Melatonin

What is it?

Melatonin is a natural hormone that regulates the human biological clock.

Double-blind research with young adults has shown that melatonin facilitates sleep.¹ Another study of healthy, young adults reported that melatonin significantly shortened the time needed to go to sleep, reduced the number of night awakenings, and improved sleep quality.² Other researchers reported the time needed to get to sleep was reduced with melatonin.³

Melatonin is also helpful in relieving symptoms of jet lag. One double-blind trial, involving a sample of international flight crew members taking either melatonin or a placebo for three days before and five days after an international flight, found that melatonin significantly reduced symptoms of jet lag and resulted in a quicker recovery of preflight energy levels and alertness.⁴

Less than 1 mg of melatonin has lowered pressure within the eyes of healthy people,⁵ but studies have not yet been published on the effects of using melatonin with people who have glaucoma.

Melatonin might help some people suffering from depression. A small double-blind study suggested that supplementation with small amounts of melatonin (0.125 mg taken twice per day) may reduce winter depression.⁶ People with major depressive disorders sometimes have sleep disturbances. Melatonin has been shown to be effective at improving the quality of sleep of people with major depression.⁷ However, because of the possibility that melatonin could exacerbate depression, it should only be used for this purpose, under a doctor’s supervision.

When some people take melatonin to treat sleep disorders, chronic tension headaches are relieved.⁸ Melatonin has also relieved cluster headaches in double-blind research.⁹ Some researchers have suggested that melatonin’s role in regulating core body temperature may be responsible for preventing cluster headaches,¹⁰ which have been reported to be triggered by increased body heat.¹¹

Melatonin also regulates immunity. One group of doctors reported two successfully treated cases of sarcoidosis that it attributed to melatonin’s immune-modulating effect.¹² Also, because of its effects on the immune system, melatonin has been given to people with cancer in many research trials. Low blood levels of melatonin are associated with an increased risk of uterine cancer.¹³ Melatonin has significantly reduced the level of prostate specific antigen (PSA, a marker for cancer) in prostate cancer patients.¹⁴ Melatonin inhibits breast cancer cells in test tubes¹⁵ and has put some women with breast cancer into remission in preliminary research.¹⁶ Melatonin supplementation has improved disease-free survival in people with melanoma¹⁷ and increased survival in people with brain cancer¹⁸ and lung cancer.¹⁹ Melatonin exerts anti-inflammatory activity that may be responsible for its anticancer properties.²⁰

In a double-blind trial, people who had difficulty sleeping as a result of tinnitus were better able to sleep if given 3 mg melatonin per night for one month rather than a placebo.²¹ Although melatonin did not reduce overall symptom scores for tinnitus, people in this trial with higher symptom scores did appear to obtain some benefit.

Melatonin supplementation may be helpful in treating epilepsy; 5–10 mg of melatonin taken at bedtime reduced the frequency of seizures and improved sleep in a group of children with epilepsy in a small, preliminary trial.²² However, in a group of children suffering from neurological disorders, 1–5 mg of melatonin per night led to an increase in the rate of seizures.²³ Children with a seizure disorder called "myoclonus" were reported to have been cured by supplementing with 3–5 mg of melatonin per day in a preliminary trial.²⁴ Until more is known, children with neurological conditions should take melatonin only under medical supervision.

Melatonin may be useful in the treatment of fibromyalgia. In a small, uncontrolled preliminary study, 3 mg of melatonin at bedtime was found to reduce tender points associated with this disorder. Pain and fatigue improved only slightly.²⁵

Children with Angelman’s syndrome (a rare, genetic disorder characterised by severe mental retardation, seizures, and sleep disturbances) may benefit from low amounts of melatonin. In an uncontrolled study, children with Angelman’s Syndrome who took 0.3 mg of melatonin one-half to one hour before bedtime had significant improvement in night-time sleep patterns and a reduction in movement disturbances during sleep.²⁶

Animal studies indicate that melatonin secretion may regulate cardiovascular activity,²⁷ ²⁸ blood pressure,²⁹ and blood flow to the brain.³⁰ In healthy young men, oral administration of 1 mg of melatonin significantly reduced blood pressure and levels of stress hormones within 90 minutes.³¹ To date, no clinical trials in humans have tested the efficacy of melatonin for hypertension.

Where is it found?

Melatonin is produced by the pineal gland, located within the brain. Levels of melatonin in the body fluctuate with the cycles of night and day. The highest melatonin levels are found at night. Melatonin is present in foods only in trace amounts.

