led to much interest in melatonin as a treatment for jet lag. Melatonin is available in Ireland only by prescription, although it is classified elsewhere as a dietary supplement.

Evidence from studies

Melatonin levels are highest during the night and lowest during the day. Its levels start increasing around the time people start feeling sleepy. People who produce abnormally low levels of melatonin often have insomnia and melatonin has been used to successfully treat this condition. However, on average, people fell asleep only 10-15 minutes faster when taking melatonin compared to placebo.

Studies involving melatonin and jet lag have had conflicting results. A systematic review is a carefully structured way to summarise the results of several different studies. One published in 2003 concluded that melatonin provided some modest protection against jet lag, while one published in 2006 concluded that melatonin was ineffective. Some of the older studies were poorly designed and many were very small. A difficulty with this research is that people vary a lot in how and to what degree jet lag affects them and then how they respond to melatonin. Another problem studying any sleep aid is the power of the placebo effect. One study found that the quality of people’s sleep improved significantly after they were told they would receive melatonin, but before they actually received any melatonin.

Problematic aspects

Melatonin normally does not cause side effects. However, anyone with liver or kidney problems should not take it as these problems may allow its level to build up in the body. Taking any hormone orally can suppress the body’s normal production of that hormone. This may lead to sleep problems once the tablets are stopped. Some people experience drowsiness and dizziness after taking melatonin, which is usually worse with alcohol or other sleeping tablets. Do not drive within 4 or 5 hours of taking melatonin.


Different things help people adjust more quickly to new time zones. These depend on whether flying was to the east or the west, and how many time zones were passed through. In general, jet lag is negligible if fewer than three time zones were crossed. If staying three days or less, keep to your home schedule as closely as possible.

Sleeping during a flight should be limited to coincide with night-time at the destination. After flying to the west, direct sunlight should be avoided later in the day, while after flying east avoid early morning light. To stay alert in the new time zone, caffeine can be helpful, as can light exercise. Melatonin may be worth discussing with your doctor, especially if jet lag has been particularly problematic in the past. People respond best to up to 5 mg at the destination’s night-time on the day of arrival and for up to 5 days after arrival. People vary widely in how much melatonin helps them, but it may be worth trying. Products available elsewhere as dietary supplements may not be manufactured to the same quality as those available on prescription.

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