Melatonin Function & Timing
topic
Melatonin is a hormone secreted by the pineal gland in response to darkness — signaling to the body that nighttime has arrived and initiating the physiological preparation for sleep including core body temperature drop, reduced alertness, and slowing of metabolic processes — without directly inducing sleep itself. Its secretion begins approximately 2 hours before habitual sleep time (the dim-light melatonin onset, DLMO) and is suppressed by even moderate light exposure, particularly in the blue spectrum.
Role
Melatonin is widely misunderstood as a sleep drug — a substance that makes you sleep — when it is actually a darkness signal that communicates time of day to every cell in the body. This misunderstanding produces two consequential errors: supplementing with pharmacological doses (1–10mg) when physiological doses (0.1–0.3mg) are sufficient for timing adjustments, and ignoring the far more powerful lever of eliminating the evening light that suppresses natural melatonin secretion. Thirty minutes of overhead light in the hour before bed can delay melatonin onset by 90 minutes — a circadian disruption equivalent to flying several time zones west, produced every night by the lighting choices of the majority of people in developed countries.