Effects of Whey Protein Hydrolysate Ingestion on Postprandial Aminoacidemia Compared with a Free Amino Acid Mixture in Young Men

To stimulate muscle protein synthesis, it is important to increase the plasma levels of essential amino acids(EAA), especially leucine, by ingestingproteins. Protein hydrolysate ingestioncan induce postprandial hyperaminoacidemia; however, it is unclear whether protein hydrolysateis associated with higher levels of aminoacidemia compared with a free amino acid mixture when both are ingestedorally. We assessed the effects of whey protein hydrolysate(WPH) ingestionon postprandialaminoacidemia, especially plasma leucinelevels, compared to ingestionof a free amino acid mixture. This study was an open-label, randomized, 4 × 4 Latin squaredesign. After 12–15 h of fasting, 11 healthy young men ingestedthe WPH (3.3, 5.0, or 7.5 g of protein) or the EAA mixture (2.5 g). Blood samples were collected before ingestionand at time points from 10 to 120 min after ingestion, and amino acids, insulin, glucose and insulin-like growth factor-1 (IGF-1) concentrations in plasma were measured. Even though the EAA mixture and 5.0 g of the WPH contained similar amounts of EAA and leucine, the WPH was associated with significantly higher plasma EAA and leucinelevels. These results suggest that the WPH can induce a higher level of aminoacidemia compared with a free amino acid mixture when both are ingestedorally.