Q: Does vitamin D without calcium reduce fracture risk? Evidence-based answer: No. Supplemental vitamin D without calcium -- in doses averaging as much as 800 IU per day -- doesn't reduce the risk of hip, vertebral, or nonvertebral fractures in postmenopausal women and older men (strength of recommendation [SOR]: A, large, high-quality meta-analysis of randomized or quasirandomized placebo-controlled trials). The vitamin D analogs alfacalcidol and calcitriol also don't reduce hip or nonvertebral fractures (SOR: A, multiple randomized, controlled trials [RCTs]), although alfacalcidol (but not calcitriol) does reduce vertebral fractures by 43% (SOR: B, one RCT and one quasi-randomized trial with potential for bias) Vitamin D supplementation, with or without calcium, doesn't affect mortality. It does double the risk of mild hypercalcemia (about 2.7 mmol/L increase), raise the risk of renal calculi or mild renal insufficiency by 16%, and slightly increase (4%) gastrointestinal adverse effects (SOR: A, meta-analysis of RCTs or quasi-randomized trials)
