RHR: The Melatonin Problem

In this episode we discuss:

• Why melatonin is better understood as a hormonal signal for the body’s internal clock than as a traditional sleeping pill
• How melatonin can influence circadian rhythm and why more isn’t necessarily better
• What a recent study found regarding long-term melatonin use and heart failure, and the limitations of those findings
• Why label accuracy is a significant concern, including research finding substantial variation between labeled and actual melatonin content
• Concerns surrounding melatonin use in children
• Why addressing light exposure, screen use, sleep timing, stress, and circadian consistency may be more effective than relying on nightly supplementation
• Strategies for supporting healthy sleep and the role of supplements as support once foundational sleep habits are established

Show notes:

• Long-term melatonin use and incident heart failure in adults with chronic insomnia by Nnadi, E., et al.
• “Effect of Ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysis” by Cheah, K. L., et al.
• “Quantity of melatonin and CBD in melatonin gummies sold in the US” by Cohen, P. A., et al.
• “Melatonin natural health products and supplements: Presence of serotonin and significant variability of melatonin content” by Erland, L. A. E., & Saxena, P. K.
• “Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans” by Gooley, J. J., et al.
• “Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: A randomized controlled trial” by Hidese, S., et al.
• “Melatonin and cardiovascular risk: An NHANES reality check after recent heart failure concerns” by Khan, B., & Lima, B. B.
• “Pediatric melatonin ingestions — United States, 2012–2021” by Lelak, K., et al.
• “Effects of saffron on sleep quality in healthy adults with self-reported poor sleep: A randomized, double-blind, placebo-controlled trial” by Lopresti, A. L., et al.
• “Oral magnesium supplementation for insomnia in older adults: A systematic review & meta-analysis” by Mah, J., & Pitre, T. 
• “Melatonin supplementation, hyperprolactinemia, and incident heart failure: A proposed prolactin-mediated pathway for cardiovascular risk” by Savvidis, C., Thomopoulos, C., & Ilias, I. et al.
• “Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study” by Windred, D. P., et al.
• “Melatonin treatment for age-related insomnia” by Zhdanova, I. V., et al.
• Learn more about Adapt Naturals Bio-Avail Mag, Steady Spirit, or take our quiz to see which products best suit your needs
• If you’d like to ask a question for Chris to answer in a future episode, submit it here
• Follow Chris on Instagram or Facebook

Hey everybody, Chris Kresser here. Welcome to another episode of Revolution Health Radio. Today we’re going to talk about melatonin. Walk into any grocery store or pharmacy, and you’ll see an entire shelf of bottles, gummies, sprays, and chewables, in doses ranging from a fraction of a milligram to 10 or 20 milligrams, sitting right next to the vitamin C. According to the CDC, U.S. sales nearly tripled between 2016 and 2020, and a lot of the people buying it take it every single night, year after year. Parents give it to toddlers, teenagers take it before exams. It’s become the default answer to “I can’t sleep.”

I have a nuanced relationship with melatonin. I recommended it in my practice for years in specific situations, and I still think it has a legitimate place. So this isn’t going to be an episode where I tell you melatonin is poison and you should throw it out. But I’ve grown increasingly concerned by the way I’m seeing melatonin recommended and used by both adults and kids, so I wanted to dedicate a show to the topic. This is especially timely, because a large observational study presented at the American Heart Association Scientific Sessions found that people with chronic insomnia who use melatonin for a year or more had close to double the risk of developing heart failure over the next five years compared to matched people who didn’t use it. That headline went crazy, as you can imagine. But it also got some of the details wrong, and I’ll walk through what the study can and can’t tell us later in this episode because the nuance matters a lot here. The bigger issue isn’t one study, it’s the belief underneath the whole melatonin phenomenon, which goes something like this: Melatonin is a natural hormone that our bodies make on their own, so taking it must be harmless. That belief’s doing a lot of work, and it doesn’t hold up. Melatonin is a hormone. Hormones are powerful. We wouldn’t take thyroid hormone or cortisol every night for a decade without asking what it was doing to us, and melatonin deserves the same respect.

