JAMA Letter Questions Vitamin D Supplement Potency

SEATLLE, Wash.Bone health experts are scrutinizing the potency of vitamin D dietary supplements, according to a new research letter in Journal of American Medical Association Internal Medicine. In the letter, "Over-the-Counter and Compounded Vitamin D: Is Potency What We Expect?" author Erin LeBlanc, MD, MPH, assistant professor of endocrinology, Oregon Health & Science University, noted potency in vitamin D supplements varies, and may not match the amount listed on a label.

Using high performance liquid chromatography, researchers analyzed pill potency using five pills each from 15 different over-the-counter (OTC) cholecalciferol dietary supplements . Scientists found OTC pills contained 52 to 135 percent of the expected dose, with two-thirds of the bottles meeting USP Convention standards spread out over five pills. About 25 percent of the bottles had all five pills meet the USP standards.

LeBlanc was also a primary researcher in the recent Women's Health Initiative cohort study analyzing health risks and benefits of calcium and vitamin D supplementation (Osteoporos Int. 2013 Feb;24(2):567-80.). In the trial, more than 36,000 postmenopausal women took 1,000 mg elemental calcium carbonate and 400 IU of vitamin D(3) or placebo for an average of seven years. Researchers found the long-term use of calcium and vitamin D reduced risk of hip fracture; supplementation versus placebo produced a hazard ratio of .65.

The study found no correlation between supplementation and coronary heart disease, cardiovascular disease (CVD), stroke or total mortalityoffsetting the recent link one JAMA article drew between supplemental calcium and CVD death in men.