melatonin

Melatonin is an indoleamine hormone with the chemical name N‑acetyl‑5‑methoxytryptamine, synthesized predominantly in the pineal gland in response to darkness and suppressed by light exposure. In humans, approximately 30 micrograms are produced per night, with peak plasma concentrations typically between 80–120 pg/mL during nighttime and much lower daytime levels. Its discovery in 1958 marked a pivotal advance in understanding circadian biology. Unlike essential nutrients like vitamins or minerals, melatonin is a hormone, not obtained through diet, and thus has no established Recommended Dietary Allowance. Its endogenous production is governed by the light–dark cycle: photoreceptors in the retina convey light information to the suprachiasmatic nucleus, the body’s central circadian clock, which then regulates pineal melatonin synthesis and release into the bloodstream. Beyond its endocrine role, melatonin is synthesized in extrapineal tissues, including the gastrointestinal tract and mitochondria across various organs, where it may play paracrine and antioxidant roles. Because melatonin functions as a timekeeper for sleep–wake rhythms, it influences multiple physiological systems, including core body temperature regulation, immune modulation, and metabolic processes. Given its role in signaling night onset, melatonin has been widely studied both physiologically and pharmacologically, with supplement forms extensively used for sleep disorders. Despite being a naturally produced molecule, supplemental melatonin’s pharmacokinetics differ from endogenous secretion, contributing to ongoing research on optimal dosing, timing, and clinical applications.

Melatonin’s principal physiological role is the regulation of circadian rhythms and the timing of sleep onset. By acting on melatonin receptors MT1 and MT2 in the suprachiasmatic nucleus, melatonin signals the body that it is time to prepare for sleep, thereby helping decrease sleep‑onset latency. Supplemental melatonin has been shown in clinical contexts to aid sleep initiation and adjust circadian rhythms for conditions such as jet lag and shift work sleep disorder. Beyond circadian regulation, melatonin exhibits antioxidant and anti‑inflammatory properties, neutralizing reactive oxygen and nitrogen species and supporting cellular defense mechanisms. Recent narrative reviews have highlighted melatonin’s diverse biological activities, including potential roles in metabolic regulation, cardiovascular resilience, glycemic control, and gut microbiome interactions, although much of this evidence remains preliminary. Sleep quality improvements with melatonin supplementation have been observed, with some evidence indicating modest benefits in specific populations. The Sleep Foundation notes that melatonin can help individuals fall asleep at desired times and may improve sleep in circadian rhythm disorders and certain forms of insomnia, though it is not the first‑line treatment. Studies also explore melatonin’s effects on procedural anxiety, seasonal affective disorder symptoms, GERD, migraines, and neurodevelopmental disorders like autism or ADHD, where sleep disturbances are common. However, systematic evidence is mixed, and high‑quality randomized controlled trials are limited. While melatonin’s antioxidant capacity suggests broader protective roles, such as in neurodegeneration or cancer symptom management, robust clinical evidence is lacking, and these applications remain investigational rather than established. Additionally, melatonin influences immune responses and may interact with metabolic signaling pathways, although the clinical relevance of these effects requires further study. Overall, melatonin’s function extends beyond sleep regulation, but its health benefits outside sleep remain emerging areas with inconsistent data.

Unlike nutrients that are obtained through diet, melatonin is primarily produced endogenously in humans, and thus standard nutritional reference values like RDAs do not exist. Rather than daily intake requirements, clinicians focus on physiological circulating levels and supplemental dosing for specific clinical indications. Endogenous production usually follows a diurnal pattern with higher nocturnal release, and age influences synthesis, with older adults typically exhibiting reduced nocturnal peaks. Because melatonin’s role is regulatory rather than nutritive, there are no NIH‑defined dietary requirements. When used as a supplement, expert guidance often recommends low doses, typically 1–5 mg taken 30–60 minutes before bedtime to help with circadian alignment or sleep onset. Some authoritative sources recommend starting with the lowest effective dose, often 0.5–1 mg, and increasing only if needed, because higher doses do not necessarily improve efficacy and may increase side effects. For jet lag, documented doses range from 0.5 to 5 mg nightly after travel until circadian adjustment. In clinical practice, the dose and timing are individualized based on age, sensitivity, and the specific sleep issue. Pediatric use should only occur under medical supervision. Because melatonin is not an essential nutrient derived from food but a hormone synthesized internally, dietary intake does not determine requirement and there is no established optimal blood range used in nutrition recommendations.

Because melatonin is endogenously produced rather than obtained through diet, traditional deficiency syndromes typical of essential nutrients do not apply. Instead, clinicians refer to dysregulation or inadequate nocturnal secretion patterns, which are associated with sleep disturbances such as delayed sleep phase syndrome or insomnia. Low nocturnal melatonin levels have been implicated in circadian rhythm disruptions, especially in older adults whose pineal production declines with age—this decline correlates with increased prevalence of early waking and fragmented sleep characteristic of aging populations. Although not a nutritional deficiency, inadequate melatonin secretion can manifest as difficulty falling asleep, reduced sleep duration, or impaired circadian entrainment, particularly in individuals exposed to excessive evening light or shift work. Measurement of melatonin or its metabolites (such as 6‑sulfatoxymelatonin) in blood or urine can be used in research and clinical contexts to assess circadian phase and melatonin rhythm. However, routine clinical testing for melatonin levels is uncommon in general practice, and there are no universally accepted reference ranges for 'deficiency'. Populations at higher risk of circadian dysregulation include frequent travelers, shift workers, adolescents with delayed sleep timing, and older adults. Because melatonin influences multiple systems, research continues into its potential associations with mood disorders and neurodegenerative conditions, although causal links remain under investigation rather than established deficiency states.

