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 February
11, 2013, 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. The researchers were surprised by
the variation in potency among these vitamin D pills. The greatest concern is that
individuals with low levels of vitamin D in their blood and consistently taking
a supplement with little vitamin D in it, could face health consequences.
The U.S. Food and Drug Administration (FDA) 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. Dr. 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 Erin S. LeBlanc, MD, MPH, lead author and investigator with
the Kaiser Permanente Center for Health Research in Portland, Oregon.
"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, Oregon. The
compounded vitamin D was made by a compounding pharmacy in Portland. The
analysis was conducted by Eagle Analytical Services, an independent lab in
Houston.
USP Verified Dietary Supplements
Click
on the brand names below to see a list of USP Verified products and a list of
the retail stores where you can buy the products.
Note: I use Nature Made Multi For
Her 50+, a multivitamin that contains 1000 IU vitamin D3. There are also several
Nature Made vitamin D supplements: Vitamin
D—400 IU, Vitamin D3 1000 IU Softgels, Vitamin D3 2000 IU Softgels, and Vitamin
D3 5000 IU Softgels. This brand is carried at several brick-and-mortar stores.
I buy mine online at www.iherb.com. If you
use my code, KAP600, at checkout, you and I both get a discount.
