title: The relative influence of calcium intake and vitamin D status on serum parathyroid hormone and bone turnover biomarkers in a double-blind, placebo-controlled parallel group, longitudinal factorial design.
abstract: BACKGROUND
  Adequate calcium and vitamin D are needed to maintain calcium balance.
  
  
  OBJECTIVE
  Our objective was to examine the influence of calcium intake and vitamin D exposure separately and their interaction on biomarkers of calcium sufficiency.
  
  
  METHODS
  Healthy men and women, age 20-80 yr, were randomly allocated to four groups: 1) double placebo, 2) calcium (1200 mg daily) plus placebo, 3) vitamin D(3) (100 microg) plus placebo, and 4) vitamin D(3) and calcium. Fasting serum and urine as well as serum and urine 2 h after a calcium load (600 mg of calcium carbonate) were obtained at baseline and 3 months.
  
  
  RESULTS
  Ninety-nine participants were randomized; 78 completed the study. Baseline demographics, protein intake and laboratory studies did not differ among the four groups. Study medication compliance was 90%. Fasting bone turnover markers declined after 3 months only in the two groups given calcium supplements and increased in the vitamin D(3) plus placebo calcium group. The calcium load resulted in a decrease in PTH and in bone turnover markers that did not differ among groups. Urinary calcium excretion increased in the combined group. Mean serum 25-hydroxyvitamin D increased from a baseline of 67 (18 sd) nmol/liter to 111 (30 sd) nmol/liter after vitamin D supplementation.
  
  
  CONCLUSIONS
  Increased habitual calcium intake lowered markers of bone turnover. Acute ingestion of a calcium load lowered PTH and bone turnover markers. Additional intake of 100 microg/d vitamin D(3) did not lower PTH or markers of bone turnover.
authors.affiliation: Bone Mineral Research Center, Winthrop University Hospital, Mineola, NY 11501, USA. jaloia@winthrop.org
authors.forename: John
authors.initials: J
authors.lastname: Aloia
authors.forename: Trajko
authors.initials: T
authors.lastname: Bojadzievski
authors.forename: Eleanor
authors.initials: E
authors.lastname: Yusupov
authors.forename: Ghulamullah
authors.initials: G
authors.lastname: Shahzad
authors.forename: Simcha
authors.initials: S
authors.lastname: Pollack
authors.forename: Mageda
authors.initials: M
authors.lastname: Mikhail
authors.forename: James
authors.initials: J
authors.lastname: Yeh
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood; D015519:Bone Density / Q000187:drug effects*; D002118:Calcium / Q000008:administration & dosage* / Q000097:blood / Q000652:urine; D002762:Cholecalciferol / Q000008:administration & dosage* / Q000097:blood / Q000652:urine; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D018579:Patient Selection
chemical_list: D015415:Biomarkers; D010281:Parathyroid Hormone; D002762:Cholecalciferol; D002118:Calcium