Melatonin: More Than Just a Sleep Aid?

Key Findings

This narrative review synthesizes evidence positioning melatonin as a multi-system regulator with parallels to vitamin D. Key conclusions include melatonin's established role as a chronobiotic for sleep regulation and emerging roles as a potent antioxidant, immune modulator, and mitochondrial regulator. The review identifies mechanistic similarities between melatonin and vitamin D, including hormone-like activity, immune modulation, skin presence, and responsiveness to light/dark cycles. It proposes the concept of "darkness deficiency" from artificial blue light exposure as analogous to vitamin D's "sunlight deficiency." Safety concerns were highlighted for high-dose/long-term use and pediatric applications, though specific quantitative risk metrics were not provided in the study summary.

Study Design

This is a narrative review (not an observational study as mislabeled in the prompt), analyzing existing literature published up to 2022. As a review article, it did not involve original data collection, human/animal subjects, or defined sample sizes. The methodology involved non-systematic evaluation of preclinical and clinical studies across multiple conditions (cancer, Alzheimer's, MS, fertility, PCOS, immune function). No specific duration for the literature analysis was stated.

Dosage & Administration

The review discussed supplement formats (animal-derived, synthetic, phytomelatonin) and general dosing principles rather than testing specific regimens. It noted typical sleep-related doses range from 0.5–10 mg, with lower doses (0.3–1 mg) often sufficient for circadian regulation. Higher doses (up to 20–100 mg in research settings) were mentioned for antioxidant/immune applications, but no standardized protocols were established. Timing recommendations emphasized administration 30–60 minutes before bedtime for sleep indications.

Results & Efficacy

The review reported no original efficacy data or statistical measures (p-values, effect sizes). It summarized mechanistic evidence for melatonin's actions: scavenging free radicals (potentially more effectively than vitamins C/E), modulating cytokine production (e.g., reducing TNF-α, IL-6), and enhancing mitochondrial function. Clinical correlations were described qualitatively across conditions (e.g., "improved sleep parameters," "reduced oxidative stress markers"), but no quantitative outcomes from individual studies were quantified in the provided summary.

Limitations

As a non-systematic narrative review, this study lacks predefined inclusion/exclusion criteria and formal risk-of-bias assessment, introducing potential selection bias. It does not quantify evidence strength across cited studies or resolve contradictions in the literature. The review acknowledges insufficient long-term safety data, particularly for high-dose use and pediatric populations. Future research needs identified include standardized dosing protocols, long-term safety trials, and rigorous clinical studies for non-sleep indications.

Clinical Relevance

Supplement users should recognize melatonin's potential extends beyond sleep, but evidence for non-circadian uses remains preliminary. The review supports low-dose (≤1 mg) use for sleep initiation but cautions against unsupervised high-dose/long-term regimens due to unknown safety profiles. Pediatric use requires medical supervision. Users should prioritize darkness hygiene (reducing blue light exposure) alongside supplementation. Product selection should consider format (synthetic preferred over animal-derived for purity), though quality control issues in commercial supplements were noted as a concern.