41. The Pineal Gland & Melatonin | Descartes, Darkness & How the Body Keeps Time

In this episode of Mohivate, Dr Mohi Sarawgee explores the pineal gland and melatonin, and the ancient system that tells every cell in your body what time it is.

In the 17th century, René Descartes pointed to a single structure buried at the centre of the head, a gland the size of a grain of rice, and called it the seat of the soul. For four hundred years, this tiny gland has drifted between mysticism and medicine. It has been linked to the third eye, to spiritual vision, to “brain sand,” and, more recently, to some genuinely serious neuroscience.

But what is the pineal gland actually doing in there? And why is the hormone it makes, melatonin, so much more than the sleeping pill most of us believe it to be?

From an organ that was once, in our evolutionary past, a literal light-sensing eye, to the darkness signal that governs your sleep, your ageing, your immune system, and even your gut, we follow melatonin’s extraordinary reach across the whole body. We explore why you wake at three in the morning, what blue light really does to your biology, why melatonin sits at the centre of research into Alzheimer’s and cancer, the truth about “decalcifying” the pineal gland, and the honest facts about the supplements sold online.

With clinical insight, a little history, and a personal thread that runs through meditation and stillness, this is an episode about the small gland that keeps time for all of us, and what it means to let the body remember a rhythm it has known for millions of years.

References: 

1. IARC Monographs Vol 124 Group (2019). Carcinogenicity of night shift work. The Lancet Oncology, 20(8), 1058–1059. Night-shift work classified by the WHO/IARC as a probable cause of cancer (Group 2A).

https://doi.org/10.1016/S1470-2045(19)30455-3

2. International Agency for Research on Cancer (2020). IARC Monographs Volume 124: NightShift Work. World Health Organization. The official WHO/IARC source; lists breast, prostate, colon and rectal cancers.

https://www.iarc.who.int/news-events/iarc-monographs-volume-124-night-shift-work/

3. Rhythms of life: melatonin, nutrition, sleep, and antioxidant strategies for healthy aging. Frontiers in Neuroscience, 20:1736978.

https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2026.1736978/full

4. The melatonin–microbiome axis: a new frontier in gut health (2025). Inflammopharmacology.

https://link.springer.com/article/10.1007/s10787-025-02005-4

5. Microbial melatonin metabolism in the human intestine as a therapeutic target for dysbiosis andrhythm disorders (2024). The gut producing far more melatonin than the pineal gland; gut–microbiome interaction.

https://www.nature.com/articles/s41522-024-00605-6

6. Hardeland, R. (2015). Melatonin and brain inflammaging. Progress in Neurobiology.Melatonin declining with age, lower in Alzheimer’s, and its role against brain inflammation.

https://pubmed.ncbi.nlm.nih.gov/25697044/

7. Melatonin as an Anti-Aging Therapy for Age-Related Cardiovascular and Neurodegenerative Diseases (2022). Frontiers in Aging Neuroscience.

https://pmc.ncbi.nlm.nih.gov/articles/PMC9204094/

Just a gentle reminder: this episode is for information, education, and inspiration only. It’s not a substitute for your doctor’s advice. For any personal health concerns, always seek guidance from your doctor.

