Native whey induces higher and faster leucinemia than other whey protein supplements and milk: A randomized controlled trial

Background: Resistance exercise and protein intake are both strong stimuli for muscle protein synthesis. The potential for a protein to acutely increase muscle protein synthesis seems partly dependent on absorption kinetics and the amino acid composition. The aim of this double-blinded randomized cross-over study was to compare time dependent changes in blood amino acid concentrations after ingesting 20 g of five distinct high quality dairy protein supplements (native whey, whey protein concentrate 80, hydrolysed whey, microparticulated whey, and milk proteins). Furthermore, we investigated whether differences in time dependent changes in blood amino acid concentrations affected acute blood glucose and urea responses, and recovery of muscle function after a bout of strength training. Methods: Ten young healthy, recreationally active men ingested different milk protein supplements after a whole-body strength training session on five occasions in a randomized manner. Blood concentrations of amino acids, glucose and urea was measured before and 0, 30, 45, 60, 90, 120 min, and 22 and 30 h post-exercise. Maximal voluntary isometric knee extension and counter movement jump were assessed before, immediately after, 6, 22 and 30 h after exercise. Results: Intake of native whey induced a faster and higher leucinemia than the other protein supplements (p < 0.001). All whey protein supplements showed faster time dependent changes in blood amino acid concentrations for total essential and branched chain amino acids compared to milk. There were no major differences between trials in blood concentrations of glucose or urea, or recovery of muscle function after exercise. Conclusion: Native whey induced the strongest leucinemia and appears to have a greater potential for stimulating muscle protein synthesis than other whey supplements and milk. There were no meaningful differences in blood glucose, urea or recovery of muscle function after the supplements. Future studies should investigate whether the increased leucinemia with native whey translates into greater muscle protein synthesis and muscle mass accretion over time. (NCT02882386, August 16, 2016). © 2017 The Author(s).