Melatonin is a hormoneproduced in the body and secreted at night. Taken as a dietary supplement, it is designed to help combat lack of sleep and may be useful for jet-lag. N-acetyl-5-methoxytryptamine, or melatonin, is hormone produced naturally by the body in the pineal gland of the brain. The release of melatonin correlates with the body's cycle of day and night. The highest levels of the hormone are produced at night. Trace amounts of melatonin appears in foods.