Melatonin in Circadian Rhythm and Brain Health: Neuroprotective Effects and Therapeutic Potential.

Melatonin is an indole-like hormone secreted by the pineal gland. It regulates circadian rhythms and exerts antioxidants, anti-inflammatory, immunomodulatory, tumor-suppressing, and sleep-improving effects. With global population aging, neurodegenerative diseases have gained public attention. Melatonin has been increasingly studied for brain diseases. This review synthesizes evidence on melatonin in circadian rhythm regulation, Alzheimer's disease (AD), Parkinson's disease (PD), cerebral ischemia-reperfusion, depression, insomnia, brain aging and dietary applications. We critically evaluate study methodologies, sample sizes, and reproducibility. While melatonin shows promise, many findings derive from small clinical trials or animal models requiring validation. We conclude that melatonin may positively affect brain health through multiple pathways but emphasize that evidence strength varies across conditions. From a safety perspective, obtaining melatonin from food and dietary supplements is ideal for consumers.