When It Comes to Bone, Vitamin D Supplementation Falls Short

Calcium supplements, which are taken by nearly half of U.S. adults for skeletal benefits, often include vitamin D. However, the role of vitamin D supplementation itself in maintaining bone quality remains unclear: Vitamin D supplements have not lowered fracture risk, and their effect on bone-mineral density (BMD) has varied. In a meta-analysis, investigators combined data from 23 randomized controlled trials (4082 adult participants; 92% women) in which BMD was a measured outcome and in which inclusion or dose of vitamin D varied. Studies differed in patients' mean baseline 25-hydroxyvitamin D level, vitamin D dose and duration, and concomitant interventions (primarily calcium supplementation).

Patients who took vitamin D supplements had significantly greater increases in BMD at the femoral neck but not at the total hip, lumbar spine, forearm, or total body. Vitamin D supplementation was associated with significantly greater increases in BMD at the total hip in studies where mean baseline 25-hydroxyvitamin D level was <20 ng/mL and at the lumbar spine in studies where vitamin D dose was less than 800 IU daily. Otherwise, outcomes were similar among trials.