Transcript

SPEAKER_00 0:08

Hi everyone, welcome back to Mohivet. I'm Dr. Mohi Saraugi, a GP by profession, but here I'm swapping prescriptions for perspective. I want to start today with a man sitting alone with a question he was almost too afraid to answer out loud. The man is René Descartes, one of the greatest philosophers of the 17th century. The man who gave us, I think, therefore I am. And he was wrestling with one of the oldest questions human beings have ever asked. Where in the body does the soul live? Where is the meeting point between the physical thing that is you and the part of you that thinks and feels and knows that it exists? After years of dissection, Descartes settled on one answer. He pointed to a single structure buried right at the center of the head, an organ shaped like a pine cone about the size of a grain of rice. That structure is called the penial gland, and Descartes said that there, in that tiny gland, lies the seat of the soul. His reasoning was rather beautiful. He noticed that almost everything in the brain comes in pairs. Two hemispheres, two eyes, a matching right and left for nearly everything. But this little structure, the penial gland, was singular. One of it alone at the center. And to Descartes, that felt right. One soul, one consciousness, one gland to hold it. He was so wary of what the church would make of this that he sat on the idea for years. It was finally published in 1664, 14 years after he had died, and almost immediately the great minds of the age lined up to tear the idea apart. And yet, the idea would not die. 200 years later, in 1888, a mystic named Helena Blavatsky connected the penial gland to the third eye, the seat of inner vision. In the 1920s, another thinker, Rudolf Steiner, looked at the little grains of calcium that build up inside the penial gland as we age and decided they were spiritual potential crystallizing. He called them brain sand. And today, nearly 400 years after Descartes, this tiny structure is still argued over, still at the center of both meditation retreats and some genuinely serious neuroscience. So here's the question I want to discuss with you today. What did Descartes actually find? Because science did eventually open this gland up and it did not find a soul, at least not yet. It found something almost stranger. It found a clock, a tiny ancient timekeeper that reads the darkness and tells every cell in your body what time it is. And that clock makes a single hormone, one now sold in many countries beyond the UK, on Amazon, on eBay, and even TEMU in doses a hundred times higher than anything your body would ever make on its own. That hormone is melatonin. Most of us think of melatonin as a sleeping pill when it's really something closer to a message. It's a darkness signal, a master regulator of your body clock that quietly reaches into far more of the body than anyone expected. And underneath all of it sits a question I find genuinely difficult to let go of. One I've been sitting with personally in stillness for some time now because these days I do a fair bit of penial plan meditation myself, and I've seen some genuinely beautiful results from it. So this next part is a little bit for me as much as for you. The question is this was Descartes entirely wrong, or was he pointing clumsily with the wrong language at something real? He may have got the mechanism wrong, and science still has a great deal to prove here. But I'm no longer quite so sure he was wrong to look here. So today let's talk about the pineal gland and melatonin and why it's something more than just the thing that helps you sleep. So let's begin. Let's start with the gland itself. The pineal gland sits deep in the center of the brain, tucked between the right and left hemispheres. It's roughly the size of a grain of rice, weighing less than a fifth of a gram, and it's shaped like a tiny pine cone, which is exactly where its name comes from. From the Latin pinia for pine. Descartes was struck by the fact that it stands alone without a twin on the other side. But there's a second thing that makes it unusual, and this one matters more. Most of the brain is sealed off behind something called the blood-brain barrier. Think of it like a security filter that decides what's allowed to cross from the bloodstream into brain tissue. It keeps the brain protected and separate. The penial gland sits outside that barrier. It stays in direct contact with what's flowing through the blood, almost as though it's designed to keep reading the state of the body and the state of the world from moment to moment. And what it's reading for primarily is light or rather the absence of it. Now, here's the detail I find genuinely beautiful. In some fish and reptiles, the penial gland isn't buried in the brain at all. It sits just beneath the top of the skull under a patch of thin, almost transparent tissue, and it detects light directly. In those animals, it works in a real biological sense as a third eye on the top of the head. In humans, over the course of evolution, the penial gland moved inward, deep into the center of the brain, but it never lost its fundamental light sensitivity. It is still, in a real sense, an eye, an internalized one that now reads the body's chemistry rather than the light itself. So when the spiritual traditions of the world speak of the third eye, the Agnya chakra in the Hindu tradition echoed across many separate cultures. They are describing in their own language an organ that genuinely