Melatonin

Melatonin gets its name from "melano" (dark) and "tonin" (tightening) because researchers first discovered it could lighten frog skin by concentrating melanin pigments. Yale dermatologist Aaron Lerner isolated it from bovine pineal glands in 1958, needing four tons of pineal tissue to extract just a few milligrams. What started as research into skin pigmentation accidentally unlocked one of nature's most universal biological clocks, present in everything from algae to humans.

Even a single photon hitting the retina can suppress melatonin production, but blue wavelengths (460-480nm) are 100 times more potent at disruption than red light. This explains why campfires never ruined our ancestors' sleep while scrolling your phone for two minutes at midnight can delay sleep onset by an hour. The practical fix is counterintuitive: dim red lights at night preserve melatonin while still letting you see, which is why submariners and astronomers work under red illumination.

Most melatonin supplements contain 3-10mg, but your brain naturally produces only 0.1-0.3mg per night—meaning people routinely take 10-100 times the physiological dose. This flooding approach can actually desensitize receptors and shift your circadian rhythm in unintended directions, which is why 0.3-0.5mg often works better for sleep than the horse-pill doses lining pharmacy shelves. Timing matters more than quantity: taking it 3-5 hours before desired sleep resets your clock, while taking it right at bedtime just makes you groggy.

About 70% of totally blind individuals have Non-24-Hour Sleep-Wake Disorder because their circadian rhythms free-run without light cues, gradually drifting later each day like a clock running slightly slow. Precisely timed melatonin (often combined with scheduled activities) can entrain their body clocks to Earth's 24-hour day, preventing the exhausting cycle of being awake all night every few weeks. This medical application revealed melatonin's role as a zeitgeber—a time-giver that coordinates biological rhythms even without eyes.

Beyond sleep, melatonin is an astonishingly potent antioxidant that can cross the blood-brain barrier and even enter mitochondria, protecting cellular powerhouses from oxidative damage. It doesn't just scavenge free radicals itself—it upregulates your body's own antioxidant enzymes like superoxide dismutase and glutathione peroxidase, creating a cascade effect. This dual role as both timekeeper and cellular protector suggests why melatonin production declines with age precisely when oxidative damage accelerates, though whether supplementation truly extends healthspan remains an open question.

In winter, your body secretes melatonin for 12+ hours nightly compared to 8 hours in summer, essentially putting you in biological hibernation mode even if you consciously resist it. This extended melatonin duration, not just low light exposure, drives the fatigue and depression of Seasonal Affective Disorder in vulnerable individuals. Light therapy at dawn works by shortening this melatonin signal back to summer-length, essentially biochemically convincing your body that winter is over—which is why afternoon light therapy often fails while morning light succeeds.