Whole-Food Protein Sources Differentially Modulate Postprandial Plasma Dileucine Profiles in the Post-Exercise State.

Dileucine, a leucine-containing dipeptide, may enhance anabolic signaling more than leucine alone. This study examined postprandial plasma dileucine and leucine concentrations after ingesting animal- and plant- whole foods and their association with muscle protein synthesis rates (MPS). Secondary analysis was performed on plasma samples collected from two randomized controlled trials totaling 26 healthy adults (25 ± 4.3 y). Participants consumed low-fat pork (LFP), high-fat ground pork (HFP), complementary rice and beans (COMP), an iso-nitrogenous mixed nutrient beverage (ISO), or a carbohydrate control (CHO). Plasma concentrations and MPS was measured. Plasma dileucine increased significantly only after LFP ingestion (p < 0.05), with a greater 300-min iAUC compared to CHO (p = 0.038). Plasma leucine increased in all conditions except COMP and CHO with LFP demonstrating the highest concentrations (p < 0.05). A modest correlation was observed between dileucine Cmax and the change in MPS (ΔMPS; r = 0.436, p = 0.037), whereas leucine Cmax showed no significant association (r = 0.265, p = 0.102). Whole-food protein sources generally do not elevate plasma dileucine, except for LFP. While dileucine Cmax correlated with ΔMPS, the strength of this relationship suggests dileucine is likely one of several postprandial factors influencing MPS beyond free leucine.