Quick — tell us everything you know about the pineal gland.
It’s probably not much, right? That’s ok, because until surprisingly recently, scientists didn’t know much either.
But we now know quite a lot, including the pineal gland’s essential function producing melatonin. Dr. Richard Wurtman, Cecil H.Green Distinguished Professor emeritus at the Massachusetts Institute of Technology, talks to us about his work studying the pineal gland and melatonin.
The Third Eye
Your pineal gland is a small endocrine gland in the brain. It was first studied in relation to amphibians (turns out it lightens frog skin) where it’s linked to the parietal eye (also known as the “Third Eye”), which regulates the circadian rhythm based on levels of light in the environment.
But scientists didn’t think it had any function in mammals — considering it an atrophied, vestigial photoreceptor — and certainly nothing to do with melatonin (which was only discovered in the late 1950s).
Eventually, however, Dr. Wurtman and colleagues discovered that if you put animals in constant, bright light, their pineal glands would shrink, and melatonin production would be severely curtailed.
So, it turns out, the pineal gland is still like a third eye, although it’s no longer a photoreceptor, which is why light is first detected by your retina, before that information is passed on to the pineal gland.
High At Night and Low In the Daytime
Once the connection between light and the pineal gland was discovered, it was easy to piece together the role of melatonin.
Environmental levels of lightness and darkness entrain your circadian rhythm, so you sleep when it’s dark and are awake when it’s light. This, in turn, affects melatonin production, so that melatonin is actively produced at night, with very little produced in the day time.
Since levels are high at night, Dr. Wurtman began wondering if melatonin had something to do with sleep onset. Spoiler alert: It did.
Melatonin promotes sleep onset and maintenance, i.e. falling and staying asleep.
Your Aging Pineal Gland
Among other indignities that occur as you age, your pineal gland is calcifying, meaning it’s producing less melatonin at night. This is why older adults have a hard time staying asleep — they produce enough melatonin to fall asleep, but not enough to stay asleep throughout the night.
It’s a pretty easy condition to fix: just supplement with melatonin.
But wait, it’s not that easy. Why? Because the correct dose of melatonin is fairly small (0.3mg) but your body very quickly metabolizes melatonin.
So, if you take 0.3 mg of melatonin before bed, you’ll easily fall asleep, but it won’t be enough to keep you asleep throughout the night.
So just take a much higher dose, right? Nope.
Older adults do need to take melatonin every night, but they’re taking doses that are much too high.
Melatonin is often sold in pills of 3 mg (and even higher), which is 10x the recommended dose (here’s a time-release melatonin pill in the correct dose). The good news is that melatonin is extremely non-toxic, so you’ll never overdose.
But you will blow out your melatonin receptors, so that melatonin supplements stop being effective. When you have so much extra melatonin in your system, your melatonin receptors become desensitized and stop reacting to all that extra melatonin.
Companies are able to sell such high dosage melatonin because the FDA decided to classify melatonin as a dietary supplement, resulting in little oversight.
Dr. Wurtman points out what a mistake this is, since melatonin is clearly a hormone, not a dietary supplement, and no food has ever been found to raise melatonin levels.
The correct dose of melatonin is 0.3 mg. Taking the lowest effective dose will avoid desensitizing your receptors.
Tune into the episode for more on melatonin, plus how different light wavelengths and meal times affect your sleep.
PS: Don’t stay in the dark — sign up for our weekly Brain Breakfast!
Melatonin with Dr. Richard Wurtman
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Discovery of the pineal gland’s function and how melatonin works
Differences in melatonin levels as we age, sleep efficiency, and desensitization
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How does excess melatonin get cleaned out of our systems?
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