Melatonin

Melatonin is a hormone and signaling molecule produced by the pineal gland at night and also by many tissues, including mitochondria-rich cells. In cancer discussions, it is connected with circadian rhythm regulation, sleep quality, antioxidant defenses, mitochondrial function, immune modulation, estrogen signaling, tumor metabolism, and the possible consequences of light exposure at night. It is also discussed as a supportive-care agent for sleep disruption, fatigue, mood, nausea, and treatment-related toxicity in some cancer settings.

Evidence Snapshot

The evidence base is mixed. Laboratory and animal studies show many anticancer mechanisms, including effects on oxidative stress, apoptosis, angiogenesis, metastasis, estrogen receptor signaling, and tumor metabolic rhythms. Human studies include small randomized trials, older Lissoni-era oncology trials, quality-of-life trials, and more recent systematic reviews. Some reviews report signals for improved survival, tumor response, or reduced side effects when melatonin is added to standard care, while Cochrane and other cautious summaries emphasize that many studies are small, older, or at risk of bias.

How It Is Commonly Discussed

In integrative oncology, melatonin is usually framed as a low-cost supportive supplement and circadian-health intervention, not as a replacement for surgery, chemotherapy, radiation, immunotherapy, or targeted therapy. Some clinicians emphasize sleep, darkness at night, and circadian regularity; others discuss higher-dose melatonin as an investigational adjunct. Breast cancer, prostate cancer, lung cancer, advanced solid tumors, and chemotherapy-related toxicity are recurring topics in the literature.

Safety and Practical Cautions

Melatonin can cause sleepiness, vivid dreams, headache, dizziness, mood changes, next-day grogginess, or interaction concerns. It may affect blood pressure, anticoagulants, sedatives, seizure thresholds, immune-modulating drugs, diabetes medications, hormone-sensitive conditions, surgery timing, and clinical trial eligibility. Cancer patients should discuss melatonin with their oncology team, especially when using high doses, active chemotherapy, immunotherapy, endocrine therapy, anticoagulation, or multiple sedating medications.