Melatonin

What melatonin actually does in your body

Melatonin is a hormone made primarily by the pineal gland when it gets dark. Production follows a tight daily rhythm: levels start climbing about 2 hours before your usual bedtime (a point researchers call dim light melatonin onset, or DLMO), peak between 2:00 and 4:00 AM, and drop to nearly zero by morning. This signal doesn't just control when you feel sleepy. It coordinates liver metabolism, immune function, hormone release, DNA repair, and core body temperature across a 24-hour cycle.

Here's the problem: artificial light at night, especially the blue wavelengths (460-480 nm) from screens, LEDs, and fluorescent bulbs, can suppress pineal melatonin output by 50-90% ^[1]. That's not a small dip. It's enough to delay sleep onset, fragment sleep architecture, and set off a chain of metabolic disruptions.

More than a sleep hormone

Melatonin is one of the strongest antioxidants the body produces. It directly neutralizes hydroxyl radicals and reactive oxygen species, and unlike most antioxidants, it dissolves in both water and fat. That means it can cross cell membranes and the blood-brain barrier to protect nearly every compartment inside a cell. It also triggers the production of other antioxidant enzymes, including superoxide dismutase, glutathione peroxidase, and catalase ^[2].

On the immune side, melatonin boosts natural killer cell activity, supports T-helper cell function, and damps down inflammation by inhibiting NF-kB signaling. Production declines roughly tenfold between adolescence and old age ^[3]. Some researchers think this drop contributes to immunosenescence, the gradual weakening of the immune system that makes older adults more vulnerable to infection and chronic disease.

Melatonin and the gut

The gastrointestinal tract produces about 400 times more melatonin than the pineal gland ^[4]. This gut-derived melatonin doesn't enter general circulation the way pineal melatonin does. Instead, it works locally: regulating gut motility, protecting the intestinal lining, and communicating with the microbiome. Recent research shows a two-way relationship. Certain gut bacteria influence melatonin synthesis in the intestinal wall, and melatonin in turn shapes microbiome composition by reducing oxidative stress in the gut environment ^[4]. This is still an early research area, but it adds weight to the idea that melatonin's role extends well beyond sleep.

Supplementation: less is usually more

Melatonin supplements are easy to buy and widely used, but most people take far too much. The dose that mimics what the body naturally produces is 0.3-0.5 mg. Commercial products commonly contain 3-10 mg, which is 10-30 times the physiological amount. A 2024 dose-response meta-analysis found that sleep benefits peak at around 4 mg/day and higher doses don't add further improvement ^[5]. Lower doses (0.3-1 mg) often work just as well for simple sleep onset trouble, with fewer side effects like next-day grogginess and vivid dreams.

Timing matters as much as dose. Taking melatonin 2-3 hours before your target bedtime, rather than right at bedtime, better aligns with the body's natural DLMO window and produces stronger effects on sleep latency ^[5].

• For sleep onset: 0.3-1 mg taken 1-3 hours before desired bedtime
• For jet lag or shift work: 0.5-3 mg timed to the target sleep schedule
• Extended-release forms can help people who wake frequently during the night
• Sublingual tablets bypass liver metabolism and act faster

Quality control is a real issue

A 2017 study tested 31 melatonin supplements and found that actual melatonin content ranged from 83% less to 478% more than what the label claimed ^[6]. Over 70% of products missed their label claim by more than 10%. Worse, 26% of products contained serotonin as an unlisted contaminant. If you take melatonin, choose products with USP Verified or NSF Certified marks. These indicate independent testing for identity, potency, and contaminants.

Optimizing your own melatonin production

Before supplementing, try fixing your light environment first. Bright light exposure (ideally sunlight) within 30-60 minutes of waking anchors the circadian clock and ensures a strong evening melatonin rise. In the 2-3 hours before bed, dim the overhead lights, use blue-light-blocking glasses if needed, and switch to warm-toned lamps. A completely dark, cool bedroom supports maximal melatonin secretion through the night.

Regular exercise, especially earlier in the day, supports healthy melatonin rhythms. Tryptophan-rich foods (turkey, eggs, nuts, seeds) provide the raw material for serotonin, which the pineal gland then converts to melatonin. Magnesium and vitamin B6 are cofactors in this conversion pathway.