Is vitamin D supplementation really beneficial in postmenopause?
Results of a single-center study published in JAMA Internal Medicine suggest that achieving high calcium levels in postmenopause may not equate with clinical bone benefits. The findings, by investigators from the University of Wisconsin, run counter to expert recommendations for shooting for serum 25 (OD)D levels of 30 ng/mL or higher in postmenopausal women.
The randomized, double-blind, placebo-controlled trial was conducted from May 1, 2010 to July 31, 2013 and enrolled 230 postmenopausal women aged 75 or younger with baseline 25(OH)D levels of 14 to 27 ng/mL who did not have osteoporosis. The objective was to compare the effects of placebo and low- and high-dose calcium on 1-year changes in total fractional calcium absorption, bone mineral density (BMD), Timed Up and Go and 5 sit-to-stand tests, and muscle mass in postmenopausal women with vitamin D insufficiency.
Seventy-six of the women took daily white and twice-monthly yellow placebo, 75 took 800 IU of vitamin D3 daily and a yellow placebo twice monthly, and 79 of the women took a white placebo daily and 50,000 IU of vitamin D3 twice a month. The high-dose vitamin D regimen achieved and maintained 25(OH)D levels of ≥30 ng/mL.
To assess the impact of 1 year of therapy with placebo or low- or high-dose calcium supplementation, the investigators measured total fractional calcium absorption using 2 stable isotopes, BMD and muscle mass using dual energy x-ray absorptiometry, Timed Up and Go and 5 sit-to-stand tests, a questionnaire on functional status, and scores on physical activity scale for the elderly.
After controlling for baseline absorption, the authors found that calcium absorption increased 1% (10 mg/d) in the women who had been taking high-dose calcium and decreased 2% in those on low-dose calcium (P=.005 versus high-dose arm) and in those on placebo (P=.03 versus high-dose arm arm). There were no differences between the study arms in spine, mean total-hip, mean femoral neck, or total BMD, trabecular bone score, muscle mass, or Time Up and Go or the 5 sit-to-stand test scores. Administration of calcium also made no difference in the number of falls a woman had, the number of women who fell, or the participants’ physical activity or functional status.
The authors concluded that taking high-dose calcium increased calcium absorption but had no beneficial effects on BMD, muscle function, muscle mass, or falls. They found “no data to support experts’ recommendations to maintain serum 25(OH)D levels of 30 ng/mL or higher in postmenopausal women.”