By the end of this episode, you’ll understand what melatonin does in the body and why it’s a signal rather than a sedative, what the heart failure study really showed, why the bottle on your nightstand may contain far more or far less than what the label says, why I’m especially concerned about kids, and what I did with patients instead of melatonin that worked far better over the long run. Let’s dive in.

Melatonin is a hormone produced mainly by the pineal gland, a small structure deep in the brain. Its production is controlled almost entirely by light. When light hits the retina, especially the blue-enriched light of daytime, the signal travels to the master clock in the hypothalamus, which suppresses melatonin. When darkness falls, that break comes off and melatonin rises, typically starting a couple of hours before your habitual bedtime, peaking in the middle of the night, and tapering off toward morning. So the job of melatonin isn’t to knock you out. Its job is to tell every cell in your body what time it is. It’s a signal, not a sedative. That’s exactly how I used to explain it to patients because the distinction changes how you’d use it. A sedative makes you sleepy regardless of timing. A signal only works if it arrives at the right moment and in the right amount, and it works by shifting your internal clock rather than by sedating you. That’s also why melatonin isn’t a sleeping pill in any meaningful sense. In the trials that show a benefit for people with ordinary insomnia, the effect on falling asleep is small, only a matter of a few minutes. It’s far more effective at shifting your circadian rhythm, which is why it has a real role in jet lag and in helping someone whose body clock has drifted late pull their bedtime earlier.

There’s a second piece to this that often gets left out of the discussion. Melatonin is a hormone, and like every hormone, it has receptors all over the body, not just in the brain. There are melatonin receptors in the heart and blood vessels, in the pancreas, in the gut, in the reproductive organs, and throughout the immune system. So melatonin influences blood pressure, body temperature, insulin release, and the timing of reproductive hormones.

When you take it as a supplement, you’re not just nudging sleep, you’re sending a hormonal message to all of those tissues at once, and in most cases at a dose that’s many times higher than anything your pineal gland would ever produce. None of that means melatonin is necessarily dangerous in the way a prescription drug can be dangerous. It has a good short-term safety record. But “natural” and “harmless” are not the same word, and once you understand that melatonin is a systemic hormone rather than a gentle sleep herb, the idea of taking it every night for years starts to look questionable, and that’s especially true for kids and teens.

My own thinking here has evolved. Earlier in my career, I’d list melatonin as a reasonable option for people who had already tried magnesium and other approaches, at low doses, and I still think that was defensible given what we knew. What changed was watching what happened when “a low dose for a few weeks” turned into “five milligrams every night for six years,” which is what it did turn into for many people. By the end of my time in practice, I was recommending it for one purpose only, shifting their circadian rhythm in the short term, when that shift is what you want. Crossing several time zones is the classic case. Someone whose bedtime has drifted to two in the morning and who wants to pull it back to 11 is another. In both situations, you use a small dose, time carefully, for a handful of days, and then you stop, because the goal was to move the clock, and once the clock’s moved, the job is done.

That brings us to the study that put melatonin in the headlines. Researchers used a large database of electronic health records to identify about 130,000 adults with chronic insomnia. Roughly half had melatonin documented in their records for at least a year, and the other half were matched on around 40 factors, including age, other health conditions, and medications, with no melatonin use. Anyone who already had heart failure or was on other sleep medications was excluded. Then they looked forward five years. The melatonin group had a heart failure diagnosis rate of about 4.6 percent compared to 2.7 percent in the matched group, which is where the 90 percent higher risk figure comes from. They were also more than three times as likely to be hospitalized for heart failure and nearly twice as likely to die from any cause during the follow-up period. Those are striking numbers, but there are several important caveats. First, this was a conference presentation, not a peer-reviewed publication. As of this recording, the full paper hasn’t been published, and a commentary in the World Journal of Experimental Medicine earlier this year made exactly that point, while proposing some possible mechanisms.

Second, it’s observational; it shows an association, not cause and effect. And if you’ve been listening to this podcast for any length of time, you know what trouble we can get into when we assume that correlation equals causation. It often doesn’t. Third, and related, people who end up with melatonin in their medical records for a year or more are not the same as people who don’t. They tend to have worse insomnia, more depression and anxiety, and more contact with the healthcare system, and all of those things independently are associated with higher cardiovascular disease risk. The researchers didn’t have data on insomnia severity or psychiatric history, so they couldn’t fully account for this.

