Melatonin is a hormone produced by a wide variety of organisms. In humans, it is mainly produced by the pineal gland, a tiny organ in the brain of humans and most other vertebrates (animals with backbones). Melatonin is also found in smaller amounts in other parts of the body. Melatonin also occurs in extremely small amounts in some foods. In humans, melatonin promotes sleepiness. Darkness stimulates the body to produce melatonin. Light blocks the production of melatonin. The hormone helps regulate the circadian rhythm, the body’s natural cycle of waking and sleeping.
Melatonin is made from serotonin, an important neurotransmitter in the brain. Neurotransmitters are chemicals that carry impulses from one nerve cell to another. The body makes serotonin from an amino acid called tryptophan. Amino acids are organic acids that make up proteins and other compounds in living things.
Researchers have found that melatonin supplements may help people suffering from jet lag. Jet lag is a travel-related condition in which the natural sleep cycle and other biological functions become disrupted after crossing multiple time zones. Other research shows melatonin can help people who have trouble falling asleep.
Dietary supplements of melatonin range in dose from 0.5 milligram to 50 milligrams per tablet. Medical experts agree that the short-term use of melatonin at low dosages is safe, although it may cause drowsiness. However, researchers have not determined whether long-term use at higher dosages is safe, particularly in children and in pregnant or nursing women. People should consult a physician or a registered dietitian before taking any dietary supplement.
Scientists are studying many other possible effects of melatonin. For example, it is a powerful antioxidant. Antioxidants block the effects of oxidation, a chemical reaction in which a substance loses electrons. Antioxidants protect cells from the effects of free radicals, unstable molecules produced by oxidation. Scientists believe free radicals may be involved in a number of diseases. Scientists are investigating whether melatonin can help prevent or treat many diseases. These diseases include amyotrophic lateral sclerosis (ALS), Alzheimer’s disease, diabetes, Huntington’s disease, and Parkinson disease. The United States Food and Drug Administration (FDA) forbids manufacturers from claiming that any dietary supplement can treat, cure, or prevent disease.
