Melatonin is a hormone secreted naturally by the pineal gland in the brain. Given its importance in promoting sleep, melatonin supplements have demonstrated consistent positive effects on subjective and objective measures of sleep quality.
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What is it and how does it help regulate sleep
Melatonin is a hormone secreted naturally by the pineal gland in the brain. Its main function is to coordinate circadian rhythms across multiple biological systems. It does this by responding to changes in ambient light to differentiate between night and day.
Briefly, light is detected by specialized cells in the retina that signal to the suprachiasmatic nucleus (SCN) in the brain. The suprachiasmatic nucleus is considered the body’s endogenous clock and master regulator of circadian rhythms1. During the day, the suprachiasmatic nucleus suppresses melatonin secretion by the pineal gland2. Release of inhibition at night increases melatonin production and promotes sleep. Melatonin also synchronizes other circadian rhythms, such as core body temperature, cortisol levels, blood pressure, and cellular metabolism3.
Given its importance in promoting sleep, melatonin supplements have been investigated extensively for use in insomnia. Many large meta-analyses collectively involving thousands of patients have demonstrated consistent positive effects on subjective and objective measures of sleep quality.
These include decreased sleep onset latency (time to falling asleep) as well as increased total sleep time and sleep efficiency (proportion of time spent asleep while in bed)4,5,6,7.
Melatonin supplementation had the most pronounced effects on individuals with sleep phase delay insomnia, which is characterized by an inability to fall asleep until late in the evening and, consequently, difficulty arising in the morning8. This phenomenon is consistent with melatonin’s known role in promoting sleep onset and suggests melatonin may be most useful for individuals who predominantly have difficulty falling asleep.
Key advantages to melatonin therapy include its accessibility as an over-the-counter agent, benign side effect profile, and absence of associated habituation or abuse potential.