title: Calcium supplementation and bone mineral accretion in adolescent girls: an 18-mo randomized controlled trial with 2-y follow-up.
abstract: BACKGROUND
  A recent meta-analysis raised doubt as to whether calcium supplementation in children benefits spine and hip bone mineral density (BMD).
  
  
  OBJECTIVE
  We used state-of-the-art measures of bone (fan-beam dual-energy X-ray absorptiometry and 4 bone turnover markers) to determine whether girls with low habitual calcium intake benefited from supplementation with a soluble form of calcium (calcium citrate malate dissolved in a fruit drink).
  
  
  METHODS
  The trial was an 18-mo randomized trial of calcium supplementation (792 mg/d) with follow-up 2 y after supplement withdrawal. Subjects were 96 girls (mean age: 12 y) with low calcium intakes (mean: 636 mg/d). The main outcome measure was change in total-body, lumbar spine, and total hip bone mineral content (BMC) during supplementation and 2 y after supplement withdrawal. Changes in BMD and bone turnover markers were secondary outcome measures.
  
  
  RESULTS
  The mean additional calcium intake in the supplemented group was 555 mg/d. Compared with the control group, the supplemented group showed significantly (P < 0.05) greater gains in BMC (except at the total hip site) over the 18-mo study. BMD change was significantly (P < 0.05) greater for all skeletal sites, and concentrations of bone resorption markers and parathyroid hormone were significantly (P < 0.01) lower in the supplemented group than in the control group after 18 mo. After 42 mo, gains in BMC and BMD and differences in bone resorption were no longer evident.
  
  
  CONCLUSIONS
  Calcium supplementation enhances bone mineral accrual in teenage girls, but the effect is short-lived. The likely mechanism for the effect of the calcium is suppression of bone turnover, which is reversed upon supplement withdrawal.
authors.affiliation: Academic Unit of Bone Metabolism, School of Medicine and Biomedical Sciences, University of Sheffield, Sheffield, United Kingdom.
authors.forename: Helen L
authors.initials: HL
authors.lastname: Lambert
authors.forename: Richard
authors.initials: R
authors.lastname: Eastell
authors.forename: Kavita
authors.initials: K
authors.lastname: Karnik
authors.forename: Jean M
authors.initials: JM
authors.lastname: Russell
authors.forename: Margo E
authors.initials: ME
authors.lastname: Barker
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D017668:Age of Onset; D015415:Biomarkers / Q000097:blood; D015519:Bone Density / Q000187:drug effects*; D001846:Bone Development; D016723:Bone Remodeling / Q000187:drug effects*; D002113:Calcification, Physiologic / Q000187:drug effects; D002118:Calcium; D002136:Calcium, Dietary / Q000008:administration & dosage*; D002648:Child; D019343:Citric Acid / Q000008:administration & dosage; D019587:Dietary Supplements; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008159:Lumbar Vertebrae / Q000378:metabolism; D008293:Malates / Q000008:administration & dosage; D008572:Menarche; D009043:Motor Activity
chemical_list: D015415:Biomarkers; D002136:Calcium, Dietary; D008293:Malates; D019343:Citric Acid; C083976:calcium citrate malate; D002118:Calcium