The digestion rate of protein is an independent regulating factor of postprandial protein retention

• Published in: American journal of physiology: endocrinology and metabolism Vol. 280; no. 2; p. E340
• Main Authors: Dangin, M, Boirie, Y, Garcia-Rodenas, C, Gachon, P, Fauquant, J, Callier, P, Ballèvre, O, Beaufrère, B
• Format: Journal Article
• Language: English
• Published: United States 01-02-2001
• Subjects: Adult; Amino Acids - administration & dosage; Amino Acids - blood; Amino Acids - metabolism; Caseins - metabolism; Dietary Proteins - metabolism; Digestion - physiology; Humans; Insulin - blood; Leucine - blood; Leucine - pharmacology; Male; Milk Proteins - metabolism; Postprandial Period; Whey Proteins
• ISSN: 0193-1849
• DOI: 10.1152/ajpendo.2001.280.2.e340

To evaluate the importance of protein digestion rate on protein deposition, we characterized leucine kinetics after ingestion of "protein" meals of identical amino acid composition and nitrogen contents but of different digestion rates. Four groups of five or six young men received an L-[1-13C]leucine infusion and one of the following 30-g protein meals: a single meal of slowly digested casein (CAS), a single meal of free amino acid mimicking casein composition (AA), a single meal of rapidly digested whey proteins (WP), or repeated meals of whey proteins (RPT-WP) mimicking slow digestion rate. Comparisons were made between "fast" (AA, WP) and "slow" (CAS, RPT-WP) meals of identical amino acid composition (AA vs. CAS, and WP vs. RPT-WP). The fast meals induced a strong, rapid, and transient increase of aminoacidemia, leucine flux, and oxidation. After slow meals, these parameters increased moderately but durably. Postprandial leucine balance over 7 h was higher after the slow than after the fast meals (CAS: 38 +/- 13 vs. AA: -12 +/- 11, P < 0.01; RPT-WP: 87 +/- 25 vs. WP: 6 +/- 19 micromol/kg, P < 0.05). Protein digestion rate is an independent factor modulating postprandial protein deposition.