does have the biological history of being an eye. That convergence is worth pausing on. And don't worry, this episode is not about belief. It's about science, what we know, what we don't know yet, and why I think some of the questions this little gland raises deserve to be taken far more seriously than they have been. At heart, the penial gland is a timekeeper. It reads light and darkness and turns that reading into a chemical message the rest of the body can understand. When light hits the retina, a signal travels to a small cluster of cells called the suprachiasmatic nucleus, the body's master clock. In daylight, that master clock leans over to the pineal gland and says, Not yet, the sun is still up, stay quiet. So the gland waits. Then darkness falls, the signal lifts, and the master clock finally gives the nod, and the pineal gland begins releasing its hormone into the bloodstream. That hormone is melatonin. As far as the science is concerned, this is the pineal gland's core job. It is a biological darkness detector, and melatonin is how that message reaches every cell in your body, telling all of them at once what time it is. There's one last thing worth mentioning because it comes back later. As we age, the pineal gland slowly begins to calcify. Small deposits of calcium build up inside it. The very grains that Rudolf Steiner romantically called grain sand. It starts earlier than you think, often in adolescence, and by the time most of us reach our 70s, the gland is noticeably calcified. What that actually means for how it works is still not fully understood. And given everything else about this strange little structure, that feels about right. Now let's talk about the melatonin hormone itself. Melatonin starts life as something completely different. It begins with tryptophan, an amino acid you get from food. Tryptophan gets converted into serotonin, the same molecule that helps keep your mood steady through the day. And then when darkness falls, the penial gland takes that serotonin and in one more step converts it into melatonin. So the very molecule that keeps you calm and stable in the daylight becomes at night the signal that tells your body the day is over. Now, melatonin is not a sedative. It won't put you to sleep the way a sleeping tablet does. What it does is send a message. Night has begun. Sleep is one thing that follows, but only one. That same signal also begins a whole night shift of work. Immune activity, cellular repair, a cascade of hormonal changes. Melatonin does not command any of it. It simply announces that the time has come. In a healthy adult, melatonin rises through the evening and peaks somewhere between 2 and 4 in the morning. That's the body's deepest biological night. The point where melatonin is highest, your body temperature is at its lowest, and repair is running at full tilt. This is why sleeping on time is so purposeful. It's the unseen maintenance window your whole night is built around. And it's exactly why so many people ask me the same question. Why do I keep waking up at 3 in the morning? Hold that thought. Because melatonin has a partner in all of this. And we'll come back to that a little later. Now, if melatonin only told the time, that would already be remarkable enough. But it turns out melatonin is one of the most powerful antioxidants in the human body. Every cell in your body burns fuel to make energy. Mostly sugar from the food you eat burned with the oxygen you breathe. And just like anything that burns, it produces a kind of exhaust. Unstable little molecules that bump around inside the cell and cause damage. Scientists call them free radicals. Think of them like tiny sparks flying off a fire. A few are harmless, but over a lifetime, all those sparks scorching away at your cells are part of how we age and part of how disease gets a foothold. Melatonin is one of the best defenses your body has. What makes it special is where it can reach. It slips right inside the mitochondria, the tiny powerhouses inside every cell where most of those sparks are thrown off in the first place. So it puts the fire out right where it starts. And it does something cleverer still. It also wakes up your body's own natural defenses and tells them to get to work. Melatonin is also closely tied to your immune system. At night, while melatonin is high, it helps your immune defenses do their housekeeping, calming down unnecessary inflammation and keeping the whole system balanced rather than overfiring. And inflammation, very simply, is the body's response to threat. Helpful in short bursts, like when you cut yourself and the skin goes red and warm, but harmful when it smolders on quietly for years. That slow, constant kind, the kind that comes with chronic stress, poor sleep, and aging is exactly what melatonin helps hold in check. And you can see what happens when this rhythm is broken. Think of shift workers, doctors, nurses, pilots, police, factory and call center workers, people whose bodies are told it's night when it's really day, night after night, for years. Their melatonin never comes at the right time. So all that overnight repair keeps getting interrupted and the research shows it leaves a mark. Shift workers have measurably higher rates of certain illnesses, including some immune-related conditions. When the message of darkness stops arriving on time, the body slowly loses its nightly chance to put itself back in order. So melatonin is a timekeeper, an antioxidant, and an immune protector. Three