Melatonin Is More Than a Sleep Hormone
How one of the body's most important signaling molecules became misunderstood—and why the science tells a much bigger story.
If I hear one more person tell me, “Don’t take melatonin—your body will stop making it,” I’m going to lose my mind. Somewhere along the way, melatonin developed a reputation as a dangerous sleep supplement that your body becomes “dependent” on.
The problem? That’s not what the science says. More importantly, it isn’t even asking the right question. Most people think melatonin is a sleep hormone. Sleep is simply one of the many things melatonin does.
In reality, melatonin is one of the body’s most important signaling molecules. It helps coordinate circadian rhythms, protects mitochondria, regulates immune function, reduces oxidative stress, controls inflammation, supports cellular repair, promotes autophagy, protects the brain, and influences cancer biology.1
Researchers now recognize melatonin as a master regulator of cellular resilience—not simply something that helps you fall asleep. That distinction matters because we’ve spent decades treating melatonin like a sleeping pill instead of recognizing it as a molecule involved in nearly every aspect of healthy aging.
Melatonin Is More Like Vitamin D Than a Sleep Aid
One of the most interesting ideas in recent melatonin research is that we’ve been thinking about melatonin the wrong way.
A 2022 review published in Nutrients argues that melatonin may have more in common with vitamin D than with a typical sleep supplement. Like vitamin D, melatonin influences multiple organ systems, helps regulate immune function, reduces inflammation, supports healthy mitochondria, and acts as a signaling molecule throughout the body.2
The authors even introduce the concept of “darkness deficiency.” Just as many people don’t get enough sunlight to maintain healthy vitamin D levels, modern life may expose us to too much artificial light at night. Phones, tablets, televisions, LED lighting, and shift work can all suppress the body’s natural nighttime production of melatonin, potentially affecting much more than sleep.
Your Body Already Makes Melatonin and Less of It Every Year.
One fact that receives surprisingly little attention is that melatonin production declines with age—and it begins earlier than most people realize.
According to Joseph Arendt’s review in Endotext, nighttime melatonin secretion gradually decreases with aging. After approximately 35 to 40 years of age, the amplitude of the normal nocturnal melatonin rhythm begins to decline, although the degree of reduction varies considerably among individuals. By older adulthood, many people produce only a fraction of the nighttime melatonin they did as young adults.3
That decline refers primarily to pineal melatonin—the melatonin released into the bloodstream each night that acts as the body’s hormonal signal of darkness. This nightly surge helps synchronize circadian rhythms that influence sleep, hormone secretion, metabolism, immune function, and tissue repair.
What’s often overlooked is that the pineal gland is not the body’s only source of melatonin. Research over the past two decades has shown that many tissues—including the gastrointestinal tract, bone marrow, skin, retina, placenta, immune cells, and even mitochondria within individual cells—also synthesize melatonin locally. Unlike pineal melatonin, which circulates throughout the body, this extrapineal melatonin is largely used where it is produced to help defend cells against oxidative stress, regulate inflammation, and maintain normal mitochondrial function.4
In other words, the body’s need for melatonin doesn’t disappear as we age. If anything, it increases. Aging is accompanied by greater oxidative stress, chronic low-grade inflammation, mitochondrial dysfunction, and circadian disruption—the very biological processes that melatonin helps regulate.
Think about that for a minute…
We readily acknowledge that estrogen, progesterone, testosterone, thyroid hormone, growth hormone, and DHEA decline with age. No one argues those hormones suddenly become unnecessary after age thirty, yet when melatonin production declines, many people are told they should simply accept poorer sleep, diminished recovery, greater oxidative stress, and circadian disruption because replacing it is somehow “unnatural.” That argument has doesn’t make biological sense.
What Does Melatonin Have to Do with Cancer?
Quite a bit, as it turns out. As we get older, our cells are exposed to more wear and tear. They accumulate damage from inflammation, oxidative stress (sometimes called “rusting” inside the body), problems with energy production, and mistakes that occur when cells divide. These are some of the same changes scientists see during the early stages of cancer.5
This is where melatonin becomes interesting because it helps protect cells from oxidative stress, supports healthy mitochondria, calms excessive inflammation, helps regulate the immune system, and keeps our internal body clock running on time. These are all systems that help the body repair damage before it becomes a bigger problem. That doesn’t mean melatonin prevents every cancer or treats cancer by itself, but it does help explain why researchers have spent more than 30 years studying melatonin in cancer biology.
