Supplementary melatonin is the fourth most popular natural product used by adults in the United States and the second most popular natural product given to children. It can change the timing of sleep, ease jet lag, and help night owls shift to an earlier sleep schedule. Occasionally it’s used to correct a melatonin deficiency, or for insomnia (although for insomnia it’s unlikely to yield much benefit).
But supplements like melatonin are not subject to the same quality controls as prescription medications. A new study of melatonin sold over-the-counter shows that information on the label often does not reflect the content of the product. Here are the details:
Testing for Melatonin and Serotonin
The researchers tested the contents of 30 different melatonin supplements sold in Canada (likely similar to melatonin sold in the United States). Among them were products with 16 different brand names (the names were not published), in 5 different strengths, and in 7 different formulations, some containing herbal additives and others without. They wanted to see how closely the amount of melatonin listed on the label matched the melatonin content of the actual supplement.
They also screened for serotonin. Serotonin is a precursor of melatonin found in the herbal extracts with which commercial melatonin is often combined.
Variation in Melatonin Content
Holy cow! The actual melatonin content of the supplements varied quite a lot from the content listed on the labels. Some labels overstated the amount of melatonin contained in the product. The worst offender here was a capsule listed as containing 3 mg of melatonin that actually contained about 0.5 mg.
Other labels greatly underrepresented the amount of melatonin in the product. The worst offender here was a chewable tablet listed as containing 1.5 mg of melatonin that actually contained nearly 9 mg. (This is particularly concerning since chewable tablets are most often taken by children.)
Not only was the melatonin content of the product off by more than 10% of the listed content in about 71% of the products tested. As shocking as this may seem, the melatonin content varied widely from lot to lot of the same product. While the first lot of the chewable tablets cited above contained nearly 9 mg of melatonin, the second lot contained only 1.3 mg. That’s a variation of 465%.
Variation Could Be a Problem
Does the dose of melatonin you take matter? To some extent, yes, say the authors of a commentary on the study. Suboptimal doses might be ineffective. Taking too low a dose might lead you to believe melatonin didn’t work when a higher dose would.
Higher-than-advisable doses could lead to undesirable side effects. Too high a dose would be risky for people taking medications that interact with melatonin, or those who are pregnant or have diabetes. And the long-term effects of supplementary melatonin on prepubertal children are still unknown.
So what are we to do with this information in light of the fact that the researchers haven’t revealed the names of the products they studied? Here’s a summary of what they learned, which, if you take or are contemplating taking melatonin, is worth consideration.
- The least variable products overall were those containing the simplest mix of ingredients: the tablets or sublingual tablets with melatonin added to a filler. Apparently, added herbal extracts tend to make products more variable.
- Except for the chewable tablet cited above, capsules generally showed the greatest lot-to-lot variability in melatonin content. (However, the melatonin content of some capsules was within 10% of the content listed on the label).
- Unexpectedly, the three liquid products tested showed fairly high stability and low lot-to-lot variability.
- The melatonin content of products listed as containing 1 or 1.5 mg of melatonin was quite a bit more likely to diverge from what was claimed than were products listed as containing higher doses. Products purportedly containing 1.5 mg of melatonin were also quite a bit more variable from lot to lot.
Eight of the 30 products tested contained unlisted serotonin. While the presence of serotonin is hard to explain in supplements containing just melatonin and a filler, it might be expected in supplements containing herbal extracts. In one such product, a capsule listed as containing 3 mg of melatonin plus lavender, chamomile, and lemon balm, the serotonin content was assessed at 74 micrograms.
Serotonin raises significant health concerns if taken in excess, the Canadian authors say. It can lead to a condition called serotonin syndrome, which can be mild or fatal and “exacerbated by interactions with other medications, such as selective serotonin reuptake inhibitors and the analgesic tramadol.”
I’d like to see the content of supplementary melatonin sold in the U.S. tested and reviewed by brand and formulation. ConsumerLab? Otherwise for people using over-the-counter melatonin (or interested in trying it) it’s a kind of Wild West situation when it comes to knowing which brand to buy. Pharmacists and doctors who prescribe melatonin may be better informed. Comments?