title: Association between caffeine intake and bone mass among young women: potential effect modification by depot medroxyprogesterone acetate use.
abstract: This study assessed associations between habitual caffeine intake and bone mass among young women. Analyses of the entire study population revealed no significant associations, while analyses restricted to women using depot medroxyprogesterone acetate (DMPA) showed modest inverse associations between caffeine intake and bone mineral content (BMC).
  
  
  BACKGROUND
  Some previous investigations among postmenopausal women suggest an inverse relationship between caffeine intake and bone mass, yet studies of this association among young women are few.
  
  
  METHODS
  The association between habitual caffeine intake and bone mass was evaluated prospectively in a population-based cohort of 625 females, aged 14 to 40 years, adjusting for relevant biological and lifestyle factors. Caffeinated beverage intake was self-reported, and bone mineral content (BMC) and bone mineral density (BMD) were measured at baseline and every 6 months throughout a 24-month follow-up period using dual-energy x-ray absorptiometry.
  
  
  RESULTS
  Cross-sectional analyses revealed no significant differences in mean BMC or BMD at baseline. Mean percentage and absolute changes in BMC and BMD were not associated with caffeine use. Repeated measures analyses similarly showed no significant association between caffeine intake at baseline and mean BMC or BMD measured during follow-up. However, among women using depot medroxyprogesterone acetate (DMPA), modest inverse associations between caffeine and BMC (but not BMD) were detected.
  
  
  CONCLUSIONS
  Our data suggest that heavy habitual consumption of caffeinated beverages does not adversely impact bone mass among young women in general. Greater caffeine intake may be associated with lower BMC among DMPA users.
authors.affiliation: Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle, WA 98195, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Wetmore
authors.forename: L
authors.initials: L
authors.lastname: Ichikawa
authors.forename: A Z
authors.initials: AZ
authors.lastname: LaCroix
authors.forename: S M
authors.initials: SM
authors.lastname: Ott
authors.forename: D
authors.initials: D
authors.lastname: Scholes
mesh_terms: D015502:Absorptiometry, Photon / Q000295:instrumentation; D000293:Adolescent; D000328:Adult; D015519:Bone Density / Q000187:drug effects* / Q000502:physiology; D002110:Caffeine / Q000009:adverse effects / Q000378:metabolism*; D000697:Central Nervous System Stimulants / Q000009:adverse effects / Q000378:metabolism*; D003271:Contraceptive Agents, Female / Q000009:adverse effects / Q000378:metabolism*; D005260:Female; D050723:Fractures, Bone / Q000139:chemically induced / Q000503:physiopathology; D006801:Humans; D008137:Longitudinal Studies; D017258:Medroxyprogesterone Acetate / Q000009:adverse effects / Q000378:metabolism*; D015663:Osteoporosis, Postmenopausal / Q000503:physiopathology / Q000517:prevention & control*; D016896:Treatment Outcome
chemical_list: D000697:Central Nervous System Stimulants; D003271:Contraceptive Agents, Female; D002110:Caffeine; D017258:Medroxyprogesterone Acetate