title: Comparison of the effects of two different types of calcium supplementation on markers of bone metabolism in a postmenopausal osteopenic population with low calcium intake: a double-blind placebo-controlled trial.
abstract: OBJECTIVE
  To investigate calcium supplements in postmenopausal women. Calcium supplements in postmenopausal women with a low calcium intake have been shown to prevent osteoporotic vertebral fracture, but calcium is variably absorbed and often poorly tolerated, which may limit effectiveness.
  
  
  METHODS
  The study compared the efficacy and tolerability of 500 mg/day of calcium in the form of ossein-hydroxyapatite (OHC) versus 500 mg/day of tricalcium phosphate (TCP) and placebo in the prevention of postmenopausal bone loss. This was a prospective randomized study enrolling 153 postmenopausal osteopenic women. Serum and urine markers of bone turnover were collected at 3 and 6 months. Bone density measurement was performed at baseline and 6 months in all participants, and at 12 months in women taking OHC.
  
  
  RESULTS
  At 3 and 6 months, both TCP and OHC decreased serum markers of bone formation significantly, compared with placebo. At 6 months, TCP and OHC decreased osteocalcin by 9.9% and 12.3%, respectively; the aminoterminal propeptide of type I procollagen (PINP) was decreased by 5.3% and 6.3%, respectively; bone-specific alkaline phosphatase was decreased by 4.3% and 6.7%, respectively, compared with baseline. The effects on bone resorption markers or on bone mineral density did not reach statistical significance, although OHC increased bone density by 0.8% at the spine at 12 months. Both forms of calcium were well tolerated and did not differ from placebo in terms of side-effects.
  
  
  CONCLUSIONS
  While both OHC and TCP were well tolerated and significantly reduced bone turnover markers, the effect of ossein-hydroxyapatite seems slightly superior to that of tricalcium phosphate.
authors.affiliation: Centre for Metabolic Bone Disease, University of Hull, Hull Infirmary, UK.
authors.forename: P
authors.initials: P
authors.lastname: Albertazzi
authors.forename: S A
authors.initials: SA
authors.lastname: Steel
authors.forename: E M
authors.initials: EM
authors.lastname: Howarth
authors.forename: D W
authors.initials: DW
authors.lastname: Purdie
mesh_terms: D000368:Aged; D000469:Alkaline Phosphatase / Q000032:analysis; D015415:Biomarkers / Q000032:analysis; D015519:Bone Density / Q000502:physiology; D016723:Bone Remodeling / Q000187:drug effects* / Q000502:physiology; D002130:Calcium Phosphates / Q000627:therapeutic use*; D024042:Collagen Type I / Q000032:analysis; D004311:Double-Blind Method; D017886:Durapatite / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D015675:Osteocalcin / Q000032:analysis; D015663:Osteoporosis, Postmenopausal / Q000517:prevention & control*; D010446:Peptide Fragments / Q000032:analysis; D011446:Prospective Studies; D012016:Reference Values
chemical_list: D015415:Biomarkers; D002130:Calcium Phosphates; D024042:Collagen Type I; D010446:Peptide Fragments; D015675:Osteocalcin; D017886:Durapatite; D000469:Alkaline Phosphatase; C018392:tricalcium phosphate