Commonly referred to as the sleep hormone, melatonin is a natural substance used by the body to endogenously regulate sleep and circadian rhythm. The pineal gland instinctively produces more melatonin in the dark to induce sleepiness while scaling back during the daytime to maintain alertness. This hormone plays a central part in regulating bodily rhythms. When taken externally, melatonin can realign the body with the outside world to assist with jet lag and improve sleep quality.*