Journal of Medical Sciences

Melatonin: A Powerful Hormone for Preventing Jet Lag


Preventing jet lag and industrial accidents caused by drowsy night workers are just two uses of a powerful hormone that can reset the body’s biological clock, researchers say.

The financial savings on industrial accidents alone could be significant. The nuclear accidents at Three Mile Island in the United States, Chernobyl in the Ukraine and the chemical leak at Bhopal, India, all occurred at night when human error is more likely, said researchers at a recent London conference.

The hormone is melatonin, produced by the pineal gland at the base of the brain, a gland named for its resemblance to a pine cone. Melatonin output is highest in darkness and sunlight suppresses its flow.

In some respects melatonin represents darkness, because it’s made at night,” said Josephine Arendt, Emeritus Professor of Endocrinology at the University of Surrey in Guildford, England.

In humans it has a property in shifting the so-called body clock, which is an internally generated, roughly 24-hour rhythm. It will advance or delay the cycle – shift it eastward or westward if you like, in the case of time-zone travelers.

Arendt has tested melatonin in long-term trials to treat jet lag on more than 400 people and in small studies on shift workers. In the larger study those taking the hormone were able to reduce their jet lag, with very few side-effects such as headaches or sleepiness. The shift workers slept better during the day and were more alert at work.

Arendt and others say the other promising treatment for shift workers is bright light, which was first used as a therapy for certain psychiatric illnesses, such as winter depression. It is now used in workplaces in the United States and essentially consists of increasing workplace illumination in the early morning hours.

Researchers say melatonin and bright light are complimentary treatments but the correct timing of the therapies is essential.

All of the disorders that have responded to the phase-shifting effects of appropriately timed exposure to bright light should also respond to appropriately timed melatonin administration,” said Alfred Lewy, a professor of psychiatry at the Oregon Health Sciences University, Portland.

Says Arendt, “Think of melatonin as darkness. You know that if you turn the lights out earlier in the evening you will go to sleep earlier. If you take melatonin in the late afternoon or early evening, this has a similar effect.

If you leave the lights off or put blinds on your bedroom until late in the morning then you will sleep later and get up later. Taking melatonin in the morning will induce this effect. Bright light works in the opposite way, so if you use it at the opposite end of the cycle you reinforce the effect.

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