OBJECTIVE: To examine the evidence underpinning recommendations to increase calcium intake through dietary sources or calcium supplements to prevent fractures.
DESIGN: Systematic review of randomised controlled trials and observational studies of calcium intake with fracture as an endpoint. Results from trials were pooled with random effects meta-analyses.
DATA SOURCES: Ovid Medline, Embase, PubMed, and references from relevant systematic reviews. Initial searches undertaken in July 2013 and updated in September 2014.
ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Randomised controlled trials or cohort studies of dietary calcium, milk or dairy intake, or calcium supplements (with or without vitamin D) with fracture as an outcome and participants aged >50.
RESULTS: There were only two eligible randomised controlled trials of dietary sources of calcium (n=262), but 50 reports from 44 cohort studies of relations between dietary calcium (n=37), milk (n=14), or dairy intake (n=8) and fracture outcomes. For dietary calcium, most studies reported no association between calcium intake and fracture (14/22 for total, 17/21 for hip, 7/8 for vertebral, and 5/7 for forearm fracture). For milk (25/28) and dairy intake (11/13), most studies also reported no associations. In 26 randomised controlled trials, calcium supplements reduced the risk of total fracture (20 studies, n=58,573; relative risk 0.89, 95% confidence interval 0.81 to 0.96) and vertebral fracture (12 studies, n=48,967. 0.86, 0.74 to 1.00) but not hip (13 studies, n=56,648; 0.95, 0.76 to 1.18) or forearm fracture (eight studies, n=51,775; 0.96, 0.85 to 1.09). Funnel plot inspection and Egger's regression suggested bias toward calcium supplements in the published data. In randomised controlled trials at lowest risk of bias (four studies, n=44,505), there was no effect on risk of fracture at any site. Results were similar for trials of calcium monotherapy and co-administered calcium and vitamin D. Only one trial in frail elderly women in residential care with low dietary calcium intake and vitamin D concentrations showed significant reductions in risk of fracture.
CONCLUSIONS: Dietary calcium intake is not associated with risk of fracture, and there is no clinical trial evidence that increasing calcium intake from dietary sources prevents fractures. Evidence that calcium supplements prevent fractures is weak and inconsistent.
Recommending calcium both dietary and supplemental with or without vitamin D has been advocated for virtually everyone. This meta-analysis clearly demonstrates no benefit from increased dietary calcium. There was marginal benefit for all fractures and vertebral fractures, but no benefit for hip and forearm in calcium supplement. The studies, however, supporting this may reflect bias rather than truth and significant issues with tolerability and potential for GI upset and kidney stones (perhaps cardiac issues) make the possible marginal benefit difficult to justify on a population basis.
This study challenges the orthodox and common sense approach to calcium supplementation, implying there is no protective effect of calcium except in a small subgroup of sedentary malnourished women. I would ask for more and better studies before abandoning treatment of dietary deficiencies, but it does temper my appetite for wholesale supplementation of otherwise healthy free-living adults.
A second study showing that calcium supplements do not produce the fracture reduction that has long been purported. It is welcome evidence, even if not really new. There is evidence that large doses of plain calcium increase vascular calcifications, so these supplements are not without harm.
This is a carefully done and reported systematic review of cohort and RCTs of calcium supplementation in older adults with outcomes of bone fractures. As one would expect, cohort (but not RCTs) showed modest reductions. It's likely to influence guidelines.
Well done systematic review that highlights the lack of data to support a widespread recommendation to increase calcium intake.
A great example of how we have been conned by the supplements industry. Good lifestyle and normal diet are enough!