These supplements contain natural or synthetic versions of melatonin, a hormone that our bodies produce to regulate the sleep cycle. “Melatonin is a hormone that’s naturally produced in the brain in response to darkness and helps to regulate the circadian rhythm and tells the body that it’s time to sleep, hence its nickname, ‘the hormone of darkness,'” explains Nishi Bhopal, M.D., a psychiatrist specializing in sleep medicine.
Bonney notes that the average person’s melatonin levels will start to rise after sunset and peak around 2am – 4am. If, for some reason, you are trying to fall asleep outside of your peak melatonin window (say, if you’re traveling to a new time zone or working during daylight hours), taking supplemental melatonin tells your body that it’s time for bed, despite what your environmental cues are saying.
“For adults, melatonin works by changing the timing of our 24-hr circadian rhythm. This is helpful if we are shift workers, our circadian rhythm is out of time with our regular work or school hours, or we wish to minimize travel fatigue,” says Michael Gradisar, Ph.D., a clinical psychologist and sleep specialist with Sleep Cycle.