It’s Not An Herb . . .
Or even a fancy amino acid, yet it flew off natural food store shelves to the tune of $260 million dollars in 2012. For many, it’s considered a safe alternative to addictive benzodiazepine-based sleeping pills, which have been shown to reduce the amount of deep, restorative sleep you get while simultaneously impairing alertness, coordination and cognition during the day. (source 1, source 2)
I’m talking about melatonin, of course. So what is melatonin, and is melatonin safe? Let’s start with the first half of that question:
Like estrogen, progesterone and testosterone, melatonin is a powerful hormone – the only one that can be legally obtained without a prescription in the United States.1 “While melatonin could be considered natural,” writes sleep expert Dr.Michael J. Breus, “in most cases it doesn’t come from the earth. There are exceptions of foods that contain melatonin in them, but this is a different type of melatonin than what is produced in your brain.” (source)
So what does melatonin do in the body? As I discuss in 18 Science-Backed Tips For Deeper, Longer Sleep, our circadian rhythms – which orchestrate the ebb and flow of cortisol and melatonin – are tied to light and darkness. (source) Cortisol helps us get going in the morning, and melatonin tells our body when it’s time to wind down for bed. Problem is, most of us are out of sync.
While supplementing with melatonin may seem like a good way to get back on track, I personally wouldn’t consider it except for very short-term use. Here’s why:
#1: Supplemental Melatonin May Atrophy The Pineal Gland
Use it or lose it – that’s how the saying goes, right? When it comes to glands that produce hormones that old adage has definitely turned out to be true. By now I’m sure you’ve heard that anabolic steroids – which mimic testosterone – cause testicles to shrink.
That’s because every hormonal system in the body has a feedback loop. “The testicles receive a signal from the brain, in the form of hormones called LH and FSH, that tell them to make testosterone and sperm, as well as grow and develop. If you add a bunch of testosterone (steroids), then these steroids will send a message to your brain saying, ‘Hey, we’re good here, you don’t need to send more signals to make testosterone.’
It’s a negative feedback loop, and over a long period of time this lack of LH and FSH can cause the testicles to just atrophy from lack of activity.It’s kind of like if you had to walk to work every day to make money, but all of a sudden you win the lottery and never have to leave your couch. You still have just as much money, but your muscles will atrophy from lack of use.” (source)
The pineal gland – which produces melatonin – functions the exact same way, says Dr. David Clark. That’s why most melatonin supplements come with a warning not to use them more than 2-3 weeks. Though I have not been able to find any definitive studies on whether pineal gland atrophy is permanent, it appears that in other cases – such as the testes – it sometimes can be.
#2: Melatonin May Affect Fertility
Got baby fever? It may be worth noting, then, that melatonin doesn’t just help set our circadian rhythm – it also helps govern reproductive function. In fact, in Europe high doses of melatonin have been used as a contraceptive. (Source 1, Source 2)
So what exactly is a “high dose”? I wasn’t able to find any numbers, but according to “The Sleep Doctor” Michael J. Breus, many commercially available forms contain three to ten times the dosage determined to be effective by MIT researchers. (Source)
Personally, I think subsequent research on melatonin indicates that it’s probably not “effective” in the way that MIT researchers first thought, but the details are a bit too much to go into here. For our purposes, I think it’s just important to note that individuals are currently self-prescribing melatonin at far higher doses than we have solid research on.
#3: Melatonin May Affect Sexual Development In Children
Though it now comes in cherry flavored chewable capsules, melatonin is not recommended for children by the Mayo Clinic. It “plays a role in the way a person’s body matures sexually,” writes the clinic, noting that melatonin “levels have an impact on how the ovaries and testes function. Further study is needed to determine if taking melatonin during childhood or the teen years can have an impact on a person’s sexual development.”
The National Institutes of Health agrees, saying that “Melatonin should not be used in most children. It is possibly unsafe. Because of its effects on other hormones, melatonin might interfere with development.” (Source)
In other words, we have no idea yet how supplementing this hormone in children might affect their development.
#4: Other Possible Side Effects
According to the Mayo Clinic, melatonin supplementation can also cause daytime sleepiness, dizziness, headaches, abdominal pain, mild anxiety, irritability, confusion and feelings of depression. (Source) In rats, high melatonin levels have also been shown to decrease T3 & T4 (thyroid hormone) uptake. (Source)