title: Older Adults Have Delayed Amino Acid Absorption after a High Protein Mixed Breakfast Meal.
abstract: OBJECTIVE
  To measure the postprandial plasma amino acid appearance in younger and older adults following a high protein mixed meal.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  Clinical research setting.
  
  
  METHODS
  Healthy men and women aged 60-75 (n=15) years, and young controls aged 20-25 years (n=15) matched for body mass index and insulin sensitivity based on the homeostatic model assessment of insulin resistance.
  
  
  METHODS
  High protein mixed meal of complete food products.
  
  
  METHODS
  Circulating amino acid concentrations were determined hourly before and for 5 hours after meal ingestion.
  
  
  RESULTS
  There was no difference between cohorts in postprandial appearance of non-essential amino acids, or area under the curve of any individual amino acid or amino acid class. However, older adults had higher baseline concentrations of aspartic acid, glutamic acid, glycine, ornithine, threonine and tyrosine and lower baseline concentrations of hydroxyproline, isoleucine, leucine, methionine and valine compared to younger adults. Younger adults showed peak essential (EAA) and branched-chain amino acid (BCAA) concentrations at 1 hour post meal while older adults' peak EAA and BCAA concentration was at 3 hours. Similarly, peak total amino acid concentrations were at 3 hours in older adults.
  
  
  CONCLUSIONS
  Older adults digested and absorbed the protein within a mixed meal more slowly than younger adults. Delayed absorption of AA following a mixed meal of complete food products may suppress or delay protein synthesis in senescent muscle.
authors.affiliation: Cameron Mitchell, The Liggins Institute, University of Auckland, 85 Park Road, Grafton, Private Bag 92019, Auckland 1023, New Zealand. Tel: +64 (09) 9236606, Fax: (+64 9) 373 7039, Email: cameron.mitchell@auckland.ac.nz.
authors.forename: A M
authors.initials: AM
authors.lastname: Milan
authors.forename: R F
authors.initials: RF
authors.lastname: D'Souza
authors.forename: S
authors.initials: S
authors.lastname: Pundir
authors.forename: C A
authors.initials: CA
authors.lastname: Pileggi
authors.forename: E B
authors.initials: EB
authors.lastname: Thorstensen
authors.forename: M P G
authors.initials: MP
authors.lastname: Barnett
authors.forename: J F
authors.initials: JF
authors.lastname: Markworth
authors.forename: D
authors.initials: D
authors.lastname: Cameron-Smith
authors.forename: C J
authors.initials: CJ
authors.lastname: Mitchell
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging; D000597:Amino Acids, Branched-Chain / Q000097:blood / Q000378:metabolism*; D000601:Amino Acids, Essential / Q000097:blood / Q000378:metabolism*; D015992:Body Mass Index; D062408:Breakfast; D003430:Cross-Sectional Studies; D004044:Dietary Proteins / Q000097:blood / Q000378:metabolism*; D004435:Eating; D005260:Female; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D019518:Postprandial Period; D055815:Young Adult
chemical_list: D000597:Amino Acids, Branched-Chain; D000601:Amino Acids, Essential; D004044:Dietary Proteins