Melatonin is a hormone produced primarily by the pineal gland — a small endocrine gland located deep within the brain. It is the body's primary chemical signal for night-time, playing a central role in regulating the circadian rhythm (the 24-hour internal body clock). Melatonin production rises sharply in the evening as light levels fall, peaks in the middle of the night, and then declines toward dawn as light exposure suppresses its release.
How melatonin is synthesised
The pineal gland synthesises melatonin from serotonin, which is itself derived from the amino acid tryptophan. The conversion pathway runs: tryptophan → 5-HTP → serotonin → N-acetylserotonin → melatonin. The final enzyme in this chain (HIOMT) is rate-limited by darkness — light hitting the retina sends signals via the suprachiasmatic nucleus (SCN) of the hypothalamus that suppress this enzyme's activity. This is why exposure to blue light from screens in the evening can reduce melatonin output.
What affects melatonin production
- Light: The single most important factor. Blue light (460–480 nm wavelength) is most suppressive. Dimming lights in the evening and using blue light filters can help preserve natural melatonin secretion.
- Age: Melatonin production declines with age. Older adults often produce less melatonin than younger people, with the sharpest decline typically occurring in midlife.
- Shift work and jet lag: Disruptions to the circadian schedule — shift work, long-haul travel across time zones — desynchronise the melatonin cycle from the environmental light-dark cycle.
Melatonin as a supplement
Supplemental melatonin is widely used as a chronobiotic — a substance that shifts the timing of the body clock — rather than a sedative. Its primary evidence-based applications are jet lag and shift work adaptation, where taking low-dose melatonin at the appropriate local time helps re-anchor the circadian rhythm. Evidence for its use in primary insomnia is more modest: it reduces sleep onset latency (how long it takes to fall asleep) by roughly 7–12 minutes on average, according to meta-analyses.
Dosing: less is more
Research suggests that melatonin is effective at much lower doses than those commonly sold commercially. Most studies on circadian rhythm shifting use 0.5–1 mg. Higher doses (5–10 mg) produce blood levels far exceeding what the body naturally produces and are not proportionally more effective for most people. The American Academy of Sleep Medicine and other clinical bodies generally recommend starting at the lowest effective dose.
Melatonin supplements in Lebanon
Supplements & More carries melatonin supplements from US brands at various dosages, delivered across Lebanon with cash on delivery.