In laboratory studies, melatonin has been shown to slow the growth of some cancer cells, reduce the formation of new blood vessels that feed tumors, encourage damaged cells to die when they should, support the immune system, and even reduce some of the side effects of chemotherapy and radiation.6
That’s why melatonin is no longer viewed as simply a sleep hormone. Scientists now recognize it as a molecule that helps protect cells from many of the biological changes that contribute to aging and disease—including cancer.
Breast Cancer: Where We Have the Most Evidence
The strongest research on melatonin and cancer has been in breast cancer. One reason is its relationship with estrogen.
Estrogen helps many breast cancers grow. Researchers have found that melatonin can reduce estrogen signaling in two important ways. First, it can make breast cancer cells less responsive to estrogen. Second, it can decrease the activity of aromatase, the enzyme that helps produce estrogen in breast tissue.7
Melatonin also appears to help in other ways. Laboratory studies have shown that it can slow the growth of breast cancer cells, reduce oxidative DNA damage, decrease inflammation, improve immune function, and reduce the growth of new blood vessels that tumors need to survive.
Researchers have also noticed women who work night shifts for many years have higher rates of breast cancer than women who work during the day. One possible reason is that exposure to light at night suppresses the body’s natural melatonin production and disrupts normal circadian rhythms.8
Researchers are also studying whether low melatonin levels increase the risk of endometrial cancer. The evidence is not as strong as it is for breast cancer, but the biology is similar. Lower melatonin may lead to more estrogen activity, more inflammation, greater oxidative stress, and poorer metabolic health—all of which may increase cancer risk.9
None of this means melatonin is a cure for cancer, but it does support the argument that we’ve been underestimating one of the body’s most important protective molecules.
Melatonin Is Showing Up in Much More Than Sleep Research
If melatonin were simply a sleep supplement, researchers wouldn’t be studying it in conditions as different as Long COVID and post-vaccine injury, depression, sepsis, Alzheimer’s disease, and cancer. The reason they are is because all of these conditions share something in common: they involve oxidative stress, inflammation, mitochondrial dysfunction, immune system changes, or disruption of the body’s normal circadian rhythm. This pattern of what melatonin does in the body is becoming more and more important.
Long COVID and Post-Vaccine Injury
One of the best examples is Long COVID and post-vaccine injury. During my time at FLCCC, I helped digest hundreds of articles with the team on the pathology of spike protein related diseases. We put together treatment strategies to help people suffering with symptoms from these inflammation disorders.
Research has shown that persistent inflammation, oxidative stress, mitochondrial dysfunction, and immune dysregulation contribute to many of the lingering symptoms people experience after COVID-19. Because melatonin helps regulate all of these pathways, it was included in the FLCCC I-RECOVER protocol as part of a broader strategy to support recovery.10
Depression
Most people think depression is simply a chemical imbalance. We now know it’s much more complicated. Many people with depression also have disrupted circadian rhythms, poor sleep, increased inflammation, and changes in the way their brain cells produce energy. Researchers have spent years studying melatonin and medications that act on melatonin receptors because improving circadian rhythm may improve mood in some patients.11
Sepsis
Sepsis is one of the most dangerous inflammatory conditions seen in medicine. When the immune system overreacts to an infection, it can damage organs throughout the body. Research shows that melatonin, because it appears to reduce oxidative stress, calms excessive inflammation, protects the mitochondria, and supports normal immune function.12 Vitamin C is also another critical nutraceutical in the treatment of sepsis and oxidative stress.
Brain Health
As we age, our brains become more vulnerable to oxidative stress, inflammation, poor sleep, and declining mitochondrial function. These same processes are believed to contribute to Alzheimer’s disease and other forms of dementia. Melatonin is being studied for its protective effects on brain cells, preserving mitochondrial function, and improving sleep—all of which are important for long-term brain health.13
The Bottom Line
After reviewing the research, I think it’s clear what the story is surrounding the body and melatonin. I encourage you to read through the references yourself and draw your own conclusions.
Melatonin is made naturally by the body. It helps coordinate our circadian rhythm, protects mitochondria, reduces oxidative stress, regulates inflammation, supports immune function, and helps maintain healthy cells throughout the body.
