Protein Type, Protein Dose, and Age Modulate Dietary Protein Digestion and Phenylalanine Absorption Kinetics and Plasma Phenylalanine Availability in Humans

Stefan H. M. Gorissen, Jorn Trommelen, Imre W. K. Kouw, Andrew M. Holwerda, Bart Pennings, Bart B. L. Groen, Benjamin T. Wall, Tyler A. Churchward-Venne, Astrid M. H. Horstman, Rene Koopman, Nicholas A. Burd, Cas J. Fuchs, Marlou L. Dirks, Peter T. Res, Joan M. G. Senden, Jan M. J. M. Steijns, Lisette C. P. G. M. de Groot, Lex B. Verdijk, Luc J. C. van Loon*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Background: Dietary protein ingestion stimulates muscle protein synthesis by providing amino acids to the muscle. The magnitude and duration of the postprandial increase in muscle protein synthesis rates are largely determined by dietary protein digestion and amino acid absorption kinetics.

Objective: We assessed the impact of protein type, protein dose, and age on dietary protein digestion and amino acid absorption kinetics in vivo in humans.

Methods: We included data from 18 randomized controlled trials with a total of 602 participants [age: 53 +/- 23 y; BMI (kg/m(2)): 24.8 +/- 3.3] who consumed various quantities of intrinsically L-[1-C-13]-phenylalanine-labeled whey (n = 137), casein (n = 393), or milk (n = 72) protein and received intravenous infusions of L-[ring-H-2(5)]-phenylalanine, which allowed us to assess protein digestion and phenylalanine absorption kinetics and the postprandial release of dietary protein-derived phenylalanine into the circulation. The effect of aging on these processes was assessed in a subset of 82 young (aged 22 +/- 3 y) and 83 older (aged 71 +/- 5 y) individuals.

Results: A total of 50% +/- 14% of dietary protein-derived phenylalanine appeared in the circulation over a 5-h postprandial period. Casein ingestion resulted in a smaller (45% +/- 11%), whey protein ingestion in an intermediate (57% +/- 10%), and milk protein ingestion in a greater (65% +/- 13%) fraction of dietary protein-derived phenylalanine appearing in the circulation (P <0.001). The postprandial availability of dietary protein-derived phenylalanine in the circulation increased with the ingestion of greater protein doses (P <0.05). Protein digestion and phenylalanine absorption kinetics were attenuated in older when compared with young individuals, with 45% +/- 10% vs. 51% +/- 14% of dietary protein-derived phenylalanine appearing in the circulation, respectively (P = 0.001).

Conclusions: Protein type, protein dose, and age modulate dietary protein digestion and amino acid absorption kinetics and subsequent postprandial plasma amino acid availability in vivo in humans. These trials were registered at clinicaltrials.gov as NCT00557388, NCT00936039, NCT00991523, NCT01317511, NCT01473576, NCT01576848, NCT01578590, NCT01615276, NCT01680146, NCT01820975, NCT01986842, and NCT02596542, and at http://www.trialregister.nl as NTR3638, NTR3885, NTR4060, NTR4429, and NTR4492.

Original languageEnglish
Pages (from-to)2041-2050
Number of pages10
JournalJournal of Nutrition
Volume150
Issue number8
DOIs
Publication statusPublished - Aug 2020

Keywords

  • healthy aging
  • muscle protein synthesis
  • muscle mass maintenance
  • splanchnic extraction
  • sarcopenia
  • INTRINSICALLY LABELED MILK
  • ACID TRANSPORTER EXPRESSION
  • HEALTHY OLDER MEN
  • SYNTHESIS RATES
  • RESISTANCE EXERCISE
  • SYNTHETIC RESPONSE
  • WHEY-PROTEIN
  • AMINO-ACIDS
  • MICELLAR CASEIN
  • MUSCLE

Cite this