Miracle or mayhem? A lot depends on the dose, but there's little medical evidence to support the outrageous claims being made for its powers in humans.
Is melatonin really the wonder drug it's cracked up to be? Publicity surrounding the hormone's so called benefits has been widespread, especially in the US and Canada where melatonin fever has taken hold. Melatonin pills, capsules and lozenges are leaping off store shelves.
Melatonin (not to be confused with melanin, which is skin pigment) supposedly slows the process of aging, and coordinates the hormones involved in fertility. It may also increase resistance to cancer and even act as a non-addictive sleeping agent to counteract the effects of jet lag, a modern malady from flying quickly across several time zones (BMJ, 1986; 292:1170). It's especially useful after eastward travel, which has been shown to seriously disrupt sleep patterns and increase anxiety and depression (Mol Cell Endocrinol, 1991; 79: C53-C58 and Int J Biometeriol, 1991; 35: 169-175).
In humans, melatonin is secreted by the pineal gland, a small, pea sized structure at the base of the brain which responds to the amount of light hitting our eyes. Discovered in the late 1950s, but recognized as a hormone only a few years ago, melatonin occurs naturally and keeps us in sync with the rhythms of the day. In fact, it's the chemical embodiment of night dusk or darkness triggers its production, helping us fall asleep, and sunlight inhibits it.
Various commentators describe its primary role as the regulator of the body's internal clock. There's strong evidence that melatonin works as a bedtime sleep inducer for some insomniacs. Like animals, the human body's level of melatonin decreases the older we get (J Pineal Res, 1986; 3: 379-388 and J Clin Endocrin Metab, 1982; 551: 27-29).
Melatonin supplements are therefore thought to be beneficial for the elderly (Lancet, 1995; 346: 541-4). A study conducted at the Technion Israel Institute in Haifa and other Israeli facilities by I Haimov, which examined melatonin levels in older people with insomnia (BMJ, 1994; 309: 167) found that quality of sleep in the elderly was proportional to the amount of melatonin secreted by the pineal gland.
Blind people are also affected by insomnia because they can lose track of the day's natural rhythm. Blindness afflicts more than a million Americans, a tenth of whom have no conscious perception of light. They therefore find melatonin levels decrease and they can't sleep, so supplements may be beneficial (Lancet, Dec 2, 1995), although boosting melatonin production by simply covering their eyes from bright daylight may also be effective as a way of maintaining a sleep pattern. When the peak of the melatonin rhythm corresponds to the time when blind patients have chosen to sleep, they sleep well and feel well (New Eng J of Med, Jan 5, 1995).
It may be useful in the treatment of Alzheimer's disease whose sufferers have lower melatonin levels (J Neural Trans [Suppl], 1978; 13: 289-310 and Med Hypoth, 1990;31:233-242); and osteoporosis (Int J of Neuro, February 1992).
Those suffering from cirrhosis of the liver don't make melatonin at the right time, so they tend to wake more during the night and take naps during the day (Annals of Int Med, August 15, 1995). And victims of coronary heart disease also have a problem with melatonin production. Levels have been shown to be much lower at night (Lancet, June 3, 1995).
Some also speak of "a tight physiological link" between the pineal gland and the immune system. Although vitamins A, C and E are well known fighters of oxidizing free radicals unstable molecules that oxidize healthy ones by pirating electrons from them they work only in certain parts of certain cells. Melatonin is considered a much more powerful anti-oxidant because it is thought to readily permeate any cell in any part of the body. Scientists say that oxidizing molecules play a major role in diseases such as AIDS, rheumatoid arthritis and cancer. Melatonin may well protect tissues against the onslaught of such diseases, helping to fight infection, but so far, research has only been carried out on animals.
Melatonin also dampens the release of estrogen, prolonged exposure to which supposedly increases the risk of breast cancer (Br J of Cancer, April, 1995).
Perhaps the most encouraging work is being done with patients who have inoperable cancers such as lung or liver cancer who are given melatonin and interleukin-2 (IL-2), a substance which helps the immune system fight foreign invaders. Melatonin appears to amplify the antitumour effect of IL-2. In one study of patients with untreatable spreading tumours, nearly half the patients given the metatonin mix were alive a year later, compared to only 8 out of 48 of those given support alone (Supp Care Cancer, May 1995). Similar results have been achieved in patients with brain tumours given melatonin alone (Cancer, February 1, 1994), as well as those with gastric cancer (Tumori, December 31, 1993) and lung cancer (Onc, 1992; 49 (5): 336-9).
But don't take everything at face value. Melatonin has a darker side you may not be aware of, particularly for healthy patients. Because it's sold as a dietary supplement rather than a medicine, this makes it exempt from US Food and Drug Administration (FDA) regulations which would otherwise scrutinize all melatonin products to make sure they are safe to take. Melatonin is therefore widely available uncontrolled from health food stores and pharmacies across the US.
The FDA says it hasn't received any reports of adverse reactions to melatonin. Nevertheless, it cautions : "This fact does not provide any evidence of safety, however, because it is very difficult to attribute illnesses or injuries to products of this type; and physicians often do not take medical histories in a way that would elicit such information."
Britain's Medicine Control Agency, run by the Department of Health, is preventing the open sale of melatonin until clinical tests demonstrate its safety, although it can be prescribed by GPs only (not naturopaths) "on a known patients basis only" that is, by prescription according to an MCA spokesman. This is because it is a hormone and, as such, is believed to exert a pronounced pharmacological activity on the body.
