title: Combined ingestion of protein and carbohydrate improves protein balance during ultra-endurance exercise.
abstract: The aims of this study were to compare different tracer methods to assess whole body protein turnover during 6 h of prolonged endurance exercise when carbohydrate was ingested throughout the exercise period and to investigate whether addition of protein can improve protein balance. Eight endurance-trained athletes were studied on two different occasions at rest (4 h), during 6 h of exercise at 50% of maximal O2 uptake (in sequential order: 2.5 h of cycling, 1 h of running, and 2.5 h of cycling), and during subsequent recovery (4 h). Subjects ingested carbohydrate (CHO trial; 0.7 g CHO.kg(-1.)h(-1)) or carbohydrate/protein beverages (CHO + PRO trial; 0.7 g CHO.kg(-1).h(-1) and 0.25 g PRO.kg(-1).h(-1)) at 30-min intervals during the entire study. Whole body protein metabolism was determined by infusion of L-[1-13C]leucine, L-[2H5]phenylalanine, and [15N2]urea tracers with sampling of blood and expired breath. Leucine oxidation increased from rest to exercise [27 +/- 2.5 vs. 74 +/- 8.8 (CHO) and 85 +/- 9.5 vs. 200 +/- 16.3 mg protein.kg(-1).h(-1) (CHO + PRO), P < 0.05], whereas phenylalanine oxidation and urea production did not increase with exercise. Whole body protein balance during exercise with carbohydrate ingestion was negative (-74 +/- 8.8, -17 +/- 1.1, and -72 +/- 5.7 mg protein.kg(-1).h(-1)) when L-[1-13C]leucine, L-[2H5]phenylalanine, and [15N2]urea, respectively, were used as tracers. Addition of protein to the carbohydrate drinks resulted in a positive or less-negative protein balance (-32 +/- 16.3, 165 +/- 4.6, and 151 +/- 13.4 mg protein.kg(-1).h(-1)) when L-[1-13C]leucine, L-[2H5]phenylalanine, and [15N2]urea, respectively, were used as tracers. We conclude that, even during 6 h of exhaustive exercise in trained athletes using carbohydrate supplements, net protein oxidation does not increase compared with the resting state and/or postexercise recovery. Combined ingestion of protein and carbohydrate improves net protein balance at rest as well as during exercise and postexercise recovery.
authors.affiliation: Department of Human Biology, Maastricht University, PO Box 616, 6200 MD, The Netherlands. R.Koopman@HB.unimaas.nl
authors.forename: René
authors.initials: R
authors.lastname: Koopman
authors.forename: Daphne L E
authors.initials: DL
authors.lastname: Pannemans
authors.forename: Asker E
authors.initials: AE
authors.lastname: Jeukendrup
authors.forename: Annemie P
authors.initials: AP
authors.lastname: Gijsen
authors.forename: Joan M G
authors.initials: JM
authors.lastname: Senden
authors.forename: David
authors.initials: D
authors.lastname: Halliday
authors.forename: Wim H M
authors.initials: WH
authors.lastname: Saris
authors.forename: Luc J C
authors.initials: LJ
authors.lastname: van Loon
authors.forename: Anton J M
authors.initials: AJ
authors.lastname: Wagenmakers
mesh_terms: D000328:Adult; D000465:Algorithms; D000596:Amino Acids / Q000378:metabolism; D001628:Beverages; D004032:Diet; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D004044:Dietary Proteins / Q000494:pharmacology*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects; D010649:Phenylalanine / Q000378:metabolism; D010807:Physical Endurance / Q000502:physiology*; D011506:Proteins / Q000378:metabolism*; D014508:Urea / Q000378:metabolism
chemical_list: D000596:Amino Acids; D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D011506:Proteins; D010649:Phenylalanine; D014508:Urea; D007930:Leucine