The Hormone Shortcut to Dreamland

The ancient Greeks believed that sleep was ruled by a god who dwelled deep down in the underworld. Surprisingly, they were wrong on this point.

Sleep, it seems, is at least partly under the influence of melatonin, the hormone produced by your pineal gland, located way up in your head.  Melatonin seems to work by influencing your circadian clock, or body clock, the internal timepiece that tells your body when it's day and when it's night. High levels of melatonin in your blood tell you it's sleep time. Low levels tell you it's wake time.

When everything's working as it should, your pineal gland produces melatonin when the light dims in the evening. And it stops production when daylight resumes, so melatonin levels nose-dive at dawn. Of course, everything doesn't always work as it should. If you stay up late with the lights on several nights in a row or fly through several time zones in the course of an evening, you can throw your circadian clock way out of sync. You may find that your melatonin levels rise and fall out of synchrony with your body clock's sleep/wake timing and that you are wide-awake in the dead-quiet dark of night.

This is where melatonin supplements can come in handy. In a number of studies, melatonin has been shown to help reset people's circadian clocks, says Andrew Monjan, Ph.D., chief of neurobiology of the Aging Branch of the National Institute on Aging in Bethesda, Maryland. It's helped insomniacs doze off and jet-setters avoid the sleeplessness and fatigue of jet lag.

If you're having trouble sleeping, though, better talk to your doctor before popping some melatonin. Insomnia may be a symptom that's caused by something specific—such as a side effect of medication, notes Quentin Regestein, M.D., a sleep disorders physician at Brigham and Women's Hospital in Boston. And melatonin supplements may not mix with other medications that you're taking. If these factors are taken into account, however, and your doctor recommends melatonin, you might give it a try, he says.

There's one caveat. The Food and Drug Administration doesn't regulate the manufacture of melatonin supplements. So it's hard to know what's in the stuff on the shelves. In one study, researchers examined the contents of various supplements and found "evidence of all sorts of substances that weren't accounted for" on the label, says Dr. Regestein.