March 2, 2005 - As dietary supplements go, melatonin was a superstar just a decade ago. Books and newsmagazines celebrated the hormone as a cure for sleep ills, aging, and even cancer. But the scientific evidence to back up the hype never materialized.
These days, the supplement is largely promoted as a natural way to get a good night's sleep. But does it work?
A large review of studies, published late last year, found melatonin to be safe when taken for short periods but not particularly effective for people with long-term sleep problems. Now a newly published review of selected research shows the hormone to be modestly effective in treating insomnia.
Sleep medicine specialist Frank Scheer, PhD, of Boston's Brigham and Women's Hospital has studied melatonin for several years. He says the jury is still out on the supplement's effectiveness for promoting nighttime sleep in people with long-term sleep problems.
Are Benefits Overstated?
I think it is fair to conclude that melatonin is not the miracle sleep aid that it was once believed to be," he tells WebMD. "Its benefits for sleep have been largely overstated."
In a review of 130 studies, published in December 2004, researchers reported that taking melatonin appears at best to be mildly beneficial in the treatment of insomnia and other ongoing sleep disorders. The report also found little evidence of a benefit for jet lag.
But the review did indicate that people with a specific sleep condition known as sleep phase syndrome can benefit from taking the hormone for limited periods. People with this condition have a hard time both falling asleep at night and waking in the morning.
The newly published report included 17 studies involving 284 people with and without insomnia. The studies varied in things such as the amount and quality of the melatonin taken by the participants.
Researchers concluded that taking melatonin reduced the time it took people to fall asleep by an average of 4 minutes. Total sleep time per night was increased by about 13 minutes.
"The general conclusion was drawn that melatonin has only a modest sleep-promoting effect, with an increase in sleep efficiency of 2% to 3%," Scheer wrote in an editorial accompanying the analysis. Both were published in the February issue of the journal Sleep Medicine Reviews.
Daytime Sleep, Jet Lag
Scheer tells WebMD that while the benefits of taking melatonin for nighttime sleep are unproven, the hormonal supplement does appear to help shift workers and other people who need to sleep during daylight hours.
Melatonin is produced naturally by the brain's pineal gland at night to regulate sleep, but production goes way down during the day. Melatonin supplementation appears to trick the body into thinking that it is nighttime.
While the large review suggested that melatonin is not useful for jet lag, Scheer says that may only be half true. He says the supplement may help speed up the internal clock, helping to adjust to a new time zone. But it does not seem to be as effective in helping to readjust to one's original time zone.
So while taking melatonin may benefit a traveler who loses five hours flying from Boston to London, it probably won't help as much on the return trip.
"You would want to delay the onset of sleep when returning from London to Boston, and it appears that melatonin is not as effective for that," Scheer says.
Is Dosage the Key?
While the studies to date suggest that melatonin is only modestly effective for promoting nighttime sleep, all agree that the research is far from conclusive.
Massachusetts Institute of Technology neuroscientist Richard Wurtman, MD, is credited with discovering the sleep-inducing properties of supplemental melatonin back in the early 1980s. Wurtman served as principal investigator of the newly published review.
He tells WebMD that the research on melatonin and sleep is misleading because the dosages used in the studies were often too high.
Wurtman contends that the optimal dosage of melatonin is just 0.3 mg and that taking much higher doses causes the hormone to stop working within a few days. Commercially available melatonin preparations contain up to 10 mg of the hormone.
"People are getting doses of melatonin that raise [blood levels] of the hormone to up to 500 times what is normal," he says. "At that dosage it either stops working after a while or actually causes insomnia in some people."
He says supplement manufacturers market higher-than-optimal doses of melatonin because MIT holds a patent on the hormone at dosages of up to 1 mg. That patent was issued before the FDA classified melatonin as an unregulated dietary supplement.
"If the FDA were regulating melatonin as a drug, as I believe it should be, then it would be sold in its highest fully effective dose, which is 0.3 mg," Wurtman says. "But that isn't happening."
Wurtman's research suggests that melatonin is both safe and effective for the long-term treatment of insomnia and other sleep problems when taken at this dosage shortly before bedtime. He says this appears to be especially true for elderly people.
Because MIT and Wurtman stand to benefit financially if melatonin is marketed at dosages of 1 mg or less, the neuroscientist says he understands that some people will question his motives.
"People may not trust my work because they know I have this association," he says. "The only response I have is to put it all out there and be as forthcoming as possible."