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ORIGINAL RESEARCH COMMUNICATION |
1 From the Department of Human Movement Sciences, Nutrition and Toxicology Research Institute Maastricht, Maastricht, Netherlands (RK, NC, and LJCvL); the Department of Human Biology, Nutrition and Toxicology Research Institute Maastricht, Maastricht University, Maastricht, Netherlands (APG and WHMS); the Human Nutrition Unit, Université Clermont Auvergne, Centre de Recherche en Nutrition Humaine BP 321, Clermont-Ferrand, France (SW and YB); INRA, Agrocampus Ouest, UMR1253, Rennes, France (JF); DSM Food Specialties, Research and Development, Biochemistry and Nutrition Department, Delft, Netherlands (AKK); Unité Mixte de Recherches sur la Production du Lait, INRA, Saint Gilles, France (SL); and Top Institute Food and Nutrition, Wageningen, Netherlands (LJCvL).
2 Supported by a grant from DSM Food Specialties (Delft, Netherlands). 3 Address correspondence to LJC van Loon, Department of Human Movement Sciences, Maastricht University, PO Box 616, 6200 MD Maastricht, Netherlands. E-mail: l.vanloon{at}hb.unimaas.nl.
Background: It has been suggested that a protein hydrolysate, as opposed to its intact protein, is more easily digested and absorbed from the gut, which results in greater plasma amino acid availability and a greater muscle protein synthetic response.
Objective: We aimed to compare dietary protein digestion and absorption kinetics and the subsequent muscle protein synthetic response to the ingestion of a single bolus of protein hydrolysate compared with its intact protein in vivo in humans.
Design: Ten elderly men (mean ± SEM age: 64 ± 1 y) were randomly assigned to a crossover experiment that involved 2 treatments in which the subjects consumed a 35-g bolus of specifically produced L-[1-13C]phenylalanine-labeled intact casein (CAS) or hydrolyzed casein (CASH). Blood and muscle-tissue samples were collected to assess the appearance rate of dietary protein–derived phenylalanine in the circulation and subsequent muscle protein fractional synthetic rate over a 6-h postprandial period.
Results: The mean (±SEM) exogenous phenylalanine appearance rate was 27 ± 6% higher after ingestion of CASH than after ingestion of CAS (P < 0.001). Splanchnic extraction was significantly lower in CASH compared with CAS treatment (P < 0.01). Plasma amino acid concentrations increased to a greater extent (25–50%) after the ingestion of CASH than after the ingestion of CAS (P < 0.01). Muscle protein synthesis rates averaged 0.054 ± 0.004% and 0.068 ± 0.006%/h in the CAS and CASH treatments, respectively (P = 0.10).
Conclusions: Ingestion of a protein hydrolysate, as opposed to its intact protein, accelerates protein digestion and absorption from the gut, augments postprandial amino acid availability, and tends to increase the incorporation rate of dietary amino acids into skeletal muscle protein.
This article has been cited by other articles:
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  L. J. C. van Loon, Y. Boirie, A. P. Gijsen, J. Fauquant, A. L. de Roos, A. K. Kies, S. Lemosquet, W. H. M. Saris, and R. Koopman The production of intrinsically labeled milk protein provides a functional tool for human nutrition research J Dairy Sci, October 1, 2009; 92(10): 4812 - 4822. [Abstract] [Full Text] [PDF]
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 R. Koopman, S. Walrand, M. Beelen, A. P. Gijsen, A. K. Kies, Y. Boirie, W. H. M. Saris, and L. J. C. van Loon Dietary Protein Digestion and Absorption Rates and the Subsequent Postprandial Muscle Protein Synthetic Response Do Not Differ between Young and Elderly Men J. Nutr., September 1, 2009; 139(9): 1707 - 1713. [Abstract] [Full Text] [PDF]
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