All About Melatonin

Melatonin is a hormone that regulates your circadian rhythm, or the 24-hour cycle of biological processes called your "internal body clock." It helps oversee sleep, hormone production, cell repair, brain activity and other body functions.

The pineal gland in your brain makes most of the melatonin you need from the brain chemical serotonin. The gastrointestinal tract and other areas of the body also produce melatonin.

Commercially available melatonin is obtained from the pineal glands of cattle or is made synthetically. This form of melatonin is sold as an over-the-counter (OTC) or prescription sleep aid.

Small amounts of melatonin are also found in certain plant foods. Oats, sweet corn and rice have the most melatonin, followed by ginger, tomatoes, bananas and barley.

Light and dark

Your body's melatonin production is triggered by darkness and stopped by light. Melatonin levels in your blood increase in the evening and stay elevated through the night, reaching a peak between 2 and 4 a.m. Melatonin levels then fall and stay very low during the day.

Do melatonin sleep aids work?

Much research has been on done on melatonin, but there is little evidence that the hormone taken as a supplement can help with most sleep problems, including insomnia.

Melatonin supplements may be effective in certain circumstances. They can help a condition called delayed sleep phase syndrome. A person with this condition has difficulty falling asleep until very late at night, but then wakes early in the morning. In 2004, the Agency for Healthcare Research and Quality (AHRQ) concluded that melatonin supplements could be effective for this condition when taken for a short time: days or weeks. It did not recommend taking them for a longer period.

For some people, melatonin supplements may decrease the time it takes to fall asleep after going to bed. But the supplements do not appear to help improve sleep quality, or increase total sleep time or the amount of time spent in rapid eye movement (REM) sleep, the most important phase of sleep, the AHRQ says. The supplements also do not appear to help people with insomnia or jet lag.

Melatonin does appear to increase total sleep time for a type of insomnia caused by anxiety or other mood disorders, neurological conditions such as dementia and Parkinson's disease, or chronic pulmonary disease, the AHRQ says. For this type of insomnia, however, melatonin did not change the time it took to fall asleep.

In 2005, the Food and Drug Administration (FDA) approved a prescription drug, Ramelteon, to help people with insomnia fall asleep. Ramelteon is not melatonin, but another chemical that mimics the effect melatonin has on brain cells.

Side effects and other concerns

Short-term side effects of melatonin supplements tend to be mild. They include headache, insomnia, rash, upset stomach and nightmares. In addition, melatonin may interact with other OTC or prescribed drugs. More research is needed to understand the short and long-term effects of melatonin.

OTC melatonin supplements come in a variety of brands. It is important to recognize that these different brands may differ in dosage and/or ingredients.

Before taking an OTC melatonin supplement, discuss your sleep problem with your health care provider. Your provider can tell you the possible benefits and risks of taking melatonin.

Other melatonin research

Scientists believe that melatonin may play a role in a large number of conditions, but more research is needed to define its role as a cause or a cure. Despite extensive research, no definite recommendations exist for using melatonin in many medical conditions.

These are some current areas of research on the effects of melatonin:

• Seasonal affective disorder. When the days are shorter and darker, the production of melatonin increases. One theory about SAD is that the seasonal changes influencing the rise in melatonin control the course of SAD.

• Narcolepsy. This is a chronic neurological disorder characterized by excessive daytime sleepiness and a sudden loss of muscle tone caused by the brain's inability to regulate sleep-wake cycles. Melatonin may have a role in treating this disorder.

• Reproductive cycle. Melatonin may help regulate the reproductive cycle, especially the onset of puberty.

• Immunity. Depending on the amount and time of the dose, melatonin may either promote or suppress the immune system.

• Blood pressure. Melatonin increases the normal drop in blood pressure that occurs at night, thereby possibly protecting the heart from damage.

• Antioxidant properties. Antioxidants are substances such as vitamins A, C and E that inhibit reactions that could damage the body. Melatonin may help prevent damage or help the body heal after it is damaged.

• Skin diseases. Melatonin may help protect the skin against damage by the sun or even protect against certain skin diseases.

Melatonin may also play a role in the prevention or treatment of cancer. Several recent studies found that the risk for breast cancer was significantly higher among women who regularly work at night. One theory says that nighttime exposure to artificial light stimulates the growth of breast tumors by suppressing the levels of melatonin. Extended periods of nighttime darkness may slow the growth of these tumors. Melatonin's role in the treatment of prostate and colorectal cancers and leukemia is also being researched.