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Erin Flynn-Evans PhD MPH
Apr 29

Melatonin is a Hormone

Updated and revised from an earlier version based on new science.

Dark sky

We’ve been hearing a LOT about parents experimenting with melatonin lately and we feel that it’s important that you know the facts about melatonin before you consider giving it to your child. Since we originally wrote this blog, sales of melatonin have more than doubled and calls to poison control regarding accidental melatonin ingestion have increased 530%. We hope this blog helps you understand why you should think twice before giving your child melatonin.

There are probably hundreds of blogs out there proclaiming the wonders of melatonin. When you read these articles, please pay careful attention to who wrote the articles and who is funding the post. At Baby Sleep Science we strive to offer balanced opinions and advice on every topic, but on the topic of melatonin, we certainly have a position.

But before we get to that, it’s important that you understand where we are coming from — Dr. Flynn-Evans is the scientific grandchild of the woman who literally wrote the book on melatonin (seriously, it’s called “Melatonin” and was written by Dr. Josephine Arendt). Dr. Flynn-Evans' Ph.D. dissertation has a 20-page summary of the history of human melatonin production and the effects of melatonin administration. Dr. Flynn-Evans measures melatonin in virtually every study that she runs in her lab. At Baby Sleep Science we are all passionate about the topic, but we hope that you will agree that it’s because we know what we are talking about!

The Science

Melatonin is a hormone. It is produced in the pineal gland of the brain and on average people produce about 0.3 mg of melatonin a day, but there is a good deal of variation in the amount of melatonin produced between individuals. A person whose body produces more melatonin does not necessarily sleep better than someone who produces less melatonin. Melatonin is passed through breastmilk and nursing helps newborn mammals of many species adapt to the 24-hour day (the jury is still out on whether humans work this way). Many sleep researchers refer to melatonin as the “hormone of darkness,” because if you stay awake all night in the dark, then your body will still produce melatonin. If you turn on a light at night, then your body will immediately stop producing melatonin.

Why should you avoid giving melatonin to your child?

Although there are many reasons, here are an important few:


1. Melatonin doesn’t make you sleep — it changes the timing of your sleep.

When you take melatonin as a drug, it is referred to as a chrono-hypnotic (sometimes chronobiotic). “Chrono” refers to time and “hypnotic” refers to sleep, this is because taking melatonin does not make you sleep per se, it just changes the timing of your circadian rhythm. This means that your drive to sleep will be shifted earlier, but it doesn’t mean that you or your child will sleep longer. Practically, you may end up with an earlier bedtime, but not necessarily a more well-rested child. In fact, your child’s body clock would shift earlier, leading to an early wake time.

2. Melatonin tablets are generally more than 10 or more times what your body produces.

As described above, melatonin does not make you sleep. As noted above, our bodies naturally produce ~0.3 mg of melatonin, but most melatonin tablets are labeled as 5 mg. Unlike other drugs, more melatonin does not lead to a bigger effect. More melatonin might actually cause a longer melatonin pulse, making it harder to figure out when your sleep drive is happening in the future.

3. Melatonin is unregulated in the United States.

Although most people think that over-the-counter substances are safe, the truth is that the tablets that you can buy in grocery stores and natural food stores are unregulated by the FDA. This means that you have to trust that the manufacturer has taken care to assure that the dose in the tablets is accurate. Unfortunately, a few researchers have tackled this issue and found that there is wide variation in the dose of melatonin that you actually get in a pill. This means that you might buy a 5 mg tablet, but some of the pills will have 0 mg and some will have 20 mg. In addition, some studies have found that the tablets contain other supplements or filler like valerian root, St. John’s wart, and even CBD!

4. Melatonin is the cue for the breeding season in animals.

So far you might be thinking, “okay, okay, I hear you but I like my more peaceful bedtimes since starting melatonin with my child and I trust my supplier/brand of vitamins.” Perhaps these next two items will change your mind. As described above, when you are exposed to light, the melatonin signal turns off. When you are exposed to darkness the melatonin signal turns on. This is how seasonally breeding mammals are able to tell when to mate — melatonin is a seasonal timekeeper. In sheep, short days/long nights are the cue for melatonin to turn on the reproductive hormones and stimulate breeding. Something similar happens in hamsters and horses, which are long-day breeders. So, how does this relate to humans? We don’t know. Humans are exposed to so much artificial light that it’s hard to determine whether there is a seasonality to our breeding patterns (some old studies suggest there is such a pattern with a spring peak, but there isn’t a scientific consensus either way). There are melatonin receptors all over the human body, including in the testes and ovaries, but we don’t really know how melatonin interacts with human reproductive hormones.

5. Melatonin was once developed as a human contraceptive.

Although it never came to be an approved form of human birth control, the fact that it showed promise in this role will probably make you think twice about giving it to your children.

6. Overconsumption of melatonin has led to death.

No parent would ever deliberately give their child an extreme dose of melatonin but because so many melatonin supplements are packaged as gummies, many children have gotten into their parents' supply and ended up in the hospital. There have been at least two cases of children dying after consuming melatonin.


Should I give my child foods to enhance melatonin?

We’ve heard that some parents are giving their kids cherry juice and other foods to “increase melatonin production.” We did a quick literature review on these studies and while these foods may increase precursors to melatonin, the cherry studies were all funded by the cherry industry. We’d like to see some neutral studies on the topic. But, once again, even if cherry juice or other dietary changes did lead to an increase in melatonin production it wouldn’t lead to increased sleep and it would lead to a lot of extra sugar! So, we think it’s better to stick to great sleep hygiene, regular age-appropriate schedules, and proven behavioral interventions to help your child sleep well in the long run.

Is there EVER a time to consider giving my child melatonin?

Melatonin may be helpful for regulating sleep in children who have circadian rhythm sleep disorders, such as in children who are totally blind. There is some limited research to support the use of melatonin in children with autism as well. In each of these cases, you should work with your child’s pediatrician to create a treatment plan and obtain a prescription for pure melatonin from a pharmacy.

 

References and Further Reading

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