Calcium intake and bone mineral density: systematic review and meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of randomized controlled trials
PubMed 26420598 · doi:10.1136/bmj.h4183
What was done
A systematic review and random-effects meta-analysis was conducted using searches of Ovid Medline, Embase, Pubmed, and reference lists through September 2014. The authors included randomised controlled trials assessing dietary sources of calcium or calcium supplements (with or without vitamin D) in participants aged over 50 that measured bone mineral density (BMD) at the lumbar spine, total hip, femoral neck, total body, or forearm.
What was found
A total of 59 randomised controlled trials were included: 15 assessed dietary calcium sources (n=1,533) and 51 assessed calcium supplements (n=12,257). Dietary calcium increased BMD by 0.6-1.0% at the total hip and total body at 1 year, and by 0.7-1.8% at these sites, lumbar spine, and femoral neck at 2 years, with no effect at the forearm. Calcium supplements increased BMD by 0.7-1.8% across all five sites at 1, 2, and >2.5 years, with the magnitude of increase at later time points similar to that at 1 year. BMD increases were comparable between dietary sources and supplements (except forearm), monotherapy versus co-administration with vitamin D, doses of ≥1000 versus <1000 mg/day or ≤500 versus >500 mg/day, and baseline dietary calcium intake <800 versus ≥800 mg/day.
Why it matters
Increasing calcium intake via diet or supplements leads to modest, non-progressive BMD increases that plateau after 1 year. These small gains are unlikely to translate into clinically meaningful fracture prevention.
Limits
The analysis was limited to individuals over age 50. Bone mineral density is a surrogate marker rather than clinical fracture incidence, and the abstract does not report adherence rates, side effects, or long-term safety data.
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