Melatonin levels in sleep aid gummies can be up to 350% off, according to a new study.

The study, published in JAMA on Tuesday, discovered that 22 of 25 melatonin gummy products tested (88 percent) were mislabeled. That is, they had more or less melatonin than was specified on the box. Melatonin levels in the dietary supplement items ranged from 1.3 mg to 13.1 mg per serving. And those actual quantities ranged from 74% to 347 % of what they were expected to contain based on their labelling.

The discovery underlines a broader worry about the quality, safety, and efficacy of nutritional supplements, which are not evaluated or approved by the Food and Drug Administration like over-the-counter pharmaceuticals like ibuprofen and allergy medications. The multibillion-dollar industry has long ignored serious concerns about quality control, safety, a lack of effectiveness data, and exaggerated health claims.

While the effects of a melatonin overdose are unlikely to be acutely harmful or life-threatening, the discovery is troubling because melatonin can have unpleasant side effects and is routinely used in youngsters. Children are more likely to be given gummy versions of the supplement, which is the subject of the current study.

Melatonin is a hormone that the brain produces in response to darkness, and supplement manufacturers have marketed it as a potential sleep aid and relaxant. Although some studies show that melatonin supplements help youngsters sleep better than a placebo, the research is limited, and its administration is fraught with uncertainty. The appropriate amount and timing, as well as long-term effects and if it could influence hormonal development in children and young people, are all unknowns.