Most Replayed Moment: Sleep Expert On The Truth About Melatonin And Magnesium

**Steven Bartlett** (0:00)
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Are you concerned that melatonin is becoming more and more popular as a way to solve lifestyle issues that have caused sleep impairment? Because I'm seeing loads of, you know, I'm an investor, so I see lots of companies now pitching me different products that have melatonin in them as a sort of day-to-day sleeping supplement.

**Matthew Walker** (1:23)
I think I'm really torn. I've been on both sides of this argument, and I'm cautious about it for two reasons. The first is in pediatric populations here in the United States.

**Steven Bartlett** (1:34)
Pediatric?

**Matthew Walker** (1:35)
Yeah. So the people's use of melatonin in kids is increasing. So in pediatric populations, it's increasing exponentially. In fact, if you go down the sort of the supermarket aisles here in America, often if you go into sort of the health sort of food section, there's this big purple section, that's the melatonin section. And a large proportion of that is they're dedicated to gummies for your children with melatonin. And there was a study that was published about three years ago that showed here in America over the past 10 years, there has been a 503% increase in poisonous overdose admissions to hospitals of melatonin in the past 10 years. 503% increase.
So firstly, we've got to be a bit careful. The second reason is that melatonin is a bioactive hormone, and it's also involved in reproductive development. And there were studies done back in the 1970s, I think, where they were looking at juvenile male rats, which is to say, male rats who were going through adolescence.
And they were dosing them with high amounts of melatonin. And what they found is that that stunted the development of the testes, of the testicles, and it caused testicular atrophy. Now, these were very high doses. But we've got to be a little bit careful. We think, we say, well, melatonin is a natural hormone, so anything natural is safe. Melatonin overall, in terms of its safety profile, is very safe. It's actually a very good antioxidant. But you've got to be careful, because things like, for example, testosterone supplementation in males, what we know is that if you're injecting testosterone, after a while, after maybe 18 months or so, the testicles themselves will stop producing their own testosterone. And even if you stop the administration of the exogenous testosterone, the injection, the testes never return their function of producing testosterone. Now, we don't have any evidence yet that that's the case, that if you keep taking melatonin at high dose, your body, the fear would be, shuts down its own natural production of melatonin. I've seen no evidence of that. In fact, I've seen evidence, the contrary, that even after about six months or even 12 months in certain small cities, when you stop melatonin, the production starts again naturally. It seems fine. Problem is, people haven't been taking melatonin for just 12 months. They've been taking it for years.
We've got no idea what happens after years.

**Steven Bartlett** (4:09)
That was my hesitation when the first time someone offered me melatonin is, from doing this podcast and speaking to smart people like yourself, I've come to learn this principle that if you start making something for your body in terms of a hormone, if you start consuming something externally like testosterone, your body will say, fine, I don't need to do this. It will try and return to that level of balance where the quantities in your system are maintained, which means it learns to shut down. I always think about the case of testosterone, because men know that if we start injecting testosterone, then we're going to have to pretty much do it forever. If we want those levels to be the same.