jobs from one small molecule, all flowing from that single original purpose. It reads the darkness and it prepares the body for night. Now something genuinely unusual. The penial gland is not the primary source of melatonin in the human body. The gut is. The GI tract produces approximately 400 times more melatonin than the penial gland. And this gut melatonin plays by completely different rules. It mostly ignores the clock. It is produced locally in response to food, the conditions in your gut, and the makeup of your microbiome. And it acts locally to setting the pace that moves food through you, supporting the gut's own immune defenses, protecting the gut lining, and helping keep the microbiome itself diverse and balanced. The relationship between melatonin and the gut microbiome is now one of the most active research areas in this whole field. A very recent 2025 review described what researchers are calling the melatonin microbiome axis, a two-way relationship between the melatonin in your gut and the bacteria that live there. A healthy population of gut bacteria helps your body make melatonin from the food you eat, and in turn, healthy melatonin levels help keep that bacterial community balanced and diverse. They prop each other up, and when either side breaks down through chronic stress, broken sleep, heavily processed foods or repeated causes of antibiotics, the other tends to fall with it. They go down together. Low-cut melatonin is now being linked to what you may have heard called leaky gut, which means the gut lining grows more permeable, and that's linked to higher inflammation across the whole body, and your gut is in constant conversation with your brain along the vagus nerve. The brain gut axis I've talked about here before. So, what happens to melatonin down in your gut can ripple all the way up into inflammation, into mood, into how the whole body feels. So the next time someone tells you to trust your gut, it turns out there's more wisdom in that than they knew. Your gut is quietly making the very molecule that helps keep it calm, protected, and in balance, which is really just one more reason that how you feed it matters more than most of us were ever taught. For almost our entire history, melatonin had a simple life. The sun went down and the penial gland went to work. The sun came up and it switched off. Our nights were genuinely dark and the signal was clean. The body always knew what time it was. And then we lit up the night. First came electric light, which let us push our evenings later and later. Then came the phone in your hand and the laptop on your knee, giving off a particular kind of light, blue light. And blue light happens to be the exact signal your body reads as daytime, the wavelength of a bright midday sky. So when you're lying in bed at night, doom scrolling, then as far as your penial gland is concerned, you're sunbathing. And the effect is not small. Studies have found that a bright screen late in the evening can suppress your melatonin by as much as 50%. You're telling a gland that has spent millions of years learning to read the darkness that the sun is still high in the sky and it believes you. So it holds the melatonin back, and you lie there wondering why you feel tired, but somehow can't quite fall asleep. And this matters far more than a lost hour of sleep. Push melatonin later, night after night, year after year, and we disrupt that whole night shift of repair and antioxidant defense. Large studies now link this kind of long-term body clock disruption to a serious list. Higher rates of weight gain tied to diabetes, heart disease, and depression. The sleep you lose is only the surface. Underneath it is a body that can no longer properly tell what time it is. And here's the part I love because it costs nothing and it's completely in your hands. The answer isn't a supplement or a gadget, it's darkness. Warm, dim light in the evening, the soft yellow orange of lamp light or candlelight barely disturbs melatonin at all. It's the bright blue screen and ceiling light that does the damage. So in the last hour before bed, dim your lights, warm their colour, and put the phone down. These are the closest things we have to giving your body back the honest darkness it evolved to expect, and your penial gland will do the rest. Now, melatonin doesn't stay steady across your life. It falls and it falls a lot. An average 70-year-old makes only about a tenth of the melatonin they made at 20. As we get older, we slowly lose the very hormone that's been quietly protecting us all along. And there's something rather poignant in that. And that decline lines up closely with something researchers now call inflammaging, the low, constant background inflammation that builds up as we age and that sits underneath so many of the diseases of later life. A 2026 paper described melatonin as a kind of central signal, tying together our body clock, our sleep, and our antioxidant defenses. And as melatonin falls, all three weaken together. The clock drifts, sleep frays, and the cell's protection thins out. The link to brain disease is where this gets genuinely striking. In the lab, melatonin has shown protective effects against Alzheimer's, Parkinson's, and multiple sclerosis. And in Alzheimer's, especially the processes melatonin normally holds in check, the buildup of harmful proteins, oxidative damage, inflammation in the brain are the very processes that drive the disease forward. Melatonin levels are consistently lower in