Low-Dose Melatonin 

"Less Is More" When it Comes to Melatonin - For Sleep, and Perhaps Even for Sex

Too much of a good thing can be wonderful. - Mae West

Although sleeping (of sorts), as well as certain hormones, might have been on her mind, we can be pretty sure that Miss West wasn't referring to melatonin - the "sleep hormone" - when she made her classic remark. Melatonin is a hormone whose secretion by the pineal gland in the human brain is associated with our natural sleep-wake cycle. During the day, our melatonin levels are very low. At night, however, they rise dramatically, apparently in response to the fading light. Darkness is known to stimulate melatonin production, and it is believed that this is nature's biochemical signal for us to go to sleep.

Exactly how and why all this occurs is something of a mystery, especially when we realize that, although melatonin is found in most vertebrates, many of them are nocturnal, hunting by night and sleeping by day. So the melatonin effect as we know it is certainly not universal. In any case, we humans have it, and we have been trying for some time not only to understand it better but also to exploit it for our benefit, especially in cases of insomnia and jet lag. Both of these can occur at any age, but old age typically brings with it a marked increase in insomnia. Not coincidentally, it seems, melatonin production declines sharply in old age, often "drying up" almost entirely.

It is natural, therefore, to look to melatonin supplementation as a possible aid in sleeping, and there has been much research on this subject. (One new study on the effect of light levels on melatonin production is reported here.) In some of the studies, however, the amounts of melatonin given were much higher than those produced naturally by our bodies during the night. Although there is little reason to believe that such amounts are harmful in the short run, the long-term effects of sustained high doses of melatonin are unknown. Prudence suggests that anything as intrinsically powerful as hormones should be taken in amounts that are consistent with normal physiological levels.

That kind of concern is what prompted a study, conducted at MIT, to determine whether short-term behavioral effects, including the induction of sleep, could be induced by small daytime doses of melatonin that significantly elevate the serum melatonin levels while keeping them within the normal nocturnal range.1 If this were the case, it would suggest a similar role for the normal nocturnal increase in melatonin levels.

Some of the effects of that increase are to reduce core body temperature, to alter thermoregulation, to modify brain levels of monoamine neurotransmitters, to stimulate secretion of prolactin (a pituitary hormone that stimulates and maintains the secretion of milk), and, as we already know, to induce sleep. It is also possible that the nocturnal increase acts as a time signal affecting the temporal characteristics of other circadian rhythms (daily biological activity patterns that follow a 24-hour cycle).

To see how the diurnal (daytime) administration of melatonin might induce such effects, the MIT researchers recruited 20 healthy young men, aged 18-24, who were not prone to depression or seasonal affective disorder. All of them participated in five 8-hour testing sessions (from 9:30 A.M. to 5:30 P.M.), with at least five days between successive sessions. The study was double-blind and placebo-controlled. The test group received capsules containing 0.1, 0.3, 1.0, or 10 mg of melatonin at 11:45 A.M. on each of the five test days, while the control group received placebo.

Throughout each session, oral temperature was recorded hourly, and blood samples were taken at regular intervals for analysis of melatonin levels. Except for a half-hour lunch break (11:00 to 11:30), the occasional quick bathroom break, and a half-hour sleep period (1:30 to 2:00), the men were required to sit at a computer terminal with eyes open, performing a variety of assigned tasks designed to assess their alertness and mental acuity. They also had to answer "mood questionnaires" pertaining to their state of mind and sleepiness level at 10:30 and again at noon and every hour thereafter.

During the half-hour sleep period, the men were asked to lie down and relax in a quiet, darkened room, with eyes closed, while holding special electrical pressure switches designed to register the exact moment when they fell asleep. The idea was to see whether sleep-onset latency (the time interval from ingestion of the melatonin or placebo to the onset of sleep) would be decreased in the test group, i.e., whether the test subjects would fall asleep more quickly than those in the control group (they did, by an average of 10 minutes). After 30 minutes, the subjects were awakened, if necessary, and asked to get up and resume the test protocol.

The results of this study were summarized by the authors as follows: ". . . the 0.1- and 0.3-mg doses generated peak serum melatonin levels that were within the normal range of nocturnal melatonin levels in untreated people. All melatonin doses tested significantly increased sleep duration, as well as self-reported sleepiness and fatigue, relative to placebo. Moreover, all of the doses significantly decreased sleep-onset latency, oral temperature, and the number of correct responses on the Wilkinson auditory vigilance task. These data indicate that orally administered melatonin can be a highly potent hypnotic agent; . . ."

In a subsequent study, several of the same authors reported that oral administration of low doses of melatonin (0.3 and 1.0 mg) at 6, 8, or 9 P.M. (i.e., close to the time period when natural melatonin levels normally begin to rise) also decreased sleep-onset latency.2 The authors concluded that "These data provide new evidence that nocturnal melatonin secretion may be involved in physiologic sleep onset and that exogenous melatonin may be useful in treating insomnia." (Exogenous means "from outside the body.")

Lest we think that inducing sleep is all that melatonin is good for, consider its effects on sexual activity in rats. It is known that large doses of melatonin inhibit sexual behavior in male rats. But in yet another example of the "less is more" phenomenon, it has been found that small doses of this hormone (10 to 100 micrograms per kilogram of body weight) stimulate sexual activity in normal male rats. [The equivalent doses for an 80-kg (176-lb) man would be 0.8 to 8.0 mg.]

A new study done in Italy has shown that these small doses of melatonin cause sexually active male rats to initiate copulation with receptive females more quickly and more frequently than normal.3 Furthermore, the same authors have shown that these same doses of melatonin actually restore potency to impotent rats.4 Whether these results have any bearing on humans is unknown, but this is surely one of those times when we wouldn't mind too much being likened to rats.

If you have problems with sleep, don't count sheep (or even rats). Much more effective help than that is available for getting to sleep and staying asleep. The best place to start is with the article which appeared in the September 1999 issue of Life Enhancement.There you will learn more about the sleep-inducing qualities of melatonin as well as of 5-HTP, choline, and valerian root extract.

When you do sleep tight, may your sleep be restful and your dreams sweet, as in the Brahms Lullaby . . . .


  1. Dollins AB, Zhdanova IV, Wurtman RJ, Lynch HJ, Deng MH. Effect of inducing nocturnal serum melatonin concentrations in daytime on sleep, mood, body temperature, and performance. Proc Nat Acad Sci USA 1994 March;91:1824-28.
  2. Zhdanova IV, Wurtman RJ, Lynch HJ, Ives JR, Dollins AB, Morabito C, Matheson JK, Schomer DL. Sleep-inducing effects of low doses of melatonin ingested in the evening. Clin Pharmacol Ther 1995 May;57(5):552-8.
  3. Drago F, Busa L, Benelli A, Bertolini A. Acute low doses of melatonin stimulate rat sex behavior: the role of serotonin neurotransmission. Eur J Pharmacol 1999 Nov 26;385(1):1-6.
  4. Drago F, Busa L. Acute low doses of melatonin restore full sexual activity in impotent male rats. Brain Res 2000 Sep 29;878(1-2):98-104.