title: Calcium intake and risk of fracture: systematic review.
abstract: OBJECTIVE
  To examine the evidence underpinning recommendations to increase calcium intake through dietary sources or calcium supplements to prevent fractures.
  
  
  METHODS
  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.
  
  
  METHODS
  Ovid Medline, Embase, PubMed, and references from relevant systematic reviews. Initial searches undertaken in July 2013 and updated in September 2014.
  
  
  METHODS
  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.
authors.affiliation: Department of Medicine, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand m.bolland@auckland.ac.nz.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Bolland
authors.affiliation: Department of Public Health, University of Otago, PO Box 7343, Wellington 6242, New Zealand.
authors.forename: William
authors.initials: W
authors.lastname: Leung
authors.affiliation: Department of Medicine, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Vicky
authors.initials: V
authors.lastname: Tai
authors.affiliation: Department of Radiology, Starship Hospital, Private Bag 92024, Auckland 1142, New Zealand.
authors.forename: Sonja
authors.initials: S
authors.lastname: Bastin
authors.affiliation: Department of Medicine, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Greg D
authors.initials: GD
authors.lastname: Gamble
authors.affiliation: Department of Medicine, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Andrew
authors.initials: A
authors.lastname: Grey
authors.affiliation: Department of Medicine, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand.
authors.forename: Ian R
authors.initials: IR
authors.lastname: Reid
mesh_terms: D000368:Aged; D015519:Bone Density / Q000187:drug effects*; D002136:Calcium, Dietary / Q000008:administration & dosage / Q000378:metabolism; D019587:Dietary Supplements; D050723:Fractures, Bone / Q000178:diet therapy / Q000517:prevention & control*; D016330:Frail Elderly; D006801:Humans; D008875:Middle Aged; D016032:Randomized Controlled Trials as Topic
chemical_list: D002136:Calcium, Dietary