people with Alzheimer's than in others their age, and that drop often shows up years before the memory symptoms do. Now I want to be careful here because this is exactly the kind of finding that gets oversold. None of this means melatonin supplements prevent Alzheimer's. We do not have the human trial data to say anything like that, and anyone who tells you otherwise is getting ahead of the science. What it does mean is that this hormone keeps turning up again and again at the center of how the brain ages, and that's why the research world is watching it so closely. Then there's cancer. The WHO classifies night shift work as a probable cause of cancer, and the leading explanation is exactly that chronic suppression of melatonin over a working life spent against the body's rhythm. Melatonin is now being studied in cancer care itself with dozens of trials underway, some looking at whether it can ease the exhaustion and low mood of patients going through treatment. So the pattern across all of it, aging, brain disease, cancer, keeps pointing back to the same place. A molecule that sits right at the crossroads of light, time, repair, and protection. And when it fades, a surprising amount seems to fade with it. Now let me keep that promise. The 3 a.m. in the morning wake up. Melatonin has a partner and in some ways an opposite. It's cortisol, your main stress hormone. The two work like a seesaw. Through the night, as melatonin does its quiet work, cortisol stays low, bottoming out around midnight. Then, through the second half of the night, cortisol slowly begins to climb, gently lifting you toward waking. That rise is your body preparing you for the day. That's how it's meant to go. But when you're under real ongoing stress, cortisol doesn't wait for morning. It runs high and it starts climbing too early, breaking through in the small hours while you're still supposed to be asleep. And that's the moment it pulls you awake, often around the same time each night. Mind switched on, thoughts already racing, and no obvious reason for it. If that's you, please remember this. A healthy night of melatonin helps keep cortisol in check. So when melatonin is planted by stress, by light, or by age, that overnight calming weakens too, and you can wake already running at a higher baseline than you should. It works as a loop. But the good news about loops is that they can be turned in the other direction. And one of the oldest ways humans have found to turn that loop around is simply to sit still. Now I want to bring this back to the pineal gland and to that pineal gland meditation I mentioned at the start. To explain why that matters, I need to bring you back to the default mode network. Something we discussed in our psilocybin and magic mushrooms episode. It's a set of brain regions that switch on when you're not focused on anything in particular. When your mind wanders, replays the past, rehearses the future, running that endless inner commentary about yourself. Think of it as a voice in your head. We all need it. But when it runs too hot, it's closely tied to rumination, anxiety, depression, and that stuck feeling of being trapped in your own thoughts. It's a lot of what we mean by an overactive mind. In experienced meditators, the default mode network is measurably quieter, not just while they meditate, but as their normal resting state. The voice in the head turns down. Psychedelics like psilocybin seem to do something remarkably similar, quietening that same network, loosening the grip of the self-focused narrator. So you have two very different doors: deep meditation on one side, these compounds on the other opening into the same room. Contemplative traditions have described that room for thousands of years. Neuroscience is only now starting to map it. And this is where the penial gland quietly re-enters the story, sitting in the same family of molecules as melatonin, the tryptamines, all built from the same amino acid. Tryptophan is a compound called dimethyltryptamine or DMT. It's a powerful psychedelic and remarkably the body makes small amounts itself. For years, people have wondered whether the penal gland might be involved. Let me be honest about where the sign stands. Yes, the body produces DMT, but the popular claim that the penal gland floods the brain with it during deep meditation or birth or death is not yet established. The amounts appear far too small, and the evidence simply isn't there yet. So I'm not going to tell you that meditation is a DMT experience. What I'll say is more careful and I think more interesting. Something real happens in these deep states. It's measurable. We don't yet fully understand it. And that's not a reason to dismiss it. It's a reason to stay curious because what the evidence does show is remarkable enough on its own. Sit quietly and return your attention to the present again and again over time, and the ruminating self-referential network in your brain grows quieter, the voice settles, and that to me is the real beauty of it. You come back in the most literal, measurable sense to yourself. Now, remember those little grains of calcium, the brain sand that build up as we age? Here's what we actually know the penial gland does calcify over time, and in some studies, more heavily calcified glands are linked with lower melatonin. What isn't established is the dramatic version, the idea that a calcified pineal gland is a blocked third eye, switching off your intuition or your spiritual capacity, and that a