Fourth, in the U.S. melatonin is over the counter, so a lot of real-world use never shows up in a medical record. Some of the non-users in this study were almost certainly taking it. A separate analysis in the journal Open Heart, also published this year, looked at nationally representative survey data and found that melatonin users differed dramatically from non-users at baseline, particularly in sleep disturbance and depression, and that after adjusting for those differences, melatonin use wasn’t associated with having heart failure. That analysis was a snapshot in time, not a five-year follow-up, so it isn’t a direct rebuttal of this first study. The authors were careful to say that their data can’t prove safety either. What they can say is that the alarm signal needs to be tested properly before anyone concludes melatonin causes heart failure.

Melatonin has become one of the most popular over-the-counter sleep supplements in the United States, with adults and children increasingly using it on a nightly basis. But melatonin is a hormone—not simply a natural sleep aid—and understanding how it works can change the way we think about supplementation. #ChrisKresser #melatonin

So where does that leave us? We don’t know whether long-term melatonin use harms the heart. We do know that a large study found a signal worth taking seriously, and we know that the assumption of safety was never based on long-term data in the first place. There has never been a trial of nightly melatonin over five or 10 years. People have simply been running that experiment on themselves and on their children without a control group. That alone should make us more cautious than we’ve been.

There’s a more immediate problem with melatonin, though, and it has nothing to do with the heart. It has to do with what’s in the bottle. Melatonin is regulated as a dietary supplement in the U.S., which means it’s not verified when the product hits the shelf like a medication would be. In 2017, researchers in the Journal of Clinical Sleep Medicine tested 31 melatonin supplements and found that the actual content ranged from 83 percent below the label claim to 478 percent above it. More than 70 percent of the products missed their label claim by more than 10 percent, and the same product could vary by hundreds of percent from one lot to the next. A quarter of them also contain serotonin, a controlled substance that shouldn’t be there at all. Then in 2023, a research letter in JAMA tested 25 melatonin gummies, the form most parents reach for. 22 of the 25 were mislabeled, with actual content running anywhere from 74 to 347 percent of what the package said. Several also contained CBD that wasn’t disclosed. If you bought a gummy labeled three milligrams, you might have been getting 10, or you might have been getting 100 micrograms. It’s very hard to tell.

Dose matters more with melatonin than people realize because the effective dose is tiny. In a randomized trial in the Journal of Clinical Endocrinology and Metabolism, researchers gave older adults with insomnia three different doses of melatonin and a placebo. The dose that worked best was 0.3 milligrams, or 300 micrograms, which incidentally is roughly what the body produces on its own. It restored sleep efficiency and normalized nighttime melatonin levels. The three milligram dose, which is on the low end of what’s sold in stores, also helped with sleep but left melatonin levels elevated well into the next day. A hormone that’s supposed to be gone by morning was still circulating at lunchtime, and that could explain the grogginess that many people feel the next day after taking melatonin.

So compare that 300 microgram dose to what you typically see in stores. Three to five milligrams is standard, 10 to 20 milligrams is not uncommon to see, and that’s 30 to 60 times the physiologic dose, with a manufacturing process that might double or triple it without telling you. When I recommended melatonin in my practice, I typically suggested microgram quantities, like 300 micrograms, not milligrams. This also helps explain something I saw over and over. High doses of melatonin can leave people feeling groggy and foggy the next morning, and some people report a paradoxical effect. Melatonin helps them fall asleep, but then they snap awake at three or four in the morning with a racing heart and a wired feeling, as if their body is flipped into fight-or-flight. I heard that description from a lot of patients. Whether it’s a rebound in cortisol, a disruption of the normal melatonin curve, or a dose that overshoots and then crashes, the pattern was consistent enough that I stopped being surprised by it. Melatonin is supposed to be a gentle rise and a gentle fall, and that is probably what happens when you take a dose of, say, 300 micrograms. But when you take a big pharmacologic dose of five to 10 milligrams, the effects can be unpredictable.