Although melatonin is primarily produced endogenously, numerous plant and animal foods contain measurable melatonin, albeit in trace amounts far lower than supplemental doses. Tart cherries (Prunus cerasus) are among the best‑characterized dietary sources, with studies reporting melatonin content ranging from about 0.17 to 13.46 ng per gram of fruit. Consuming such foods can modestly raise circulating melatonin levels and support sleep patterns in some contexts. Nuts, especially pistachios and walnuts, contain melatonin and sleep‑promoting nutrients including tryptophan; walnuts also provide tryptophan which can be converted to melatonin. Goji berries are another fruit with relatively high melatonin content among plant foods. Milk contains both melatonin and its precursor tryptophan, and levels can be higher in milk collected at night. Other fruits like bananas, grapes, pineapple, plums, and oranges contain melatonin and supportive micronutrients that may enhance sleep. Grains such as rice and cereals contain melatonin, and herbs and olives also contribute small quantities. Because dietary melatonin content varies with growing conditions and processing, absolute values can differ widely. While foods with melatonin provide physiological trace amounts rather than therapeutic levels seen in supplements, incorporating a variety of these foods into evening meals or snacks may modestly support endogenous rhythms when combined with good sleep hygiene practices.

Exogenously consumed melatonin is well absorbed orally, with peak plasma concentrations occurring within 60–120 minutes after ingestion. However, oral bioavailability is variable due to first‑pass metabolism by the liver enzymes CYP1A2 and CYP2C19, meaning that actual systemic exposure can differ substantially between individuals. Foods containing melatonin provide nanogram quantities far below supplemental doses, and for most people, dietary melatonin does not significantly alter sleep‑wake patterns on its own. Factors influencing melatonin bioavailability include the presence of food, which can delay absorption, and interactions with medications that inhibit or induce key metabolizing enzymes. For example, CYP1A2 inhibitors like fluvoxamine can markedly increase melatonin exposure, while inducers such as cigarette smoke and certain anticonvulsants may reduce its blood levels. Melatonin crosses the blood–brain barrier and exerts effects centrally by binding to MT1 and MT2 receptors in the suprachiasmatic nucleus to influence circadian timing. Because melatonin clearance and sensitivity vary widely, individual response to supplemental doses may differ, and timing relative to endogenous rhythms (e.g., 30–60 minutes before desired sleep time) is critical for effectiveness. While food sources provide melatonin, their contribution to circulating levels is minor compared with supplemental forms.

Melatonin supplements are widely used for short‑term sleep disorders, including insomnia and jet lag, and for circadian rhythm disturbances. Health organizations typically recommend starting with a low dose, often 0.5–1 mg taken about 30 minutes before bedtime, and adjusting based on response, up to 3–5 mg. Immediate‑release formulations are commonly used for sleep onset issues, while sustained‑release forms may benefit sleep maintenance in certain cases. Evidence suggests melatonin can help reduce sleep‑onset latency and improve total sleep time in some individuals, particularly when sleep timing is disrupted. However, it is not considered a first‑line treatment for chronic insomnia by some expert bodies, and cognitive‑behavioral therapy for insomnia (CBT‑I) remains preferred for long‑term management. Experts emphasize consulting a healthcare provider before starting melatonin, especially for children, pregnant or lactating individuals, or those with medical conditions. Because supplements are not regulated as strictly as medicines, product quality and dosage accuracy vary, and choosing third‑party tested products can improve safety. Long‑term safety data are limited, and some observational research raises concerns about chronic use; therefore, melatonin may be most appropriate for occasional or short‑term use rather than nightly use indefinitely. As research evolves, individualized assessment of benefit, timing, and dose is recommended.

There is no formally established Tolerable Upper Intake Level for melatonin because it is not an essential nutrient with dietary intake recommendations. Supplemental dosing above what the body naturally produces can lead to side effects such as daytime drowsiness, dizziness, headaches, nausea, and vivid dreams. While low‑to‑moderate doses (1–5 mg) are generally considered safe for short‑term use, excessive doses (e.g., above 10 mg) have been associated with increased risk of adverse effects, including prolonged grogginess and altered blood pressure or glucose regulation in rare cases. Some literature suggests that even very high doses in experimental settings (e.g., >100 mg) do not consistently produce severe toxicity, but risks rise with supraphysiologic intake. Because supplements vary in potency and purity due to limited regulation, inadvertent excessive intake is possible, making third‑party verification important. Long‑term safety remains inadequately studied, and chronic nightly use should be guided by a healthcare provider, particularly in individuals with underlying health conditions.

Melatonin can interact with a range of medications due to its central role in circadian regulation and metabolism by cytochrome P450 enzymes. Medications that inhibit CYP1A2, such as fluvoxamine, can markedly increase melatonin levels and exposure, potentially enhancing sedative effects or side effects. Melatonin may interact with anticoagulants like warfarin, increasing bleeding risk, and with antihypertensive drugs, potentially causing additive blood pressure lowering. Interactions with central nervous system depressants, including benzodiazepines, alcohol, and opioids, can increase sedation and impairment. Certain antidepressants and oral contraceptives can raise melatonin concentrations, increasing risk of daytime drowsiness or headaches. Because melatonin can influence glucose and blood pressure, caution is advised when taken with diabetes medications or antihypertensives, and consultation with healthcare providers is essential. Given the broad range of potential drug interactions, individuals taking prescription medications should discuss melatonin use with their clinician.

Common Forms: Immediate‑release tablets, Sustained‑release capsules, Gummies, Liquid drops

Typical Doses: 0.5–5 mg taken 30–60 minutes before bedtime

When to Take: Evening, ~30 minutes before desired sleep

Best Form: Individualized; immediate release for sleep onset