special diet or supplement can decalcify it and switch it back on. That part is not supported by evidence. The calcification is real. The decalcification products being sold to reverse it are not doing what they claim. Now, those melatonin supplements sold online. Your body's own melatonin peak at its highest point in the night is only about a tenth to three tenths of a milligram, a fraction of a milligram. Now look at what's sold. Here in the UK, the lowest prescription tablet is 2 mg, but in countries where it's sold freely, the common supplements are 5 or 10 milligrams, and investigators this year found products on sale at 30 milligrams. That's up to 100 times more than your body would ever make on its own. And more is not better. The research is fairly consistent that low doses work just as well as the big ones for helping you settle into sleep with fewer next day effects. In fact, push the dose too high and the melatonin can still be circulating the next morning, which is part of why people wake up groggy. You end up blunting the very system you're trying to help. There's a quality problem too. When researchers tested a batch of these supplements, the actual amount inside ranged from far less than the label claimed to far more, and some contain serotonin, a different hormone entirely unlisted on the packaging. When it isn't tightly regulated, you often don't truly know what you're taking. And perhaps that's why here in the UK, melatonin is a prescription-only medicine. The licensed product is even modified release designed to drip out slowly through the night the way your own melatonin would, rather than arriving as one big hit. As a GP, I can prescribe it for the right person at the right dose as a properly regulated product. And I gently say that the regulation, which frustrates a lot of people, is also protecting them. So does melatonin ever genuinely help? Yes, in specific situations. The strongest case is jet lag, taken at bedtime in your new time zone. It helps nudge your body clock to catch up faster. It also helps people whose natural sleep timing has drifted very late, and there's reasonable evidence in adults over 55 whose own melatonin has declined, and in some children with neurodevelopmental conditions where it started under specialist care. But notice the theme: in every one of those, melatonin is working as a timing signal. Resetting a clock that's out of step. What it doesn't do is knock out an otherwise healthy person who simply can't sleep because they are stressed, wired, or scrolling in a bright room at midnight. For that, melatonin is the wrong tool, and the right ones are what we'll come to now. So, what should you actually do? The good news is that the most powerful things are simple, free, and entirely in your hands. The first is light. Get bright light early in the day, ideally within an hour of waking, and it resets your body clock. Then in the evening, do the opposite. Dim the lights in the evening. Warm color screens down. You've heard me say it, it matters that much. The second is darkness while you sleep. Even small amounts of light in the room can dent melatonin. So make your bedroom as dark as you comfortably can. The third is rhythm. Your body runs on a clock, and clocks like consistency. Going to bed and waking at roughly the same time most days does more than almost anything else. And that includes meal timing too, which your gut clock reads just as closely. If your work shifts, and I know many of you do, the reality is harder as you're working against your biology. But a few things genuinely help. Keep your bedroom as dark as possible when you sleep in the day. Protect your sleep window fiercely, even when the world is awake, and get bright light during your working night so your body has some signal to hold on to. You can't fully solve shift work, but you can soften its edges. And if you're going to use melatonin, use it as the timing signal it is. A low dose taken a little before your intended sleep time is closer to how your body actually works than the large doses on the shelf. And if sleep is a real, ongoing struggle, please speak to your doctor rather than reaching for stronger and stronger tablets online. Very often, the real issue is stress or light or rhythm, and those are the things that actually move the needle. So here we are. Perhaps Descartes never really found the seat of the soul, but I think he found something that reminds us how extraordinary the human body really is. A tiny gland quietly reading the darkness, keeping time for every cell we have, protecting us while we sleep, and asking for remarkably little in return. A little daylight, a little darkness, a little rhythm. There's no supplement here, nothing to buy, nothing to force. And maybe that's the real lesson of this tiny gland. So much of health turns out to be quieter than we are told. It's letting the darkness fall when it should, letting the morning light in, and letting the mind grow still enough now and then to hear itself again. Your body already knows what time it is. The only real question is whether we let it remember. I hope something today stirred a thought, gave you a smile, or simply made you pause. Thank you for listening. I'm Dr. Mohi. Until next time, remember this. When the world gets a little too loud, try trusting the wisdom of your own biology. It has been quietly looking after you for a very long time, and listening to it is one of the most beautiful ways I know of finding our way back home to ourselves.