And unfortunately, the group most exposed to all of this is children. Melatonin use in kids has exploded. A 2022 report from the CDC in The Morbidity and Mortality Weekly found that calls to poison control centers for pediatric melatonin ingestion increased 530 percent between 2012 and 2021, over 260,000 cases in total. By 2020, melatonin had become the single most frequently ingested substance reported to poison control for children. Most of those were accidental, kids getting into gummies that look and taste like candy. But hospitalizations and serious outcomes rose over the same period, and a small number of children ended up on ventilators, and two died.

Even setting accidental ingestion aside, the routine use is what concerns me most. Melatonin is a hormone that interacts with the reproductive system. In animals, it appears to play a role in the timing of puberty. We have no long-term studies on what nightly melatonin does to a developing child over years, and we’re giving it to them anyhow in doses that were never designed for a 40-pound body, from bottles that might contain up to three times what the label says. I heard from a growing number of parents over the years who were at their wit’s end about their kids’ sleep and had turned to melatonin because a pediatrician mentioned it, or because it was on the shelf next to the children’s vitamins. I have enormous sympathy for those parents. Sleep deprivation in a family is brutal, and they were doing the best they could with the information they had. But in nearly every one of those cases, when we went back to first principles and worked on the child’s light exposure, screen time, schedule, and stress, we made far more progress than melatonin ever did, and we did it without putting a hormone into a developing body every night.

Kids are, if anything, more responsive to these inputs than adults. Their circadian systems are more sensitive to light, so a tablet in bed or a bright bathroom light before bedtime has an outsized effect, and so does getting them outside in the morning. A consistent bedtime and wake time, including on weekends, does more for a child’s sleep than any supplement I’ve seen. For teenagers whose clocks naturally drift later during puberty, the answer is usually a later schedule and a firm cutoff on screens, not a gummy. If a child has a persistent sleep problem that doesn’t respond to those changes, that’s a reason to look for an underlying cause with a practitioner, not a reason to reach for a higher melatonin dose.

That brings me to what I saw in adults, because it followed a similar pattern. I had many patients who came to me having taken melatonin every night for years, sometimes a decade or more, who still slept badly. If melatonin fixed sleep, they wouldn’t have been in my office. What it had done was mask the problem just enough to keep them from addressing what was driving it. They’d fall asleep a little faster, wake up at three, lie there for two hours, wake up groggy from the dose, and then take more the next night. In almost every one of those cases, we set the melatonin aside and went back to the basics, because again, sleep is downstream of the circadian rhythm and the stress system, and no supplement overrides those two things for long. When we got the timing of light right and calmed down the nervous system, sleep usually improved, typically within a few weeks, and it stayed improved. Melatonin was no longer needed because the body was making its own again, at the right time and in the right amount. A typical case went something like this: Someone would come in who’d been on melatonin for years, having started at a low dose, found it stopped working, and worked their way up. They’d fall asleep fine, but wake at three or four nearly every morning, and they assumed that was just what their sleep was now. We’d taper the melatonin down over a couple of weeks, move their evening lighting to warm lamps and amber glasses, get them outside every morning before they checked their phone, and work on whatever stress was following them to bed. Within a month or so, the early morning wakings would usually settle down.  Most of them weren’t taking anything for sleep by the end, or maybe just a supplement with some herbs or magnesium, which we’ll talk about shortly, and more than one told me they’d forgotten what it felt like to wake up without a fog.

The single most important input, as we discussed earlier, is light, and it works in both directions. In the evening, even ordinary room light is enough to suppress your own melatonin. A study in the Journal of Clinical Endocrinology and Metabolism compared people living in normal indoor lighting before bed to people in dim light and found that room light delayed melatonin onset in 99 percent of participants and cut the total duration of melatonin production by about 90 minutes. That’s the overhead light in your kitchen, not your phone. Screens make it worse, but the room itself is the bigger culprit. Dim the lights after sunset, switch lamps to warm bulbs, put your devices in night mode, and if you’re serious about it, wear amber blue-blocking glasses for the last hour or two before bed. I’ve done this for years, and it’s one of the few things I’m pretty rigid about. Then in the morning, do the opposite. Get outside within the first hour of waking and get bright natural light in your eyes for 10 to 30 minutes. Don’t wear sunglasses for that window, and don’t try to substitute a window indoors because glass filters out a large share of the light your clock is looking for. Even an overcast morning outdoors is many times brighter than any indoor light. That morning exposure sets your clock, and your clock determines when melatonin will rise that night. If you live at a latitude where it’s not light in the morning when you wake up, or it’s just not possible for you to go outside because of your work or routine or schedule, then you might consider a 10,000 lux light panel from Amazon or any number of online retailers. These are typically sold to treat seasonal affective disorder, but they can be effective for this use case as well if you’re not able to go outside.

