Originally Published: September 6, 1996 - Last Updated / Reviewed On: April 8, 2011
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Dear Alice,

Are there any benefits to melatonin, and are there known negative side-effects?

Dear Reader,

Melatonin is a hormone produced by the pineal gland in the brain that has a quick acting, sleep-inducing effect. It is a light-sensitive hormone, meaning that the absence of light stimulates its secretion. Melatonin may play a role in controlling the circadian rhythm, the body's internal clock and sleep cycle. Before puberty, the pineal gland produces comparatively large amounts of melatonin. As we age, melatonin production continually decreases, perhaps explaining why older people either have difficulty sleeping, or sleep less.

The melatonin most often found in health food stores and pharmacies is actually a synthetic version of the hormone; you can also purchase a form that combines synthetic and natural (from sheep pineal glands) melatonin. Both types of melatonin in a bottle mimic the real thing in chemical composition and behavior. However, more people favor the entirely synthetic form because it does not carry the risk of contamination that the partially organic form does.

People who occasionally have trouble sleeping or adjusting to time changes when traveling might benefit most from taking melatonin supplements. While there is no official recommended dose for melatonin, research suggests that keeping the dose close to what our bodies normally produce (<0.3 mg per day) is most effective. People respond differently to melatonin — some are more sensitive than others. If you decide to supplement with melatonin, it's best to start with a very low dose. Too high of a dose could lead to anxiety. Large doses of melatonin to children under 15 could cause seizures.

Few side effects of melatonin use have been reported. The most common are daytime drowsiness, headaches, and unusual dreams. At higher doses (up to 300 mg), volunteers in one study reported diarrhea, abdominal pain, and headaches. Current research proposes that melatonin is safe to use if you are: (1) over 18 years old and healthy, (2) not pregnant or breast-feeding, and (3) not taking any medications besides minor analgesics (e.g., aspirin, acetaminophen, ibuprofen) and oral contraceptives. Talk with your health care provider about taking melatonin if you don't fit the above description, or if you have a serious illness, an autoimmune disorder, diabetes or another endocrine disorder, or depression.

Many claims have been made to melatonin's miraculous powers, declaring that it can improve health in such diverse ways as boosting the immune system, fighting the effects of aging, curing cancer, and providing a safer means of birth control. Don't expect to cash in on all of these health benefits by taking melatonin just yet. While some of the preliminary research is quite promising and supports these claims, bear in mind that most of the research is still at the test tube and animal stages. It's a big jump from test tubes to humans; we may not see the same results from tests on real people. And, several researchers have pointed out that a handful of these studies were flawed in their methods, thus invalidating claims based on that research. At any rate, it will be a number of years before we really know what melatonin can and cannot do for our health.

We also won't know the impact of long-term melatonin use for at least a decade. What we do know is that hormones are powerful substances that can produce unexpected results. Because so many unknowns exist, we need to exercise caution in purchasing and taking melatonin. As a "dietary supplement," the U.S. Food and Drug Administration (FDA) does not have jurisdiction over the production, use, and sale of melatonin. So, we can't be absolutely sure of the purity or potency of what we are buying. One research project, which tested a sampling of melatonin, found that what the label stated the tablets contained, and what was actually in the tablets, often differed — some had more, or less, melatonin than they said; some had none at all, but regular sleeping medication instead. This isn't to alarm you as much as to emphasize the need for you to buy a reputable brand. Ask your health care provider or pharmacist to recommend a brand(s), and also suggest an appropriate dose for you.