Hormone can reset one's body clock
By J. E. Brody - NY Times (9/28/95)

While researchers debate how far-reaching melatonin's benefits to the human body may be, no one argues about one function of the hormone: its ability to reset the body clock.

Research interest in melatonin began with the discoveries that light suppresses its secretion and that, like light, the hormone has a strong influence on a person's circadian rhythm, as scientists call the body clock, which influences when people are likely to fall asleep or wake up, among dozens of other internal rhythms.

Perhaps, scientists reasoned, just as light can shift the clock, melatonin might be used to help reset a clock out of sync with a person's surroundings.

This loss of synchronization can happen when people fly across time zones or when workers shift from working days, to nights, then to days. In addition, some people suffer from a sleep disorder resembling permanent jet lag; their body clocks keep them awake at bedtime and asleep in the morning when they are supposed to get up and start their day.

Distortions in the body clock are also a factor in winter depression, the condition called seasonally activated depressive disorder, or SADD. Winter depression is typically associated with a body clock that behaves as if it were earlier than the actual time; as a result, those suffering from winter depression often have trouble waking up in the morning during the months when dawn breaks late and dusk falls early.

How to use melatonin

Melatonin is a hormone produced by the light-sensitive pineal gland at the base of the brain. Melatonin is secreted only during darkness. Its secretion stops when the eyes are exposed to daylight or its artificial equivalent, an exposure that can occur even when the eyes are closed.

The trick in properly using melatonin to reset the body clock, a step called phase shifting, is to take the hormone at the right time and in the right amount to adjust the clock without causing sleepiness at the wrong time. Unfortunately, both the melatonin dosages commonly sold and the instructions on how to use the hormone are inappropriate for adjusting a person's circadian rhythm.

Dr. Alfred Lewy, an expert on circadian rhythms at the Oregon Health Sciences University in Portland, said that it takes only tiny amounts of melatonin, much less than a milligram, to reset the body clock.

The higher doses, from two milligrams to tens of milligrams, that are now widely sold over the counter will reset the clock, but usually cause sleepiness, which is not what most people want upon arriving in Paris in the morning or when starting a night shift.