Melatonin is also banned from over the counter sale in Canada until a year's testing has been carried out on its effects, but it's being imported illegally from the US and stocked only on shelves because demand is so strong. Indeed, far from being worried about the concern over the drug's safety, by Health Canada, the federal agency that regulates food and drugs, there was an uproar when consumers found out about the ban. Although they can bring melatonin back from the US for personal use (no more than a 60 tablet bottle), many are dragging it in by the caseload (Maclean's, Dec 18, 1995).
Amid such fever, it's not surprising then that many have overlooked the absence of clinical test data to suggest melatonin is safe. So, at the moment, there's no way we can be sure how "pure" melatonin products are. We just don't know what's in them.
For example, in the last few weeks it has emerged that there are two kinds of synthetic melatonin being sold on the open market. Most brands are produced from soya milk, according to NutriCentre's director, Rohan Mehta. However, one product is made from melatonin plus a small amount of pineal gland produced from animals that is, cow's brains, supposedly supplied from the Far East. This of course raises the spectre of mad cow disease, a potentially life threatening condition passed on from cows to humans through offal. Nevertheless, Mehta says that this particular variety is not widely available.
Keen to use melatonin as a weapon against their existing malignancies, cancer sufferers may feel they have nothing to lose from taking melatonin because it improves their quality of life (Supp Care in Cancer, May 1995; 33: 194-7). But for otherwise healthy consumers buying melatonin over the counter, it's clearly a different story.
And there's no guarantee that consumers are taking appropriate dosages of the drug, either. Experts say that effective doses for these applications are usually less than 0.5 mg, far below the 2 mg to 3 mg doses commonly sold in stores. But we're all different and we don't know what effect different dosages have on our bodies long term.
Recent studies looking at melatonin's effect on jet lag show mixed results according to dosage and when it's taken (Bio Psych, April 1, 1993; 33 7: 526-30). In this study of flight crew, those who began taking melatonin before embarking on their flight were worse off than those who took a sugar pill. The best effects were among those who took a small amount (5 mg two days after they'd arrived for five days) after their flight.
Even though melatonin does help improve the quality of sleep, its effects on the way we perform need to be carefully monitored as well (Chronobiol Int, Oct 1993). For instance, among night workers, those taking melatonin were more alert during night shifts, but their memory and perception of their mental load were adversely affected.
Melatonin products may also carry a risk to patients with AIDS and other groups especially vulnerable to adverse drug interactions and infections. Richard Wurtman, Director of MIT's Clinical Research Centre, says that doctors should also be careful about prescribing melatonin to pregnant women, patients with psychiatric disease and anyone taking drugs that act on the brain. "Physicians who prescribe it now are really taking a risk," he says, "and they should do so with their eyes open."
Certainly melatonin enjoys a delicate relationship with the body's sex hormones. In fact, among healthy women, high doses may adversely affect the reproductive system. Studies have shown that melatonin increases the level prolactin and lowers the level of Follicle Stimulating Hormone (FSH) the hormone which prompts the ovaries to release their eggs each month (Melanoma Research, Nov-Dec, 1991). If you lower FSH, you may become infertile.
The facts are also being overshadowed by the melatonin hype being promulgated by those with a vested interest in its success. A book quite typical of the publicity surrounding melatonin The Melatonin Miracle, Nature's Age Reversing, Disease Fighting, Sex Enhancing Hormone and credited with fuelling the hype, bases claims on the authors' own published research carried out on laboratory mice, which did appear to live longer, healthier lives when melatonin was added to their drinking water.
The authors Walter Pierpaoli, an Italian researcher, and William Regelson, of the Medical College of Virginia, Richmond also cite data from other researchers' work with animals, but there is a very limited amount of evidence of tests carried out on humans.
And it should also be noted that MIT's Wurtman, perhaps the most prominent melatonin researcher around who has suggested low dosages as an alternative to the much higher levels recommended by existing products, holds stock in a company (Interneuron Pharmaceutical) he has co-founded that's developed a low dosage prescription preparation a melatonin based sleeping pill (America Medical News, Nov 6, 1995) and is applying to patent it.
However, there's something in what Wurtman says. His 1994 study of young adults carried out at MIT had 20 men of college age taking melatonin or a placebo an hour before lying down for a midday nap. Although it took Wurtman's placebo group about 25 minutes to fall asleep, those on the melatonin were out inside six minutes. According to Wurtman, melatonin acted as a mild sedative, even though the prescribed dose was 0.1 mg, less than the body itself circulates at night.
Russel Reiter, researcher and neuroendocrinologist at The University of Texas in San Antonio, (and author of yet another book on the subject) says more than 100 studies of the hormone's effect on humans have been carried out. In some cases, he claims, people took as much as 6,000 mg for up to a month and complaints were "minor" headaches, nausea and chronic grogginess (Total Health, August 1995).
But there's no telling what effects taking a hormone supplement sold over the counter unregulated and unpredictable will have on our bodies long term. Will it, for example, suppress the body's natural production of the hormone? Dr Ellen Grant, author of Sexual Chemistry, and hormones expert seems to think so. To Dr Grant, the melatonin hype is just the latest episode in a long line: "It has never been a good idea to introduce any hormone into the body," she says. "Outside hormones tend to suppress your own production. It's all a big nonsense."
But, in a few years' time, the melatonin market will be a multi-million dollar business, perhaps running into the billions, as millions of people flock to buy it. After all, it's cheap and readily available a month's supply in the US costs around $10 in health food stores.
The jury is still out. In the meantime, the hype surrounding melatonin and its effects is clearly spiralling out of control and is lining publishers' pockets. We advise caution.