When sunshine is scarce, vitamin D can be pretty hard to come by–it’s why most doctors recommend supplements. But even if you follow your doctor’s orders, you might be taking the wrong dose: some supplement manufacturers significantly under- or overestimate the potency of their pills, according to new research published in the journal JAMA Internal Medicine.
Researchers in Portland, Oregon tested 55 bottles of OTC vitamin D from a dozen different brands. The results: some pills contained just 9 percent of the amount promised on the label. Meanwhile, other brands had almost 1.5 times the designated dose, and pill potency even varied among different pills in the same bottle.
Most people expect a product’s label to precisely reflect the contents. But it’s actually fairly standard for supplement contents to fluctuate a little within a safe range—plus or minus about ten percent. However, this new study reveals that vitamin amounts vary much more than once thought. Such high variation could be a sign of sloppy manufacturing and potential danger, says study author Erin LeBlanc, M.D., an epidemiologist and board-certified endocrinologist.
Don’t freak out about potential overdose, though. “The real concern is not getting the full amount you think you’re getting—especially because you might not notice,” says LeBlanc. After all, skimping on vitamin D heightens your risk of depression, heart disease, pregnancy problems, birth defects, skin cancer, and multiple sclerosis.
If you’ve had low levels of D in the past and feel weak or confused, see your doctor pronto. And if you feel fine, but still want to get the vitamin D dose you’re paying for? Stick to supplements with a U.S. Pharmacopeial Verified Mark, which are more likely to contain what’s promised on the label, says LeBlanc. To find out whether the bottle you have contains what it claims to, check here.
More from WH:
Why You Need Vitamin D
The Best Vitamin You Can Put In Your Body
The Remedy to Weigh Less and Smile More
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