PORTLAND, Ore., February 11, 2013 – Vitamin D supplement potency varies widely, and the amount of vitamin D in over-the counter and compounded supplements does not necessarily match the amount listed on the label, according to a research letter published in the journal JAMA Internal Medicine.
The analysis showed that the amount of vitamin D in these supplements ranged from 9 percent to 146 percent of the amount listed on the label. Not only was there variation among different brands and manufacturers, but also among different pills from the same bottle.
"We were surprised by the variation in potency among these vitamin D pills," says Erin S. LeBlanc, M.D., MPH, lead author and investigator with the Kaiser Permanente Center for Health Research in Portland, Ore. "The biggest worry is for someone who has low levels of vitamin D in their blood. If they are consistently taking a supplement with little vitamin D in it, they could face health risks."
According to a recent editorial in the New England Journal of Medicine, more than 100 million Americans spend a combined $28 billion on vitamins, herbs, and supplements each year. The U.S. Food and Drug Administration is considering new safety guidelines for some supplements but, for the most part, the industry remains unregulated.
Some manufacturers participate in a voluntary quality verification program operated by the U.S. Pharmacopeial Convention (USP)—an independent, nonprofit organization that sets public standards for the quality of dietary supplements. In order to receive the USP verification mark, manufacturers' facilities undergo annual good manufacturing practice audits, and their products are tested for quality, potency, and purity. LeBlanc and her colleagues included one supplement from a USP Verified manufacturer in their sample. They found the amount of vitamin D in pills from that bottle was generally more accurate than the other bottles tested.
"The USP verification mark may give consumers some reassurance that the amount of vitamin D in those pills is close to the amount listed on the label," said Dr. LeBlanc. "There are not many manufacturers that have the USP mark, but it may be worth the extra effort to look for it."
The researchers tested 55 bottles of over-the-counter vitamin D from 12 different manufacturers. The over-the-counter vitamin D pills used in the analysis were purchased at five different stores in Portland, Ore. The compounded vitamin D was made by a compounding pharmacy in Portland. The analysis was conducted by an independent lab in Houston.
Authors include Erin S. LeBlanc, M.D., MPH; Nancy Perrin, Ph.D.; and Teresa Hillier, M.D., MS, from the Kaiser Permanente Center for Health Research in Portland, Ore.; and Jeffery D. Johnson Jr., Ph.D., and Annie Ballatore, MS, from Eagle Analytical Services in Houston.
About the Kaiser Permanente Center for Health Research
The Kaiser Permanente Center for Health Research, founded in 1964, is a nonprofit research institution dedicated to advancing knowledge to improve health. It has research sites in Portland, Ore., Honolulu, and Atlanta. http://www.kpchr.org
About Kaiser Permanente
Kaiser Permanente is committed to helping shape the future of health care. We are recognized as one of America's leading health care providers and nonprofit health plans. Founded in 1945, our mission is to provide high-quality, affordable health care services and to improve the health of our members and the communities we serve. We currently serve more than 9 million members in nine states and the District of Columbia. Care for members and patients is focused on their total health and guided by their personal physicians, specialists and team of caregivers. Our expert and caring medical teams are empowered and supported by industry-leading technology advances and tools for health promotion, disease prevention, state-of-the-art care delivery and world-class chronic disease management. Kaiser Permanente is dedicated to care innovations, clinical research, health education and the support of community health. For more information, go to: kp.org/newscenter.
JAMA Internal Medicine