Enlarge (credit: Getty | Tim Graham)

An eye-opening analysis of common, over-the-counter sleep aids finds they contain wildly variable amounts of melatonin, with some packing up to 347 percent of the amount on the label.

The study, published Tuesday in JAMA, found that 22 of 25 melatonin gummy products analyzed—88 percent—were inaccurately labeled. That is, they contained over 10 percent more or less melatonin than what was listed on the packaging. Together, the dietary supplement products contained a range of melatonin that spanned 1.3 mg to 13.1 mg per serving. And those actual quantities represented a range of 74 percent to 347 percent of what they were supposed to contain based on their labeling.

The finding highlights a larger concern over the quality, safety, and effectiveness of dietary supplements, which are not vetted or approved by the Food and Drug Administration like over-the-counter medicines, such as ibuprofen and allergy medicines. The multi-billion dollar industry has long shrugged off substantial concerns over quality control, safety, lack of effectiveness data, and hyped health claims.