A study by the Kaiser Permanente Center for Health Research in Portland, Oregon found that some vitamin D supplements do not contain the amount stated on the label.
The study tested 55 bottles of vitamin D3 (the type most often recommended by doctors) from 12 different brands. 5 pills from each bottle were tested for their potency. The researchers found a great variation in some of the samples tested.
Some samples contained as little as 9 percent of the amount of vitamin D3 listed on the label, while others contained up to 146 percent more vitamin D than indicated.
The variation wasn’t just found from bottle to bottle. Some of the samples tested had variations in the individual pills from the same bottle.
According to the results of the study, a good way for consumers to ensure that their vitamin D3 supplements contain the labeled amount is to look for the USP verification mark on the label. The U.S. Pharmacopeial Convention (USP) runs a quality verification program for supplements.
The researchers found that the bottle of vitamin D3 from a USP verified manufacturer was somewhat more accurate than the other bottles tested. The issue is that the USP program is voluntary and expensive for supplement manufacturers, and few manufacturers participate in the program. Many of the common drugstore brands do not have the USP verification mark on the label.
“There are not many manufacturers that have the USP mark, but it may be worth the extra effort to look for it,” said Dr. Erin LeBlanc, one of the researchers with Kaiser’s vitamin D study.
Vitamin brands that come with the USP verification include Kirkland (found at Costco), Equaline (found at Albertson’s), and Nature Made, which can be found at many drugstores and grocery stores.
Safeway’s Calcium Plus Vitamin D has the USP verification as well. Their regular vitamin D supplement does not have the verification, however.
The study said that the U.S. Food and Drug Administration is considering the possibility of regulating some supplements, but for now the supplement industry is unregulated.
The new study is published Feb. 11 in the journal JAMA Internal Medicine.
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