title: Vitamin D deficiency and associated factors in adolescent girls in Beijing.
abstract: BACKGROUND
  Several locally published reports indicate a high prevalence of vitamin D deficiency among adolescents in China, but no systematic population-based survey has been conducted.
  
  
  OBJECTIVE
  The objective was to determine the prevalence of vitamin D deficiency and to study associated factors in adolescent girls in Beijing.
  
  
  METHODS
  A cross-sectional study was conducted in a random sample of 1248 Beijing girls aged 12-14 y. Nutrient intakes, ultraviolet light exposure, anthropometric characteristics, physical activity, signs and symptoms of rickets, and plasma concentrations of 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and calcium were measured and X-rays of the hand and wrist were taken.
  
  
  RESULTS
  The prevalence of clinical vitamin D and calcium deficiency (plasma 25-hydroxyvitamin D <12.5 nmol/L, plasma calcium <2.25 mmol/L, and muscle spasm at least once per week) was 9.4% in winter. The prevalence of subclinical vitamin D deficiency (25-hydroxyvitamin D <12.5 nmol/L) was 45.2% in winter and 6.7% in summer (P < 0.0005). Logistic regression analysis showed that subclinical and clinical vitamin D deficiency in winter were associated with low plasma 25-hydroxyvitamin D concentrations (<12.5 nmol/L) in summer, low calcium intake ( x +/- SD: 280 +/- 48 compared with 440 +/- 61 mg/d), and low plasma calcium concentrations (<2.25 mmol/L) in winter. The odds ratios for these associations were 3.1, 1.5, and 1.5, respectively.
  
  
  CONCLUSIONS
  Subclinical vitamin D deficiency was widespread among Beijing adolescent girls in winter. Low plasma 25-hydroxyvitamin D concentrations in summer, low calcium intake, and low plasma calcium concentrations in winter were the main risk factors for vitamin D deficiency in winter.
authors.affiliation: Department of Food Science and Technology, University of New South Wales, New South Wales, Australia. xdu@vetsci.usyd.edu.au
authors.forename: X
authors.initials: X
authors.lastname: Du
authors.forename: H
authors.initials: H
authors.lastname: Greenfield
authors.forename: D R
authors.initials: DR
authors.lastname: Fraser
authors.forename: K
authors.initials: K
authors.lastname: Ge
authors.forename: A
authors.initials: A
authors.lastname: Trube
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D002118:Calcium / Q000008:administration & dosage* / Q000097:blood; D002648:Child; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D018673:Nutrition Policy; D015995:Prevalence; D012424:Rural Population; D013472:Sunlight; D014505:Urban Population; D014807:Vitamin D / Q000008:administration & dosage* / Q000031:analogs & derivatives* / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood / Q000453:epidemiology*
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D; D002118:Calcium