title: Biomarker-calibrated protein intake and bone health in the Women's Health Initiative clinical trials and observational study.
abstract: BACKGROUND
  The effects of dietary protein on bone health are controversial.
  
  
  OBJECTIVE
  We examined the relation between protein intake with fracture and bone mineral density (BMD) within the Women's Health Initiative (WHI).
  
  
  METHODS
  This prospective analysis included 144,580 women aged 50-79 y at baseline in the WHI clinical trials (CTs) and observational study (OS) that recruited participants in 1993-1998 with follow-up through 2011. Self-reported clinical fractures were collected semiannually through the original end of the trials (WHI CTs) and annually (WHI OS) by questionnaires. Hip fracture was adjudicated by a central review of radiology reports. BMDs for total body, hip, and spine were measured at baseline and 3 and 6 y in 9062 women at 3 WHI clinics by using dual-energy X-ray absorptiometry. Protein intake was assessed via food-frequency questionnaire and calibrated by using biomarkers of energy and protein intakes. Associations between protein intake and fracture were estimated by using Cox proportional hazards regression, and the relation between protein intake and BMD was estimated by using linear regression.
  
  
  RESULTS
  Median biomarker-calibrated protein intake was 15% of energy intake. Per 20% increase in calibrated protein intake (percentage of energy), there was no significant association with total fracture (HR: 0.99; 95% CI: 0.97, 1.02) or hip fracture (HR: 0.91; 95% CI: 0.84, 1.00), but there was an inverse association with forearm fracture (HR: 0.93; 95% CI: 0.88, 0.98). Each 20% increase in calibrated protein intake was associated with a significantly higher BMD for total body (mean 3-y change: 0.003 g/cm²; 95% CI: 0.001, 0.005 g/cm²) and hip (mean 3-y change: 0.002 g/cm²; 95% CI: 0.001, 0.004 g/cm²).
  
  
  CONCLUSIONS
  Higher biomarker-calibrated protein intake within the range of usual intake was inversely associated with forearm fracture and was associated with better maintenance of total and hip BMDs. These data suggest higher protein intake is not detrimental to bone health in postmenopausal women.
authors.affiliation: Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, NY (JMB); the Fred Hutchinson Cancer Research Center, Seattle, WA (AZL, JCL, YH, MLN, LFT, and RLP); the Division of Endocrinology, Diabetes and Metabolism, Ohio State University, Columbus, OH (RJ); the Department of Epidemiology, University of Iowa College of Public Health, Iowa City, Iowa (LS); the Department of Preventive Medicine, University of Tennessee Health Science Center, Memphis, TN (KCJ); and the Department of Family Medicine and Epidemiology, Memorial Hospital of Rhode Island Center for Primary Care and Prevention, Pawtucket, RI (CBE).
authors.forename: Jeannette M
authors.initials: JM
authors.lastname: Beasley
authors.forename: Andrea Z
authors.initials: AZ
authors.lastname: LaCroix
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Larson
authors.forename: Ying
authors.initials: Y
authors.lastname: Huang
authors.forename: Marian L
authors.initials: ML
authors.lastname: Neuhouser
authors.forename: Lesley F
authors.initials: LF
authors.lastname: Tinker
authors.forename: Rebecca
authors.initials: R
authors.lastname: Jackson
authors.forename: Linda
authors.initials: L
authors.lastname: Snetselaar
authors.forename: Karen C
authors.initials: KC
authors.lastname: Johnson
authors.forename: Charles B
authors.initials: CB
authors.lastname: Eaton
authors.forename: Ross L
authors.initials: RL
authors.lastname: Prentice
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008875:Middle Aged; D050280:Arm Bones; D015415:Biomarkers / Q000652:urine; D001842:Bone and Bones / Q000378:metabolism; D015519:Bone Density; D015331:Cohort Studies; D015986:Confounding Factors, Epidemiologic; D004044:Dietary Proteins / Q000009:adverse effects / Q000378:metabolism / Q000627:therapeutic use; D005500:Follow-Up Studies; D006620:Hip Fractures / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control; D015994:Incidence; D009584:Nitrogen / Q000652:urine; D015663:Osteoporosis, Postmenopausal / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control; D058866:Osteoporotic Fractures / Q000453:epidemiology / Q000209:etiology / Q000517:prevention & control; D016016:Proportional Hazards Models; D014481:United States / Q000453:epidemiology; D064887:Observational Studies as Topic; D002986:Clinical Trials as Topic
chemical_list: D015415:Biomarkers; D004044:Dietary Proteins; D009584:Nitrogen