Vitamin D supplements have become as ubiquitous as umbrellas during the Portland winter, but a new study shows people might need to think twice before downing Vitamin D pills to combat ailments ranging from cancer to the winter blues.
Those pills dont have in them the amount of D the bottle advertises, says Dr. Erin LeBlanc, a researcher at the Kaiser Permanente Center for Health Research in North Portland. LeBlanc published a paper this week in the Journal of the American Medical Association Internal Medicine which reveals that the potency of Vitamin D in supplements she had tested ranged from 9 percent to 146 percent of the advertised dose. Some pills had much less D than advertised, and some more. A total of 55 supplements from 12 different manufacturers were tested all purchased at Portland-area stores.
Even within one bottle of Vitamin D pills LeBlanc found huge variations in the amount of D present. Within one bottle, one pill had about half the advertised potency and another pill had 124 percent of advertised potency.
The takeaway from LeBlancs study might be to look for supplements with a USP seal of approval. That stands for U.S. Pharmacopeial Convention, a nonprofit organization that tests manufacturers products for quality, potency and purity. Few supplements have the certification since participating with USP is voluntary. LeBlanc tested one Vitamin D bottle that was USP certified and found its pills were about what they were supposed to be.
LeBlanc says she decided to have the pills tested because she was conducting a clinical trial involving the effect of Vitamin D in menopausal women. She needed to be certain the supplements had the advertised dosage if her findings were going to be valid. When she found her initial batch of pills were way off, she sent more in for testing and ended up with a different study, now published.
To complete her Vitamin D/menopause study LeBlanc says shell rely on USP certified bottles.
Vitamin D deficiency has been connected with a variety of ills and is commonly prescribed, especially in Oregon, where the angle of the sun is so low from November through February that even sunbathing Oregonians would not be able to absorb enough sunlight for their bodies to produce significant Vitamin D. Researchers have not reached consensus on an optimum amount of daily Vitamin D, or to which ailments it is connected, though some studies claim that well over half of U.S. residents are not getting enough D.