Melatonin is a hormone produced in the pineal gland which is located within the brain. The hormone is principally made at night when light is absent and is essential in regulating the body’s internal clock (called circadian rhythm) and the deep stages of sleep. Melatonin increases sleepiness, reduces the time it takes to fall asleep, reduces the number of nighttime awakenings, and reverses daytime fatigue. The amount of melatonin produced during the night is ten times the amount produced during the day and nighttime levels remain elevated for about 12 hours. With aging, the pineal gland produces less melatonin and this decreased production accelerates after age 40. One cause of disrupted sleeping with aging is this reduction of nightly melatonin release.

Melatonin regulates many processes besides sleep. It is one of the most potent antioxidants in nature, helping to protect the body from degeneration due to free radical damage (free radical damage can lead to cancer). Melatonin also decreases susceptibility to stress, strengthens the immune system, helps with jet lag and improves mood. Low melatonin levels have been linked to hypertension and reduced immunity.