Melatonin has been used in connection with the following conditions (refer to the individual health concern for complete information):

Science Ratings

Health Concerns

Angelman’s syndrome (sleep disturbances only)

Irritable bowel syndrome (for abdominal pain only)

Jet lag

Schizophrenia (for sleep disturbances only)

Sunburn

Tardive dyskinesia

Tinnitus (insomnia-associated)

Age-related cognitive decline

Myoclonus

Sarcoidosis

Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars

Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star

For a herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.

Who is likely to be deficient?

Although elderly people often have difficulty sleeping³² and melatonin supplements have been shown to improve sleep in the elderly,³³ melatonin secretion does not appear to decline in healthy older adults to a significant degree, despite many preliminary reports to the contrary.³⁴ Most of these preliminary studies failed to verify that older subjects were healthy and not using drugs that suppress melatonin secretion (e.g., aspirin, ibuprofen, beta-blockers). Routine replacement of melatonin in elderly persons is, therefore, not recommended.

Adults with insomnia have been shown to have lower melatonin levels.³⁵ Frequent travelers and shift workers are also likely to benefit from melatonin for the resynchronization of their sleep schedules,³⁶ though a melatonin “deficiency” as such does not exist for these people. Patients with heart disease have been reported to have low melatonin levels, but whether this abnormality increases the risk of heart disease or whether heart disease leads to the low melatonin level is not yet known.³⁷ People with schizophrenia were found to have low melatonin output and experienced significantly improved sleep following melatonin replacement supplementation.³⁸

How much is usually taken?

Normally, the body secretes melatonin for several hours per night—an effect best duplicated with time-release supplements. Studies using timed-release melatonin for insomnia have reported good results.³⁹ Many doctors suggest 1–3 mg of melatonin taken one to two hours before bedtime. Studies with people suffering from sarcoidosis or cancer have used very high amounts of melatonin—typically 20 mg per night. Such levels should never be taken without the supervision of a doctor. Melatonin should not be taken during the day.

Are there any side effects or interactions?

Melatonin is associated with few side effects. However, morning grogginess, undesired drowsiness, sleepwalking, and disorientation have been reported. Researchers have hypothesized that certain people should not use melatonin supplements, including pregnant or breast-feeding women, people with depression or schizophrenia, and those with auto-immune disease, including lupus, at least until more is known.⁴⁰ ⁴¹

In one study, administration of 3 mg per day of melatonin for three months resulted in a marked decline in sperm counts and a decline in sperm quality in two of eight healthy young men.⁴² In one of these two men, sperm count and quality became normal after melatonin was discontinued. Although this was a small study, it raises the possibility that long-term use of melatonin could lead to infertility.

In a group of children suffering from neurological disorders, 1–5 mg of melatonin per night led to an increase in the rate of seizures despite the fact that sleep improved.⁴³ Until more is known, children with neurological conditions should take melatonin only under medical supervision.

Many other side effects have been attributed to melatonin supplementation, including inhibition of sex drive, severe headaches, abdominal cramps, and formation of rudimentary breasts in men.⁴⁴ ⁴⁵ However, these associations have not been supported by solid evidence.⁴⁶ ⁴⁷ ⁴⁸ ⁴⁹ Since none of these claims have been well documented or independently confirmed, these problems may not have been due to melatonin.

Though most research reports that melatonin improves the quality of sleep, at least one trial has found that four of fifteen men given melatonin had their sleep patterns disturbed by supplemental melatonin.⁵⁰

One case of painful gynecomastia (enlarged breasts) has been reported involving a 56-year-old man who had been suffering from amyotrophic lateral sclerosis (Lou Gehrig’s disease), and was taking 1–2 mg melatonin per day for one and a half years.⁵¹ As the signs and symptoms disappeared after melatonin was discontinued, the authors of the report suspected that melatonin caused this side effect.

According to a preliminary report, blood levels of melatonin may be elevated in women with fibromyalgia.⁵² Data in this report did not indicate toxicity from melatonin, nor did the report suggest that melatonin causes or exacerbates the symptoms of fibromyalgia. It did suggest there is no current rationale for melatonin supplementation in people with fibromyalgia.

One-time oral administration of 1 mg of melatonin to post-menopausal women reduced glucose tolerance and insulin sensitivity when tested 45 minutes after administration.⁵³ This finding suggests that people with diabetes should use melatonin with caution and only under the supervision of a doctor.

Are there any drug interactions?
Certain medicines may interact with melatonin. Refer to drug interactions for a list of those medicines.

Special United Kingdom considerations

Melatonin is either not available or may require a prescription. People should check with their physicians.

References
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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or chemist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires March 2007.