title: Diet in midpuberty and sedentary activity in prepuberty predict peak bone mass.
abstract: BACKGROUND
  An average daily calcium intake of 1300 mg is recommended for North American adolescents aged 9-18 y. However, questions remain about these recommendations.
  
  
  OBJECTIVE
  We assessed whether there is a stage of puberty when dietary calcium is more strongly related to peak bone mass, as indicated by young adult bone mass (YABM); whether dietary calcium intake > 1000 mg/d in adolescence is associated with higher YABM; and whether race affects any of these associations between dietary calcium and YABM. Secondarily, we evaluated relations between sedentariness and YABM.
  
  
  METHODS
  In a retrospective cohort study, we recruited 693 black and white women aged 21-24 y who had participated in the 10-y National Heart, Lung, and Blood Institute Growth and Health Study and measured YABM with the use of dual-energy X-ray absorptiometry. Dietary calcium and sedentary activity data, gathered through 3-d food records and self-reports of television-video viewing at 8 annual examinations, were averaged over 3 pubertal stages. Complete data were available from 161 black and 180 white females. Multiple regression, controlling for race, weight, and height, was applied to assess diet and activity relations with YABM.
  
  
  RESULTS
  Dietary calcium was most strongly associated with YABM in midpuberty. Calcium intake > 1000 mg/d was associated with higher YABM, but this association was not significant at all skeletal sites. Race did not affect the observed relations between calcium and YABM. Sedentary activity in prepuberty was inversely associated with YABM.
  
  
  CONCLUSIONS
  Interventions should focus on ensuring adequate calcium intake in midpuberty and on minimizing sedentariness in prepuberty.
authors.affiliation: Department of Nutritional Sciences and the School of Public Health, University of California, Berkeley, 94720-7360, USA. maywang@uclink.berkeley.edu
authors.forename: May-Choo
authors.initials: MC
authors.lastname: Wang
authors.forename: Patricia B
authors.initials: PB
authors.lastname: Crawford
authors.forename: Mark
authors.initials: M
authors.lastname: Hudes
authors.forename: Marta
authors.initials: M
authors.lastname: Van Loan
authors.forename: Kirstin
authors.initials: K
authors.lastname: Siemering
authors.forename: Laura K
authors.initials: LK
authors.lastname: Bachrach
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000293:Adolescent; D000328:Adult; D044383:Black People; D015519:Bone Density / Q000502:physiology*; D002136:Calcium, Dietary / Q000008:administration & dosage*; D002648:Child; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004032:Diet; D015930:Diet Records; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D011627:Puberty / Q000502:physiology*; D012189:Retrospective Studies; D013690:Television; D044465:White People
chemical_list: D002136:Calcium, Dietary