No Benefits for High-Dose Vitamin D in Postmenopausal Women
August 04, 2015Postmenopausal women who took vitamin D supplements to a level of 30 ng/mL increased calcium absorption, but that did not translate into benefits in bone density, muscle function, muscle mass, or falls in a single-center, randomized, double-blind, placebo-controlled trial. Low doses of vitamin D supplementation gave outcomes equivalent to placebo.
Karen E. Hansen, MD, from the Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, and colleagues published their findings online August 3 in JAMA Internal Medicine.
“It is possible that treatment beyond 1 year would result in better outcomes, but these data provide no support for use of higher-dose cholecalciferol replacement therapy or indeed any dose of cholecalciferol compared with placebo,” Deborah Grady, MD, MPH, from the Department of Epidemiology at the University of California, San Francisco, writes in an accompanying editorial.
The low-dose regimen consisted of 800 IU vitamin D per day, and the high-dose regimen was 50,000 IU twice monthly. Women in the high-dose group received extra doses as needed to keep their serum 25-hydroxyvitamin D levels above 30 ng/mL, the level currently recommended by some researchers. (The Institute of Medicine recommends 20 ng/mL.)
The investigators enrolled 230 postmenopausal women with 25-hydroxyvitamin D levels ranging from 14 to 27 ng/mL and counseled them to consume between 600 and 1400 mg calcium per day, an amount typical of postmenopausal American women. The study excluded women older than 75 years because age is associated with intestinal resistance to vitamin D. The researchers also excluded women with certain intestinal disorders, diabetes, or fractures or who had taken bone-active medications. The researchers stratified participants by parathyroid hormone level and calcium intake and gave the women sunscreen to use in summer months.
After 1 year, calcium absorption, the primary outcome, increased by 1% in women who received the higher dose, but decreased by 2% in those who received the low dose and 1.3% in those who received placebo.
There was no difference among the three groups in bone mineral density (adjusted P = .12), timed up-and-go and sit-to-stand tests, muscle mass, number of falls, health assessment questionnaire score, or fractures.
The investigators note that few participants were black, and the results are not generalizable to men, young adults, or women older than 75 years.
“We found no data to support experts’ recommendations to maintain serum 25(OH)D levels of 30 ng/mL or higher in postmenopausal women,” the authors conclude.
One author reported working as a local principal investigator for a Takeda clinical trial. The other authors and Dr Grady have disclosed no relevant financial relationships.
JAMA Intern Med. Published online August 3, 2015. Article abstract, Editorial extract