title: Dietary protein requirement of female adults >65 years determined by the indicator amino acid oxidation technique is higher than current recommendations.
abstract: BACKGROUND
  Studies on protein requirements in vulnerable groups such as older adults are few, and results are conflicting.
  
  
  OBJECTIVE
  The main objective of this study was to determine the protein requirements of free-living women >65 y by measuring the oxidation of l-[1-(13)C]phenylalanine to (13)CO2 in response to graded intakes of protein.
  
  
  METHODS
  Twelve subjects participated in the study, with protein intakes ranging from 0.2 to 2.0 g · kg(-1) · d(-1) for a total of 82 studies. The diets provided energy at 1.5 times each subject's resting energy expenditure and were isocaloric. Protein was given as an amino acid mixture on the basis of the egg protein pattern, except for phenylalanine and tyrosine, which were maintained constant across the protein intake amounts. All subjects were adapted for 2 d before the study day to a protein intake of 1.0 g · kg(-1) · d(-1). The mean protein requirement was determined by applying a mixed-effects change-point regression analysis to F(13)CO2 (label tracer oxidation in (13)CO2 breath), which identified a breakpoint in the F(13)CO2 in response to graded amounts of protein.
  
  
  RESULTS
  The mean estimated average requirement (EAR) and upper 95% CI (approximating the RDA) protein requirement of women >65 y were 0.96 and 1.29 g · kg(-1) · d(-1), respectively.
  
  
  CONCLUSIONS
  These estimates of protein requirements for older women are higher than the current EAR and RDA based on nitrogen balance data, which are 0.66 and 0.80 g · kg(-1) · d(-1), respectively. This trial was registered at clinicaltrials.gov as NCT01604980.
authors.affiliation: Research Institute, Hospital for Sick Children, Toronto, Canada.
authors.forename: Mahroukh
authors.initials: M
authors.lastname: Rafii
authors.affiliation: Research Institute, Hospital for Sick Children, Toronto, Canada.
authors.forename: Karen
authors.initials: K
authors.lastname: Chapman
authors.affiliation: Research Institute, Hospital for Sick Children, Toronto, Canada.
authors.forename: Jillian
authors.initials: J
authors.lastname: Owens
authors.affiliation: Department of Pediatrics, School of Population and Public Health, University of British Columbia, Vancouver, Canada Child & Family Research Institute, BC Children's Hospital, Vancouver, Canada.
authors.forename: Rajavel
authors.initials: R
authors.lastname: Elango
authors.affiliation: Department of Nutrition Science, Purdue University, West Lafayette, IN.
authors.forename: Wayne W
authors.initials: WW
authors.lastname: Campbell
authors.affiliation: Departments of Nutritional Sciences and Department of Agriculture, Food, and Nutritional Science, University of Alberta, Edmonton, Canada.
authors.forename: Ronald O
authors.initials: RO
authors.lastname: Ball
authors.affiliation: Research Institute, Hospital for Sick Children, Toronto, Canada Departments of Nutritional Sciences and Pediatrics, University of Toronto, Toronto, Canada; and Department of Agriculture, Food, and Nutritional Science, University of Alberta, Edmonton, Canada.
authors.forename: Paul B
authors.initials: PB
authors.lastname: Pencharz
authors.affiliation: Research Institute, Hospital for Sick Children, Toronto, Canada glenda.courtney-martin@sickkids.ca.
authors.forename: Glenda
authors.initials: G
authors.lastname: Courtney-Martin
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000596:Amino Acids / Q000008:administration & dosage; D002247:Carbon Isotopes; D004044:Dietary Proteins / Q000008:administration & dosage*; D002149:Energy Intake; D004734:Energy Metabolism; D005260:Female; D005461:Fluorine; D006801:Humans; D007553:Isotope Labeling; D009747:Nutritional Physiological Phenomena; D009751:Nutritional Requirements; D010084:Oxidation-Reduction; D010649:Phenylalanine / Q000008:administration & dosage / Q000737:chemistry; D014443:Tyrosine / Q000008:administration & dosage
chemical_list: D000596:Amino Acids; D002247:Carbon Isotopes; D004044:Dietary Proteins; D005461:Fluorine; D014443:Tyrosine; D010649:Phenylalanine
keywords: indicator amino acid oxidation; older female adults; phenylalanine oxidation; protein requirement; stable isotope