Is melatonin a miracle drug or a myth? This is what I set out to find
out after several patients of mine mentioned that they were taking melatonin.
At the onset of my endeavor I must admit I thought that melatonin is
probably another one of the numerous "miracle drugs" that
ultimately do nothing more than separate one from his or her money.
When I was in medical school, melatonin was a mystery hormone secreted
by an obscure gland called the pineal gland. At that time, the function
of melatonin was a total enigma. Now we know much more about the pineal
gland and the amazing hormone it secretes. Melatonin is a hormone that
is secreted by a small gland in the center of the brain called the pineal
gland. At birth there is very little melatonin secreted by this gland.
It is not present until about 3 months of age. At that time, the nighttime
peak of melatonin increases dramatically and reaches its peak at about
2 to 3 years of age. Then, it gradually decreases with age. Melatonin
has been shown to promote sleep. Elderly people do seem to have a difficult
time sleeping and it is hypothesized that this is because of the decreased
secretion of melatonin. The melatonin level in the blood decreases rapidly
as we wake and are exposed to sunlight in the morning. The melatonin
level peaks in the middle of the night.
The Antioxidant Effect
Antioxidants are compounds that metabolize dangerous molecules in our body called free radicals. Free radicals can attack cellular membranes and even damage our DNA. Some commonly used antioxidants are Vitamin E, Beta-carotene and Vitamin C. Melatonin has been shown, at least in the lab, to be much more potent than any of these well-known antioxidants. Everyone has naturally occurring compounds that neutralize free radicals. Dr. Reiter and his colleagues have shown that small doses of melatonin can prevent rats from contracting cancer when exposed to certain cancer-causing compounds. One such compound is safrole. This compound can cause the production of free radicals that oxidize DNA, thus altering its structure. Damaged DNA can promote the development of cancer. When rats received melatonin in combination with safrole there was almost no damage to the DNA. Melatonin also prevents chemically induced cataracts in rats. Cataracts are formed by free radicals that cause damage to the cells in the lens of the eye. Free radical damage is probably involved in the etiology of many diseases such as Parkinson's disease, multiple sclerosis, Alzheimer's disease, atherosclerosis and many more. Whether or not treatment with melatonin will be beneficial remains to be seen.
Immune Function and Melatonin
Research has demonstrated that melatonin has the ability to enhance or augment the function of the immune system. It seems to be capable of neutralizing the negative effects that stress, drugs and infections have on the function of the immune system. Studies have demonstrated a stimulatory effect of melatonin on acquired immunity. Melatonin has been reported to increase natural killer cell activity.
The Anti-aging Effect
This is the most tantalizing assertion that some researchers have made about the benefits of melatonin. The claims are based on a prominent theory of aging that suggests that the anatomical and functional degeneration that organs undergo during aging is a consequence of accumulated free radical damage. If this theory is true, it would follow that prevention of oxidative damage by free radicals would promote longevity. Obviously, this would be hard to prove in humans since the life span is so long. On the other hand, rats have a much shorter life span and they don't object to being test subjects, so much research has been performed on them. Rats that are given daily doses of melatonin actually live 25% longer. Another study showed that when the pineal gland of an infant rat is grafted in the body of an old rat, a similar improvement in life span was observed. The older rats became more active and physiologically younger. It was hypothesized that an increased production of melatonin is the cause of the improved longevity.
Fortunately, there have been no significant adverse reactions from taking melatonin reported in the literature as far as I can tell. Doses of melatonin that are sold in health food stores are much higher than the doses ordinarily used in most studies in humans. Dr. Richard Wurtman of MIT's Clinical Research Center is doing studies on humans using melatonin to induce sleep. He feels that a more appropriate dose would be in the 0.5 mg. range. Dr. Wurtman has urged caution in using the health food store brand of melatonin.
A Word of Caution
Health food stores market melatonin as a dietary supplement and therefore it is not subject to the U.S. Food and Drug Administration regulations. The regulation of the dietary supplement market place is despicable to say the least. This category of compounds would include herbs. For the most part the claims made about these products are totally unsupported by legitimate medical research. Much of the time these companies do not have any medical research supporting their products. They do not have to show that their products have any definite positive effects. The products are not manufactured according to any set standards. The manufacturers can make almost any claims they want as long as they word their claims carefully. The purity of the products is totally unregulated, meaning you may get a different concentration of a supplement from one bottle to the next or from one manufacturer to the next. A real-life example of problems related to the "health-food" market place is exemplified by L-tryptophan. It was marketed for insomnia several years ago. It caused a condition called the eosinophilia-myalgia syndrome that resulted in 38 deaths and over 1500 reported cases. It was caused by contamination of the product which is a direct result of the lack of regulation.
Melatonin does seem to have some potential. I certainly don't think it would hurt to take melatonin on an occasional basis to try to prevent jet lag. On the other hand, I think we need to use caution in taking melatonin until more studies show a definite benefit in humans. The shelves of pharmacies are packed with numerous medicines that have theoretical properties that can improve health and longevity. Unfortunately, they rarely prove to be of any help and occasionally are harmful. For instance, vitamin E and beta-carotene have both been proven to not be helpful and possibly be harmful.
1. Reiter RJ, et al. A review of the evidence supporting melatonin's
role as an antioxidant. J Pineal Res 1995 Jan; 18(1):1-11
The information provided above is offered as a community service about
health-care issues and is not a substitute for individual consultation.
Advice on individual problems should be obtained from your personal
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