More evidence that you don’t really know what you are getting when you buy dietary supplements: A recent study in the Journal of Clinical Medicine tested 16 brands of melatonin (used for sleep and jet lag) and found that they contained anywhere from only one-fifth the dose of melatonin on the label to nearly five times more than stated on the label. In seven out of ten products, the actual dose was more than 10 percent lower or higher than stated.
Even for the same exact product, testing showed that the melatonin content of different lots sometimes varied considerably. Further analysis showed that one-quarter of the supplements also contained small amounts of serotonin, a related brain chemical that was not disclosed on the labels and could cause adverse effects.
One way to help ensure reliability of supplements is to look for the USP Verified seal, which means that a product meets the requirements of the U.S. Pharmacopeial Convention.