Like every hormone and signaling molecule, melatonin changes with age. That doesn’t automatically mean everyone should take a supplement. The right dose, timing, and whether supplementation is appropriate depends on the individual and should be discussed with a knowledgeable healthcare professional. One of the greatest ways to increase your body’s melatonin levels is to get outside in the late afternoon for sunlight. Also, did you know that eating pistachios is equivalent to taking a melatonin supplement?
The idea that melatonin is simply “a sleep supplement” or that taking it inevitably causes the body to “stop making its own” doesn’t reflect what decades of research have taught us. It is one of the body’s most important molecules for maintaining cellular health.
Your Next Step is Understanding Your Own Biology
Melatonin is only one piece of the puzzle. Light exposure, sleep habits, stress, nutrition, movement, gut health, inflammation, hormones, and mitochondrial health all influence how well your body produces and uses this remarkable molecule.
If you’re struggling with poor sleep, low energy, brain fog, sports injury, slow recovery, chronic inflammation, or simply don’t feel like yourself anymore, those symptoms deserve more than a quick fix.
My approach is to look at the whole picture.
Through personalized health and performance coaching, I help people identify the root causes affecting their health and develop practical strategies to support healthy sleep, improve recovery, optimize circadian rhythms, reduce inflammation, and create the conditions that allow the body to function the way it was designed to. Sometimes that includes melatonin supplementation. Often it starts with helping your body make better use of the melatonin it’s already designed to produce.
If you’re ready to stop guessing and start building a plan based on your own body’s science and your individual health, I’d love to help you.
Book a free discovery call and let’s talk about your health goals.
Ferlazzo N, Andolina G, Cannata A, et al. “Is Melatonin the Cornucopia of the 21st Century?” Antioxidants 9, no. 11 (2020): 1088.
Minich DM, Henning M, Darley C, et al. Is Melatonin the “Next Vitamin D”?: A Review of Emerging Science, Clinical Uses, Safety, and Dietary Supplements. Nutrients. 2022;14(19):3934.
Arendt J. Physiology of the Pineal Gland and Melatonin. In Endotext. MDText.com, 2022. This covers the classic endocrine role of the pineal gland and melatonin as the hormonal signal of darkness.
Arendt J. Physiology of the Pineal Gland and Melatonin. In Endotext. MDText.com, 2022. This covers the classic endocrine role of the pineal gland and melatonin as the hormonal signal of darkness.
Reiter, Russel J., Dun-Xian Tan, Sergio Rosales-Corral, et al. “Melatonin as a Full Service Anti-Cancer Agent: Inhibition of Initiation, Progression and Metastasis.” International Journal of Molecular Sciences 18, no. 4 (2017): 843.
Mehrzadi, Sara, et al. “An Updated Review of the Mechanistic Potentials of Melatonin Against Cancer.” Frontiers in Pharmacology 12 (2021): 667592.
Sánchez-Barceló, Emilio J., et al. “Melatonin–Estrogen Interactions in Breast Cancer.” Journal of Pineal Research 38, no. 4 (2005): 217–222.
Schernhammer, Eva S., Francine Laden, Frank E. Speizer, Walter C. Willett, David J. Hunter, Ichiro Kawachi, Graham A. Colditz, and Susan E. Hankinson. “Rotating Night Shifts and Risk of Breast Cancer in Women Participating in the Nurses’ Health Study.” Journal of the National Cancer Institute 93, no. 20 (2001): 1563–1568.
Viswanathan, Annekathryn N., et al. “Circulating Melatonin and the Risk of Breast and Endometrial Cancer in Women.” Cancer Research 68, no. 21 (2008): 8540–8545.
Front Line COVID-19 Critical Care Alliance (FLCCC). I-RECOVER: Long COVID Treatment Protocol.
Geoffroy, Pierre A., et al. “Melatonin and Melatonin Agonists in Mood Disorders.” Current Pharmaceutical Design 21, no. 24 (2015): 3430–3441.
Colunga Biancatelli, Roberto M., Michael Berrill, Yousif H. Mohammed, and Paul E. Marik. “Melatonin for the Treatment of Sepsis: The Scientific Rationale.” Journal of Thoracic Disease 12, Suppl. 1 (2020): S54–S65.
Cardinali, Daniel P. “Melatonin and Healthy Brain Aging.” Frontiers in Endocrinology 10 (2019): 123.