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Melatonin

Melatonin featured article

Introduction

Melatonin isn’t just the “sleep hormone”—it regulates over 500 genes and plays a key role in the body’s antioxidant defenses.

As we age, melatonin production declines significantly. By the time a person reaches 50 years old, melatonin levels are 50% of what they were at age 20. By age 80, melatonin production can be ten times lower than in teenagers. This reduction in melatonin is linked to changes in sleep patterns, circadian rhythm disruption, and overall health as we age.

Melatonin supplementation isn’t just beneficial for sleep, it also increases antioxidant enzymes like glutathione and superoxide dismutase, decreases biomarkers of oxidative stress, reduces [systolic and diastolic blood...

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Q&A #70 with Dr. Rhonda Patrick (5/3/25)

Posted on May 15th 2025 (about 1 month)

Dr. Rhonda Patrick discusses cancer prevention, linoleic acid, shingles vaccine and dementia, creatine's kidney effects, and shares her overnight oats recipe.

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Q&A #62 with Dr. Rhonda Patrick (9/7/24)

Posted on September 23rd 2024 (9 months)

Dr. Rhonda Patrick discusses if smoked salmon is carcinogenic, high-dose melatonin, creatine on workout vs. non-workout days, and the Neurocode brain scan.

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Q&A #54 with Dr. Rhonda Patrick (12/2/23)

Posted on December 11th 2023 (over 1 year)

Dr. Rhonda Patrick explores melatonin's antioxidant properties, curcumin supplementation, antinutrients, and SARMs in her latest Q&A.

Topic Pages

  • Melatonin

    Melatonin is an indoleamine hormone synthesized nocturnally by the pineal gland, entraining circadian rhythms through MT1/MT2 receptor activation.

News & Publications

  • Melatonin supplementation may heighten DNA repair in night shift workers during daytime sleep, potentially reducing cancer risk. oem.bmj.com
    Cancer Sleep DNA Damage Circadian Rhythm Melatonin Supplements

    Working night shifts may increase the risk of cancer by disrupting the production of melatonin, a hormone essential for DNA repair. This disruption can impair the body’s ability to repair oxidative DNA damage, potentially contributing to cancer development. A recent study found that melatonin supplementation could improve the repair of oxidative DNA damage in night shift workers.

    The researchers conducted a four-week randomized, placebo-controlled trial with 40 night shift workers, providing them a 3-milligram dose of melatonin before their daytime sleep periods. They collected urine samples during daytime sleep and nighttime work periods, measuring 8-hydroxy-2′-deoxyguanosine (8-OH-dG), a marker of DNA repair capacity.

    They found that melatonin supplementation nearly doubled 8-OH-dG excretion during daytime sleep, indicating improved DNA repair. However, they observed no difference in 8-OH-dG excretion during the night shift. Although the melatonin group experienced a slight decrease in wakefulness after falling asleep, the researchers found no differences in total sleep duration or sleepiness levels between the two groups.

    The findings from this small study suggest that melatonin supplementation enhances oxidative DNA repair in night shift workers, offering the potential for reducing cancer risk. More extensive studies may identify optimal dosages and the long-term effects of melatonin supplementation in this population. Learn about the pros and cons of melatonin supplementation in this clip featuring Dr. Satchin Panda.

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  • Melatonin improves memory formation in mice, study finds. neurosciencenews.com
    Memory Melatonin

    Melatonin, often called the “sleepiness hormone,” regulates the sleep-wake cycle in mammals, modulates the expression of more than 500 genes, and exerts potent antioxidative and anti-inflammatory properties. A new study in mice suggests that melatonin also influences memory formation. Mice performed better on memory tests after receiving melatonin.

    Researchers gave male mice melatonin, ramelteon (a drug that activates melatonin receptors), and AMK (a melatonin metabolite) to assess their effects on memory formation while completing a task involving recognizing new objects. Then, they examined the compounds' effects on the phosphorylation (the addition of phosphate groups to proteins) of five key proteins associated with memory formation. To avoid potential variations in melatonin due to female reproductive cycles, the researchers did not investigate the compounds' effects on female mice.

    They found that when the mice received the three compounds immediately after learning, they formed long-lasting memories. However, the compounds exerted variable effects on the memory-related proteins depending on their location in the brain.

    These findings suggest that melatonin improves memory by influencing the phosphorylation of memory-related proteins, whether through receptors or other pathways in the brain. They also bring attention to the many ways in which melatonin, memory, and sleep are intricately linked. For example, sleep deprivation markedly impairs memory formation. Learn more in this clip featuring sleep expert Dr. Matthew Walker.

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  • Melatonin, commonly used to improve sleep, may aggravate bowel inflammation by increasing TNF-alpha in acute colitis medicalxpress.com
    Gut Microbiome Inflammation Melatonin

    From the abstract:

    In acute colitis, the hormone (melatonin) (MLT) led to increased clinical, systemic and intestinal inflammatory parameters. During remission, continued MLT administration delayed recovery, increased TNF, memory effector lymphocytes and diminished spleen regulatory cells. MLT treatment reduced Bacteroidetes and augmented Actinobacteria and Verrucomicrobia phyla in mice feces. Microbiota depletion resulted in a remarkable reversion of the colitis phenotype after MLT administration, including a counter-regulatory immune response, reduction in TNF and colon macrophages. There was a decrease in Actinobacteria, Firmicutes and, most strikingly, Verrucomicrobia phylum in recovering mice. Finally, these results pointed to a gut-microbiota-dependent effect of MLT in the potentiation of intestinal inflammation.

