Study highlights variability in melatonin content of dietary supplements

By Stephen Daniells contact

- Last updated on GMT

© iStock/Zerbor
© iStock/Zerbor
The melatonin content of dietary supplements may vary widely from values listed on the label, according to a new analysis from Canada that could help improve quality standards for the products.

Over 70% of 31 commercial products from 16 different brands tested did not meet within a 10% margin of the label claim, with actual content ranging from 83% less to 478% more than the label claim, according to data published in the Journal of Clinical Sleep Medicine​.

The study, performed by Lauren Erland and Prof Praveen Saxena from the Gosling Research Institute for Plant Preservation at the University of Guelph, also found serotonin in some of the products.

Erland and Saxena did not identify the products tested. In an email to NutraIngredients-USA they said that, while they have had a few inquiries and are willing to provide support upon request without disclosing any brand names, they have not initiated contact with any of the brands from the study. 

“Our lab's major focus has been on the stability and functions of melatonin and serotonin and not natural health products (NHPs) as such,” ​they explained. “The original purpose of the article was to bring awareness of the results to industry as a whole to consider unknown aspects of melatonin and serotonin biosynthesis/degradation etc. The NHP industry is striving hard to regulate the quality of their products and studies such as this may be useful to develop new strategies.”

Method development

Erland and Saxena have been developing several chemical analysis methods for detection and quantification of melatonin and serotonin in plants (for example, Erland et al., 2016, Frontiers in Plant Science​) and then surveyed natural health products as an example sample set, which would be guaranteed to contain melatonin, to help develop these methods.

Saxena and Erland told us: “What we found in this report was that melatonin values were variable, though this was not unexpected in view of the potential instability of melatonin and a lack of knowledge on interaction of melatonin with different matrices. Product quality may also be affected due to variable conditions of their transport and storage, which may span over months and years.

“In cases where medicinal ingredients are suspected to be unstable, it is not an uncommon practice for manufacturers to add more to account for potential degradation and to ensure that minimum label claim values are met,” ​he added.

“The method which we utilize for melatonin quantification has also been used for serotonin in our lab and as we ran samples we were surprised to find that this compound was present in a limited number of the samples tested. Unfortunately, we can only hypothesize as to the source of the serotonin, though it is certainly an unintended contaminant.

“This study aims to support industry efforts to improve quality and consistency in the production of natural health products through the application of basic research. We hope this report will assist industry in improving manufacturing and quality control processes,” ​said Prof Saxena and Erland.

Study details

Sales growth

Data from SPINS shows that total sales of melatonin supplements in the natural, specialty gourmet and conventional multi outlet channels grew 10.6% from 2015 to 2016 to hit $225.9 million.

Erland and Saxena purchased 31 supplements spanning 16 brands from drug stores and grocery stores in Guelph, Ontario, "some of which had specialized and very extensive natural product sections with a range of brands and dedicated staff"​, they said. The products were analyzed using ultra-performance liquid chromatography with electrochemical detection. The products included a representative sample of formulations, including liquids, capsules and chewable tablets.

The melatonin content varied from 83% less to 478% more of the label claim. For the chewable tablet that showed a 478% increase from label claim, the actual melatonin content was 9 mg (versus 1.5 mg on the label). Lot-to-lot variability within a particular product varied by as much as 465%.

Further analysis with mass spectrometry also found serotonin, a much more strictly controlled substance, in 26% of the tested supplements.

“Of these, the majority were supplements that contained other herbal supplements or extracts such as passionflower, hops, and valerian root,” ​wrote Erland and Saxena. Concentrations of serotonin ranged from 1.21 micrograms per milliliter to 74.3 micrograms per milliliter.

“The presence of serotonin in melatonin supplements is likely to open further questions on biosynthesis and degradation of these important compounds and related potential health concerns,” ​they wrote. “These results emphasize the need for further research to determine the best manufacturing procedures and mechanisms to monitor melatonin content in the products to ensure consistency and safety of the supplements.

USP

Sleeping © iStock michaeljung
The overall sleep aid category, dominated by P&G’s ZzzQuil, is growing at 27% and is expected to hit $732 million in 2018, according to Euromonitor International. Image © iStock/michaeljung

A press release from the American Academy of Sleep Medicine stated: “Because melatonin is classified as a dietary supplement, it is not subject to the same scrutiny as medications that are approved by the U.S. Food and Drug Administration. When comparing supplement labels, U.S. consumers should look for the "USP Verified" mark, which indicates that the formulation meets the requirements of the U.S. Pharmacopeial Convention.”

The Council for Responsible Nutrition issued guidelines for members who are marketing melatonin supplements targeting sleep support in 2015.

“The reason we tackled the issue is melatonin is really increasing in popularity for different sues and different populations. Our guidelines are specific to supplements containing melatonin that are marketed for sleep support,”​ Andrea Wong, PhD, CRN’s vice president of scientific and regulatory affairs, told NutraIngredients-USA at the time.

CRN recommends that, in addition to complying with all applicable labeling laws and regulations, dietary supplements containing melatonin and marketed for sleep support should be formulated and labeled to provide no more than 10 milligrams of melatonin per day when used in accordance with the directions for use.

For more information on those guidelines, please click HERE​.

Source: Journal of Clinical Sleep Medicine
2017, Volume 13, Number 2, Pages 275–281, doi: 10.5664/jcsm.6462
“Melatonin Natural Health Products and Supplements: Presence of Serotonin and Significant Variability of Melatonin Content”
Authors: L.A.E. Erland, P.K. Saxena

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