Supplementation with high doses of vitamin D in postmenopausal women was not associated with improvements in bone mineral density, muscle function, muscle mass, or falls, according to the results of a trial published online August 3 in JAMA Internal Medicine.
Karen E. Hansen, MD, MS, and colleagues compared the effects of placebo, low-dose cholecalciferol (800 IU of vitamin D3 daily), and high-dose cholecalciferol (50,000 IU of vitamin D3 twice monthly) on changes in bone and muscle outcomes after one year in 230 postmenopausal women aged 75 years or younger with vitamin D insufficiency (baseline levels of 25-hydroxyvitamin D at 14 ng/mL to 27 ng/mL) and no osteoporosis.
The researchers found that calcium absorption increased by 1% in those taking a high dose of vitamin D, whereas it decreased by 2% in those taking a low dose and by 1.3% in those on placebo. They found no difference among the three groups for changes in bone mineral density (spine, average total-hip, average femoral neck, or total-body), trabecular bone score, muscle mass, sit-to-stand tests, numbers of falls, number of fallers, physical activity, or functional status.
The authors noted that their study was limited to one year, and longer exposure to high doses of vitamin D may have a greater effect on bone mineral density.