I have no idea how many lectures and symposiums I’ve done, how many emails, tweets, and direct messages I’ve answered, but I would guess that about 15% of all the questions that I get are around this very question. Don’t get me wrong, there is a lot of variations to how the questions get asked, and lots of nuances with each person, . I still reserve the right to be wrong, but I’ve been discussing this and reading about it for about 7 years now, and I’d be really surprised if I’m terribly wrong on any of this.
Remember when I said I reserve the right to be wrong? That’s because I’ve been wrong before. Hopefully, I haven’t destroyed your faith in my expertise? However, for years I said: “Taking exogenous melatonin will decrease your brain’s natural production”. There is still a chance I’m right here, but, so far, no research has borne this to be true. However, I haven’t read any studies where they actually measured the melatonin levels inside a human’s brain. If any of you know of such a publication, please email it to me. What they have done is give people melatonin supplements and then measured the salivary quantities of melatonin over time. Obviously, I’m an MD and not a Ph.D. in neuroanatomy and neurophysiology, so I can’t say if that is a valid test or not. Obviously, saliva doesn’t come from your brain.
So, I’m not sticking to my guns here to be obstinate or vindicated later. I’m just going to apply some country-boy turned doctor logic. Melatonin is a hormone. We have hundreds of hormones, and hundreds more, if not thousands, of other intermediates that have hormone-like effects. Here’s where I get a pretty good foundation to postulate because I did learn a lot about hormones in medical school and post-graduate training. Our bodies are about 600 million times more complex than we like to pretend because, at the end of the day, we’d have to admit that we know almost nothing about how all of these thousands of hormones, and pro-hormones, and pre-cursors, etc. behave during different times of the day, how they interact with each other, how they act in different tissues (the same hormone can have a completely opposite effect in two different tissues).
But, we do know this. If I give you hormones (pills, patches, creams, injections) to put into your body “exogenous”, and the amount I give you is as much or more than your body needs, your super-smart, super-efficient, super-evolved body will severely diminish or completely stop making that hormone. Why, because it’s already there. If I delivered groceries to your house every day, would you still go to the grocery store? So, if this does not happen with melatonin, it is the ONLY hormone that I am aware of which behaves this way.
Nonetheless, even if melatonin is this magic hormone that always gets produced, we still have another problem: receptors. Almost everything floating around in our blood that eventually gets into cells has some sort of receptor involved. The details are beyond the scope of this blog, but think of the thing floating around in our blood as a baseball, and the receptor is a baseball mitten. The ball fits in the glove, the glove says come with me and escorts the ball to some other place to do whatever that kind of baseball does to whatever kind of cell we are talking about. Now, if a cell only needs one baseball per day, and there are millions of baseballs floating around, how many mittens do you need? Not very many rights? But, what if the cell needs 500 baseballs per day, and you’re entire bloodstream only has about 1000 baseballs per day floating around. That cell would be covered in receptors right?
So, here is the point; if you take exogenous melatonin every day, and that amount of melatonin is way more than your body needs, you will decrease the number of melatonin receptors. Research has supported this—in many tissues. If you then quit taking these high doses of melatonin, you will have so few receptors that your body’s cells will perceive a deficiency of melatonin. This really makes no difference if you have low melatonin production or inadequate receptors. The end result is your cells won’t get what they need, and unlike many other hormones your brain does not have the ability to drastically increase production—as nearly all melatonin in your brain is made between sundown (or lights out) and sunup (or lights back on).
So, if you’re completely bored with this by now, fear not: it’s almost over. If you want to take 1-3mg of melatonin for a few days around jet lag or something like that—no problem. Taking more than your body needs for a few days will not down-regulate receptors and likely will not affect production. However, if you are taking it on a regular basis (presumably to help initiate sleep), I would recommend extraordinarily low doses (2-4 micrograms), and not “time-released”. After you have initiated sleep, you want your brain to keep the cycles going to get a good night of sleep.
I will close by saying that I have read The Melatonin Miracle (some years ago), and you might be rightfully screaming at me that melatonin does more than help with sleep, and you are correct. Melatonin has a host of other effects and is a great anti-oxidant. However, I will leave you to your own research and prioritizations in taking melatonin for other suspected benefits.