title: Protein type and caloric density of protein supplements modulate postprandial amino acid profile through changes in gastrointestinal behaviour: A randomized trial.
abstract: OBJECTIVE
  The requirement of leucine and essential amino acids (EAA) to stimulate muscle protein synthesis increases with age. To target muscle anabolism it is suggested that higher postprandial blood levels of leucine and EAA are needed in older people. The aim was to evaluate the impact of oral nutritional supplements with distinct protein source and energy density, resembling mixed meals, on serum amino acid profiles and on gastrointestinal behaviour.
  
  
  METHODS
  Four iso-nitrogenous protein (21 g) supplements were studied containing leucine-enriched whey protein with 150/320 kcal (W150/W320) or casein protein with 150/320 kcal (C150/C320); all products contained carbohydrates (10 or 32 g) and fat (3 or 12 g). Postprandial serum AA profiles were evaluated in twelve healthy, older subjects who participated in a randomized, controlled, single blind, cross-over study. Gastrointestinal behaviour was studied in vitro by looking at gastric coagulation and cumulative intestinal protein digestion over time.
  
  
  RESULTS
  The peak serum leucine concentration was twofold higher for W150 vs. C150 (521 ± 15 vs. 260 ± 15 μmol/L, p < 0.001), higher for W320 vs. C320 (406 ± 15 vs. 228 ± 15 μmol/L, p < 0.001), and higher for low-caloric vs. high-caloric products (p < 0.001 for pooled analyses; p < 0.001 for interaction protein source*caloric density). Similar effects were observed for the peak concentrations of EAA and total AA (TAA). In vitro gastric coagulation was observed only for the casein protein supplements. Intestinal digestion for 90 min resulted in higher levels of free TAA, EAA, and leucine for W150 vs. C150, for W150 vs. W320, and for C150 vs. C320 (p < 0.0125).
  
  
  CONCLUSIONS
  A low caloric leucine-enriched whey protein nutritional supplement provides a higher rise in serum levels of TAA, EAA and leucine compared to casein protein or high caloric products in healthy, elderly subjects. These differences appear to be mediated in part by the gastrointestinal behaviour of these products.
  
  
  BACKGROUND
  ClinicalTrials.gov: NCT02013466.
authors: Nutricia Research, Utrecht, The Netherlands; Center for Translational Research in Aging & Longevity, Dept of Health and Kinesiology, Texas A&M University, College Station, TX, USA. Electronic address: yvette.luiking@nutricia.com.
authors: Yvette C
authors: YC
authors: Luiking
authors: Nutricia Research, Utrecht, The Netherlands.
authors: Evan
authors: E
authors: Abrahamse
authors: Nutricia Research, Utrecht, The Netherlands.
authors: Thomas
authors: T
authors: Ludwig
authors: INRA, UMR 1019, UNH, CRNH Auvergne, F-63000 Clermont-Ferrand, France; Clermont University, University of Auvergne, Unité de Nutrition Humaine, BP 10448, F-63000 Clermont-Ferrand, France; CHU Clermont-Ferrand, Clinical Nutrition Department, Clermont-Ferrand F-63003, France.
authors: Yves
authors: Y
authors: Boirie
authors: Nutricia Research, Utrecht, The Netherlands.
authors: Sjors
authors: S
authors: Verlaan
mesh_terms: D000368:Aged; D000601:Amino Acids, Essential / Q000008:administration & dosage* / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D001835:Body Weight; D002097:C-Reactive Protein / Q000378:metabolism; D002364:Caseins / Q000008:administration & dosage; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage; D019587:Dietary Supplements; D002149:Energy Intake; D015444:Exercise; D005260:Female; D041981:Gastrointestinal Tract / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000097:blood; D007930:Leucine / Q000008:administration & dosage* / Q000097:blood; D008297:Male; D062407:Meals; D019518:Postprandial Period / Q000187:drug effects*; D012709:Serum Albumin / Q000378:metabolism; D016037:Single-Blind Method; D000067816:Whey Proteins / Q000008:administration & dosage* / Q000032:analysis
chemical_list: D000601:Amino Acids, Essential; D001786:Blood Glucose; D002364:Caseins; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D007328:Insulin; D012709:Serum Albumin; D000067816:Whey Proteins; D002097:C-Reactive Protein; D007930:Leucine
keywords: Bioavailability; Casein; Coagulation; Digestion; Leucine; Whey