The study, “Treatment of Vitamin D Insufficiency in Postmenopausal Women,” was published today in Journal of the American Medical Association (JAMA) Internal Medicine. The study looked at 230 postmenopausal women, 75 years or younger, at UW Hospital in Madison, Wisconsin from May 2010 until mid-2014.
“We did this study because there is a worldwide debate on the impact of Vitamin D on musculoskeletal health. It’s all over the map. Some groups say you don’t need any vitamin D, while other groups say you need high dosages,” said Hansen.
“We found no data to support the need for high doses of Vitamin D in post-menopausal women with baseline serum vitamin D levels around 20 ng/mL. We found that low and high doses had no impact on the bone and muscle outcomes, compared to placebo.”
In the placebo-controlled, double-blind study, women were randomly assigned to one of three “arms”: placebo only, low-dose vitamin D or high-dose vitamin D. After one year of therapy, their calcium absorption, bone-mineral density, muscle mass and function, and number of falls were measured.
Those in the high-dose group reached and maintained a vitamin D blood level of ≥30 nanograms per milliliter for one year, which is the level currently recommended by some researchers. (Women were chosen for the study because post-menopausal women are at highest risk for osteoporosis.)
There was a small, one percent increase in calcium-absorption in the high-dose arm, but that did not translate into any benefit to bone density, muscle function, muscle mass, or falls.
“Vitamins and supplements are always hot topics in science and this study gives a more reasonable approach to Vitamin D,” said Hansen. “Our health care dollars could be better spent on other preventive measures. Our study shows that in postmenopausal women whose vitamin D levels are about 20 ng at baseline, pushing levels higher did not translate into clinical benefits. Instead, the study supports the Institute of Medicine conclusion that vitamin D repletion is a serum 25(OH)D level of ≥20 ng/mL.”
The clinical trial is number NCT00933244.
University of Wisconsin School of Medicine and Public Health