Use of Calcium or Calcium in Combination With Vitamin D Supplementation to Prevent Fractures and Bone Loss in People Aged 50 Years and Older: A Meta-analysis

Osteoporotic bone fractures are becoming an increasing burden worldwide—socially and economically—as the population ages. Supplemental calcium, alone or combined with vitamin D, has been proposed as a relatively inexpensive way of preventing osteoporotic bone loss, but whether it lowers the risk of fracture remains uncertain. Meta-analyses have, up to now, yielded inconsistent results. The present meta-analysis is based on 29 randomized trials totalling 63,897 adults aged 50 years and older. Seventeen trials numbering 52,625 persons reported fracture as an outcome, while 23 trials comprising 41,419 individuals reported bone mineral density (BMD) as an outcome. All trials compared calcium, alone or combined with vitamin D supplementation, with a placebo. In trials reporting fracture as an outcome, supplementation was associated with a 12% reduction in fractures of all types (risk ratio, 0.88; 95% confidence interval, 0.83–0.95; P = 0.0004). In trials reporting BMD as an outcome, treatment correlated with a reduced rate of bone loss averaging 0.54% (0.35%–0.73%; P < 0.0001) at the hip and 1.19% (0.76%–1.61%) at the spine. The reduction in fracture risk was significantly greater (by 24%) in trials with high compliance rates. A more substantial treatment effect was noted with calcium doses of 1200 or more than with lower doses (0.80 versus 0.94; P = 0.006), and with vitamin D doses of at least 800 IU (0.84 versus 0.87; P = 0.03). Neither gender nor a history of fracture influenced observed treatment effects. Adding vitamin D to calcium also did not alter treatment effects. Subjects with relatively low serum vitamin D levels had a greater risk reduction, but the difference was not significant. Lesser risk reductions were noted in persons 50–70 years of age than in those older than 70. These findings demonstrate that supplemental calcium, alone or combined with vitamin D, can prevent osteoporotic bone fractures. Analysis of the estimated number needed to treat shows that 63 patients will have to be treated over 3.5 years to prevent a single fracture. At least 1200 mg of calcium and 800 IU of vitamin D are recommended for combined supplementation.