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  • A meta-analysis of more than 884 studies (RCTs) finds omega-3, folic acid and CoQ10 among the micronutrients that reduce cardiovascular risk. (2022) www.sciencedaily.com
    Vitamin D Vitamin C Omega-3 Melatonin Magnesium Curcumin Selenium Folate Zinc Polyphenol Carotenoids Cardiovascular Supplements

    Omega-3 fatty acids, folic acid, and CoQ10 reduce the risk of cardiovascular disease.

    Some nutritional components benefit cardiovascular health, but others have no effect on cardiovascular health or may even harm it, according to a recent study. Nutritional components providing the greatest benefit include omega-3 fatty acids, folic acid, and coenzyme Q10 (CoQ10), a vitamin-like compound produced in the body.

    Researchers analyzed the findings of more than 880 trials involving more than 880,000 participants that investigated the benefits of various macronutrients, micronutrients, and bioactive compounds on cardiovascular health.

    They found that the nutritional components had varied effects on cardiovascular health. For example, while omega-3 fatty acids, folic acid, and CoQ10 reduced the risk of cardiovascular disease, selenium and vitamins C, D, and E had no effect on the risk for either cardiovascular disease or type 2 diabetes (which often coincides with cardiovascular disease). On the other hand, beta-carotene (a vitamin A precursor) increased the risk of death from all causes. The researchers did not investigate the effects of the various nutritional components in combination versus alone.

    This analysis demonstrates that nutrition plays important roles in maintaining cardiovascular and metabolic health and supports the findings of large, epidemiological studies that have demonstrated that adherence to dietary patterns that are rich in omega-3 fatty acids, folic acid, and CoQ10, such as the Mediterranean Diet, for example, improves cardiometabolic health.

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  • Bedtime light exposure suppresses melatonin levels in children by 70 percent. onlinelibrary.wiley.com
    Sleep Melatonin

    Light is a major regulator of circadian rhythm, especially in children, whose eyes are more photosensitive. Previous research demonstrates that exposure to bright light suppresses melatonin (the sleepiness hormone) production twice as strongly in children as in adults. Authors of a new report found that children exposed to a wide range of light intensities experienced melatonin suppression that may decrease sleep quality.

    Light activates photosensitive cells in the retina that contain a pigment called melanopsin, which is most sensitive to blue light around 480 nanometers in wavelength. Melanopsin signaling is transmitted to a brain region called the suprachiasmatic nucleus, the master regulator of the circadian clock and a modulator of melatonin production. Previous research has demonstrated greater melatonin suppression in children exposed to home light levels (about 140 lux) compared to dim light (about 30 lux); however, additional studies are needed to understand how a wider range of light intensities affect melatonin suppression in young children.

    The researchers recruited parents of 36 children with good sleeping habits and asked them to complete a sleep diary for their children for seven days to assess baseline sleep quality. On the eighth day, the investigators transformed the participants' home into a dim-light environment by covering windows and installing low wattage light bulbs. Children entered the dim environment 4.5 hours before bedtime and the investigators measured their salivary melatonin levels every 20 to 30 minutes until one hour past bedtime. Children woke up in the morning and spent the entirety of the ninth day in the dim-light environment. One hour prior to bedtime, the investigators exposed children to light from an LED panel while playing and sampled melatonin levels again. The investigators set the LED panel to a single light intensity between 5 and 5,000 lux for each child based on a randomized pattern.

    During the one hour of light exposure prior to bedtime, salivary melatonin levels were suppressed by 69 to 98 percent across all light intensities; however, there was no overall dose-response. The investigators found that instead of light intensity and melatonin suppression changing at the same rate (as they do in a dose-response relationship), all light intensities induced high levels of melatonin suppression. Light intensities below 40 lux (i.e., dim light) tended to produce less melatonin suppression compared to intensities above 40 lux, but no other statistical trends were observed.

    These findings show that young children are highly susceptible to light before bedtime, especially light brighter than 40 lux (roughly equivalent to the amount of light provided by a 30 watt incandescent light bulb in a typical child’s bedroom). Further research is needed to understand how melatonin suppression relates to sleep quality.

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  • Melatonin use associated with lower risk for COVID-19. www.sciencedaily.com
    Melatonin COVID-19

    SARS-CoV-2 is the virus responsible for COVID-19. As SARS-CoV-2 infection rates climb, scientists continue to search for drugs that could be repurposed for COVID-19 treatment. Authors of a new multiomics study report that melatonin use dramatically reduced the likelihood of SARS-CoV-2 infection, especially for African Americans.

    Multiomics is an approach to data analysis that incorporates multiple levels of cellular biology, including the genome (DNA), transcriptome (RNA), and proteome (protein). The network of interactions between these multiple “omes” and a virus and its host is referred to as the interactome.

    The authors built multiomic data sets from several previous studies in humans, animals, and cell lines to investigate the SARS-CoV-2-host interactome. Based on these data sets, the authors identified 34 drugs that could be repurposed for COVID-19. Next, they reviewed the medical records of more than 18,000 participants for use of those drugs and presence of SARS-CoV-2 infection.

    They found that melatonin usage was associated with a 28 percent reduced likelihood of having a positive SARS-CoV-2 PCR test for the general population and 52 percent reduced likelihood for African Americans. The authors also reported similarities between the disease progression of COVID-19 and inflammatory bowel disease as well as inflammatory profiles of COVID-19 and asthma.

    This study used state-of-the-art data analysis to find associations between SARS-CoV-2 infection and a number of biological factors; however, clinical trials are needed to confirm the efficacy of melatonin supplementation in preventing or treating infection. This study has not yet completed peer-review.

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