title: Protein intake and muscle strength in older persons: does inflammation matter?
abstract: OBJECTIVE
  To examine whether protein intake is associated with change in muscle strength in older persons. Because systemic inflammation has been associated with protein catabolism, the study also evaluated whether a synergistic effect exists between protein intake and inflammatory markers on change in muscle strength.
  
  
  METHODS
  Longitudinal.
  
  
  METHODS
  The Invecchiare in Chianti Study.
  
  
  METHODS
  Five hundred and ninety-eight older adults.
  
  
  METHODS
  Knee extension strength was measured at baseline (1998-2000) and during 3-year follow-up (2001-2003) using a handheld dynamometer. Protein intake was assessed using a detailed food frequency questionnaire. The inflammatory markers examined were C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α).
  
  
  RESULTS
  The main effect of protein intake on change in muscle strength was not significant. However, a significant interaction was found between protein intake and CRP (P = .003), IL-6 (P = .049), and TNF-α (P = .02), indicating that lower protein intake was associated with greater decline in muscle strength in persons with high levels of inflammatory markers.
  
  
  CONCLUSIONS
  Lower protein intake was associated with decline in muscle strength in persons with high levels of inflammatory markers. These results may help to understand the factors contributing to decline in muscle strength with aging and to identify the target population of older persons who may benefit from nutritional interventions aimed at preventing or reducing age-associated muscle impairments and its detrimental consequences.
authors.affiliation: Channing Laboratory, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA. benedetta.bartali@channing.harvard.edu
authors.forename: Benedetta
authors.initials: B
authors.lastname: Bartali
authors.forename: Edward A
authors.initials: EA
authors.lastname: Frongillo
authors.forename: Martha H
authors.initials: MH
authors.lastname: Stipanuk
authors.forename: Stefania
authors.initials: S
authors.lastname: Bandinelli
authors.forename: Simonetta
authors.initials: S
authors.lastname: Salvini
authors.forename: Domenico
authors.initials: D
authors.lastname: Palli
authors.forename: Jose A
authors.initials: JA
authors.lastname: Morais
authors.forename: Stefano
authors.initials: S
authors.lastname: Volpato
authors.forename: Jack M
authors.initials: JM
authors.lastname: Guralnik
authors.forename: Luigi
authors.initials: L
authors.lastname: Ferrucci
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002097:C-Reactive Protein / Q000378:metabolism; D003710:Demography; D004044:Dietary Proteins / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D007249:Inflammation / Q000378:metabolism*; D015850:Interleukin-6 / Q000378:metabolism; D007558:Italy; D007719:Knee Joint / Q000502:physiology*; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D012307:Risk Factors; D011795:Surveys and Questionnaires; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D004044:Dietary Proteins; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D002097:C-Reactive Protein