The second input is consistency. Your body clock runs on predictability. A 2024 study in the journal Sleep followed 60,000 people with wrist-worn trackers and found that how regular your sleep timing was predicted mortality more strongly than how many hours you slept. That’s surprising for most people. People with the most consistent schedules had 20 to 48 percent lower risk of dying from any cause during the follow-up period compared to the least regular group. Going to bed and getting up at roughly the same time, including weekends, is one of the most effective sleep interventions there is, and it doesn’t cost anything.

The third is the stress system. Insomnia is often a state of hyperarousal. The body is in fight-or-flight mode when it should be in rest and digest mode, and no amount of melatonin will talk a nervous system out of that. This is where the wind-down routines, breathing practices, getting the hard conversations and work email out of the last hour of the day, and dealing with the daytime stress that follows you into bed all come in. Cognitive behavioral therapy for insomnia, which is the most effective treatment we have for it, works largely by breaking this arousal loop. You cannot worry your way to better sleep.

Beyond those, the fundamentals still hold. Keep your bedroom cool and dark, and if you can see your hand in front of your face at night, it isn’t dark enough. Even dim light during sleep can disrupt your circadian rhythm. Use blackout shades if your room isn’t naturally that dark. Cut caffeine after noon, and remember that it has a half-life of five or six hours, so a 3 p.m. coffee is still in your system at nine. And for people who metabolize caffeine more slowly, it could still be in your system at midnight or even later than that. Don’t drink alcohol as a sleep aid because it fragments the second half of the night. Finish eating a few hours before bed. And if you snore or wake up gasping, get checked for sleep apnea, because no amount of sleep hygiene will fix a blocked airway.

Supplements come after the basics for most people, not instead of them. But there are two I recommend once the foundations are in place because they support the systems that melatonin is being asked to override. The first is magnesium, which supports normal muscle relaxation and a calm nervous system, and which many people don’t get enough of from food. A 2021 meta-analysis in BMC Complementary Medicine and Therapies pooled three small randomized trials in older adults and found that magnesium shortened the time it took to fall asleep by about 17 minutes compared to placebo. The evidence is modest, and the authors said so, but magnesium is inexpensive, well tolerated, and supports a system you need working rather than substituting for one. That’s why I formulated Bio-Avail Mag with 300 milligrams of buffered magnesium bisglycinate chelate, a form that’s well absorbed and gentle on the digestive system.

The second is a set of herbs and amino acids that support a healthy stress response. L-theanine, saffron, and ashwagandha have each improved sleep quality scores in randomized placebo-controlled trials, and each of them works on the stress side of the equation. Those three, along with holy basil and lemon balm, are what I put into Steady Spirit, which I formulated to support a calm nervous system, because when the stress response settles, sleep tends to follow on its own. Visit AdaptNaturals.com to learn more about each of these products.

If I had to boil all this down, it’s that we’ve taken a hormone and treated it like a vitamin. Melatonin is elegant for what it is, a precise signal that tells your body when night has arrived. Used briefly to reset a clock that’s drifted, it’s a useful tool. Used every night for years, at doses the body never sees, in products that can’t be trusted to contain what they say, it becomes a way of avoiding the harder, more effective work of fixing the conditions that broke your sleep in the first place. So if you or your kids are taking melatonin every night, please don’t feel bad about it. You were told it was harmless, and that’s on the industry, not on you. But I’d encourage you to stop the regular use and give your body the chance to make its own melatonin again, because it knows how as long as it gets the right signals.

Thanks for listening. You can find show notes and links to all the studies I mentioned at ChrisKresser.com. If you have any questions about this episode or suggestions for future topics, head over to ChrisKresser.com/podcastquestion and leave me a message. I read all of them, and your questions help shape the content I create. Until next time, be well.