title: Low vitamin D status adversely affects bone health parameters in adolescents.
abstract: BACKGROUND
  The effects of subclinical vitamin D deficiency on bone mineral density (BMD) and bone turnover in adolescents, especially in boys, are unclear.
  
  
  OBJECTIVE
  We aimed to investigate the relations of different stages of vitamin D status and BMD and bone turnover in a representative sample of adolescent boys and girls.
  
  
  METHODS
  BMD was measured by dual-energy X-ray absorptiometry at the nondominant forearm and dominant heel in a random sample of 12- (n = 260) and 15-y-old (n = 239) boys and 12- (n = 266) and 15-y-old (n = 250) girls. Serum 25-hydroxyvitamin D, parathyroid hormone, osteocalcin, and type I collagen cross-linked C-telopeptide were assessed by using enzyme-linked immunoassays. Relations between vitamin D status and bone health indexes were assessed by using regression modeling.
  
  
  RESULTS
  Using multivariate regression to adjust for potential physical, lifestyle, and dietary confounding factors, we observed that 12- and 15-y-old girls with high vitamin D status (>/=74.1 nmol/L) had significantly greater forearm (but not heel) BMD (beta = 0.018; SE = 0.008; P < 0.05 for each age group) and lower serum parathyroid hormone concentrations and bone turnover markers than did those with low vitamin D status. These associations were evident in subjects sampled throughout the year and in winter only. There was no significant relation between vitamin D status and BMD in boys.
  
  
  CONCLUSIONS
  Maintaining serum 25-hydroxyvitamin D concentrations above approximately 50 nmol/L throughout the year may be a cost-effective means of improving bone health. Increased emphasis on exploring strategies for improving vitamin D status in adolescents is needed.
authors.affiliation: Department of Food and Nutritional Sciences, University College, Western Road, Cork, Ireland. k.cashman@ucc.ie
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Cashman
authors.forename: Tom R
authors.initials: TR
authors.lastname: Hill
authors.forename: Alice A
authors.initials: AA
authors.lastname: Cotter
authors.forename: Colin A
authors.initials: CA
authors.lastname: Boreham
authors.forename: Werner
authors.initials: W
authors.lastname: Dubitzky
authors.forename: Liam
authors.initials: L
authors.lastname: Murray
authors.forename: Jj
authors.initials: J
authors.lastname: Strain
authors.forename: Albert
authors.initials: A
authors.lastname: Flynn
authors.forename: Paula J
authors.initials: PJ
authors.lastname: Robson
authors.forename: Julie Mw
authors.initials: JM
authors.lastname: Wallace
authors.forename: Mairead
authors.initials: M
authors.lastname: Kiely
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D017195:Adolescent Nutritional Physiological Phenomena; D015519:Bone Density / Q000502:physiology*; D050071:Bone Density Conservation Agents / Q000008:administration & dosage / Q000097:blood*; D001842:Bone and Bones / Q000378:metabolism*; D002648:Child; D024042:Collagen Type I / Q000097:blood; D003430:Cross-Sectional Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007494:Ireland; D008297:Male; D015999:Multivariate Analysis; D015675:Osteocalcin / Q000097:blood; D010281:Parathyroid Hormone / Q000097:blood; D010455:Peptides / Q000097:blood; D012044:Regression Analysis; D012621:Seasons; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000097:blood*; D014808:Vitamin D Deficiency / Q000378:metabolism / Q000503:physiopathology*
chemical_list: D050071:Bone Density Conservation Agents; D024042:Collagen Type I; D010281:Parathyroid Hormone; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D015675:Osteocalcin; D014807:Vitamin D; C104450:25-hydroxyvitamin D