Dietary protein is essential to support the turnover and reconditioning of the tissues in the body. of particular interest is skeletal muscle tissue, owing to its critical role in locomotion, significant contribution to whole-body protein turnover, myriad roles in substrate metabolism and malleability in response to diet and exercise. There is a substantial evidence base to demonstrate that protein ingestion increases muscle protein synthesis rates. The extent to which a protein can increase muscle protein synthesis is dependent upon its amino acid composition, digestibility, and ability to incite rapid and large increases in plasma amino acid concentrations. It is by these three factors that we judge the quality of a protein. There is now a wealth of evidence to demonstrate that protein quality can vary across various protein sources. However, little consideration has been given to how protein form (that is, the variation in which we consume the same protein) can modulate protein quality. Indeed, the majority of research that underpins our understanding of protein nutrition and human protein metabolism has been performed using isolated protein sources. However, the protein in our diet is ingested as wholefoods, as part of whole meals that have been cooked, processed, and prepared in a variety of ways. These factors have largely been ignored with respect to their impact on postprandial protein handling, yet all are relevant to virtually every meal that we consume. Therefore, this thesis set out to investigate how modulating protein form alters various aspects of postprandial protein metabolism.
I directly assess the role of the wholefood matrix of mycoprotein in its capacity to stimulate muscle protein synthesis. Comparing leucine matched boluses of mycoprotein (MYC; 31.5 g protein, 2.5 g leucine) and protein concentrated from mycoprotein (PCM; 28.0g protein, 2.5 g leucine), I demonstrate that the wholefood matrix of mycoprotein does not contribute to its anabolic potential, reporting equivalent (P>0.05) stimulation of muscle protein synthesis across conditions in both rested (MYC, Δ0.031±0.007%·h−1 and PCM, Δ0.020±0.008%·h−1) and exercised (MYC, Δ0.057±0.011%·h−1 and PCM, Δ0.058±0.012%·h−1) muscle. Interestingly, the equivalent stimulation of protein synthesis was observed despite plasma essential amino acid and leucine concentrations increasing more rapidly (both 60 vs 90 min; P