Effects of dietary protein intake on skeletal muscle accretion are not well understood.
To determine plasma amino acid appearance rate and hormonal responses of active men after ingestion of whey protein.
Ten healthy, active (participating in at least 4 hours of structured exercise/week) men ingested 52 grams of whey protein isolate following an overnight fast. Blood was collected at baseline and 60, 180, 360, and 480 minutes after consumption for analysis of plasma concentrations of leucine (LEU), glutamine (GLN), insulin, testosterone, growth hormone (GH), insulin-like growth factor-1 (IGF-1), cortisol and glucagon.
LEU, GLN and insulin concentrations peaked 60 minutes after consumption with increases of 349 ± 97, 129 ± 20, and 153 ± 37 % respectively, from baseline assessment (p < 0.05). GH concentration increased (p < 0.05) from 2.9 ± 0.4 ng/ml to 8.8 ± 5.3 ng/ml three hours after whey ingestion. Plasma concentrations of testosterone, IGF-1, cortisol and glucagon did not fluctuate significantly (p > 0.05) from baseline throughout the 8-hour period.
These data suggest that the metabolic responses that could potentially favor anabolism are maximal relatively soon (1–3 hours) after consumption of a whey protein load.
Supported by a grant from NEXT Proteins International, Inc.