Importance: Osteoporotic fractures result in significant morbidity and mortality.
Objective: To update the evidence for benefits and harms of vitamin D, calcium, or combined supplementation for the primary prevention of fractures in community-dwelling adults to inform the US Preventive Services Task Force.
Data sources: PubMed, EMBASE, Cochrane Library, and trial registries through March 21, 2017; references; and experts. Surveillance continued through February 28, 2018.
Study selection: English-language randomized clinical trials (RCTs) or observational studies of supplementation with vitamin D, calcium, or both among adult populations; studies of populations that were institutionalized or had known vitamin D deficiency, osteoporosis, or prior fracture were excluded.
Data extraction and synthesis: Dual, independent review of titles/abstracts and full-text articles and study quality rating using predefined criteria. Random-effects meta-analysis used when at least 3 similar studies were available.
Main outcomes and measures: Incident fracture, mortality, kidney stones, cardiovascular events, and cancer.
Results: Eleven RCTs (N = 51 419) in adults 50 years and older conducted over 2 to 7 years were included. Compared with placebo, supplementation with vitamin D decreased total fracture incidence (1 RCT [n = 2686]; absolute risk difference [ARD], -2.26% [95% CI, -4.53% to 0.00%]) but had no significant association with hip fracture (3 RCTs [n = 5496]; pooled ARD, -0.01% [95% CI, -0.80% to 0.78%]). Supplementation using vitamin D with calcium had no effect on total fracture incidence (1 RCT [n = 36 282]; ARD, -0.35% [95% CI, -1.02% to 0.31%]) or hip fracture incidence (2 RCTs [n = 36 727]; ARD from the larger trial, -0.14% [95% CI, -0.34% to 0.07%]). The evidence for calcium alone was limited, with only 2 studies (n = 339 total) and very imprecise results. Supplementation with vitamin D alone or with calcium had no significant effect on all-cause mortality or incident cardiovascular disease; ARDs ranged from -1.93% to 1.79%, with CIs consistent with no significant differences. Supplementation using vitamin D with calcium was associated with an increased incidence of kidney stones (3 RCTs [n = 39 213]; pooled ARD, 0.33% [95% CI, 0.06% to 0.60%]), but supplementation with calcium alone was not associated with an increased risk (3 RCTs [n = 1259]; pooled ARD, 0.00% [95% CI, -0.87% to 0.87%]). Supplementation with vitamin D and calcium was not associated with an increase in cancer incidence (3 RCTs [n = 39 213]; pooled ARD, -1.48% [95% CI, -3.32% to 0.35%]).
Conclusions and relevance: Vitamin D supplementation alone or with calcium was not associated with reduced fracture incidence among community-dwelling adults without known vitamin D deficiency, osteoporosis, or prior fracture. Vitamin D with calcium was associated with an increase in the incidence of kidney stones.