Calcium plus vitamin D supplementation and the risk of fractures
Abstract
Randomized trials have indicated that calcium or vitamin D supplements—or both—may slow bone loss in postmenopausal women, but whether the risk of bone fracture is reduced remains uncertain. This study randomly assigned 36,282 postmenopausal women 50 to 79 years of age, who were enrolled in the Women’s Health Initiative clinical trial, to receive either 1000 mg calcium in carbonate form plus 400 IU vitamin D3 daily or placebo and followed them for an average of 7 years. Women on active treatment had levels of 25-hydroxyvitamin D 28% higher than those in placebo recipients. Bone mineral density (BMD) at the hip remained higher than in women assigned to receive placebo. The mean group difference at the ninth annual visit was 1.06%. Annualized rates of fracture per 10,000 person-years in the supplement and placebo groups were 14 and 16, respectively, for hip fracture; 44 and 44 for lower arm/wrist fractures; 14 and 15 for clinical vertebral fractures; and 164 and 170 for all fractures combined. Women assigned to supplements had a 12% lower risk of hip fracture than placebo recipients, but this was not a statistically significant effect. There were no significant group differences in rates of major diseases, including cardiovascular disease and cancer. The hazard ratio for kidney stones in women receiving supplements was 1.17 (95% confidence interval, 1.02–1.34). This finding was not related to a high baseline calcium intake. Gastrointestinal symptoms occurred in approximately…
How strong is the evidence?
Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 36,282 participants or records.
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