title: Association of total protein intake with bone mineral density and bone loss in men and women from the Framingham Offspring Study.
abstract: OBJECTIVE
  To examine (i) the association of percentage of total energy intake from protein (protein intake %) with bone mineral density (BMD, g/cm2) and bone loss at the femoral neck, trochanter and lumbar spine (L2-L4) and (ii) Ca as an effect modifier.
  
  
  METHODS
  The Framingham Offspring Study.
  
  
  METHODS
  Men (n 1280) and women (n 1639) completed an FFQ in 1992-1995 or 1995-1998 and underwent baseline BMD measurement by dual-energy X-ray absorptiometry in 1996-2000. Men (n 495) and women (n 680) had follow-up BMD measured in 2002-2005.
  
  
  METHODS
  Cohort study using multivariable regression to examine the association of protein intake % with each BMD, adjusting for covariates. Statistical interaction between protein intake % and Ca (total, dietary, supplemental) intake was examined.
  
  
  RESULTS
  The mean age at baseline was 61 (sd 9) years. In the cross-sectional analyses, protein intake % was positively associated with all BMD sites (P range: 0·02-0·04) in women but not in men. Significant interactions were observed with total Ca intake (<800 mg/d v. ≥800 mg/d) in women at all bone sites (P range: 0·002-0·02). Upon stratification, protein intake % was positively associated with all BMD sites (P range: 0·04-0·10) in women with low Ca intakes but not in those with high Ca intakes. In the longitudinal analyses, in men, higher protein intake % was associated with more bone loss at the trochanter (P = 0·01) while no associations were seen in women, regardless of Ca intake.
  
  
  CONCLUSIONS
  This suggests that greater protein intake benefits women especially those with lower Ca intakes. However, protein effects are not significant for short-term changes in bone density. Contrastingly, in men, higher protein intakes lead to greater bone loss at the trochanter. Longer follow-up is required to examine the impact of protein on bone loss.
authors.affiliation: 1Institute for Aging Research,Hebrew SeniorLife,1200 Centre Street,Boston,MA 02131,USA.
authors.forename: Shivani
authors.initials: S
authors.lastname: Sahni
authors.affiliation: 1Institute for Aging Research,Hebrew SeniorLife,1200 Centre Street,Boston,MA 02131,USA.
authors.forename: Kerry E
authors.initials: KE
authors.lastname: Broe
authors.affiliation: 4Clinical Laboratory and Nutritional Sciences,University of Massachusetts,Lowell,MA,USA.
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Tucker
authors.affiliation: 1Institute for Aging Research,Hebrew SeniorLife,1200 Centre Street,Boston,MA 02131,USA.
authors.forename: Robert R
authors.initials: RR
authors.lastname: McLean
authors.affiliation: 1Institute for Aging Research,Hebrew SeniorLife,1200 Centre Street,Boston,MA 02131,USA.
authors.forename: Douglas P
authors.initials: DP
authors.lastname: Kiel
authors.affiliation: 5Boston University School of Public Health and the Framingham Heart Study,Boston,MA,USA.
authors.forename: L Adrienne
authors.initials: LA
authors.lastname: Cupples
authors.affiliation: 1Institute for Aging Research,Hebrew SeniorLife,1200 Centre Street,Boston,MA 02131,USA.
authors.forename: Marian T
authors.initials: MT
authors.lastname: Hannan
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D015519:Bone Density; D002136:Calcium, Dietary / Q000008:administration & dosage; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004044:Dietary Proteins / Q000008:administration & dosage*; D019587:Dietary Supplements; D002149:Energy Intake; D005260:Female; D005272:Femur Neck / Q000502:physiology; D005500:Follow-Up Studies; D006801:Humans; D016014:Linear Models; D008159:Lumbar Vertebrae / Q000502:physiology; D008297:Male; D008404:Massachusetts; D008875:Middle Aged; D015999:Multivariate Analysis; D015596:Nutrition Assessment; D010024:Osteoporosis / Q000503:physiopathology*; D011795:Surveys and Questionnaires; D014807:Vitamin D / Q000008:administration & dosage
chemical_list: D002136:Calcium, Dietary; D004044:Dietary Proteins; D014807:Vitamin D