Microbial-based yeast protein is similar to whey protein and greater than collagen hydrolysate in supporting whole-body protein synthesis as determined by the indicatory amino acid oxidation method: a randomized controlled trial

Background: Yeast (Saccharomyces cerevisiae) is a model organism in agricultural and industrial fermentation with nutritional benefits, yet less is understood about its nutritional value for supporting whole-body protein synthesis in vivo, and its comparison to animal-based protein. Objective: This study aimed to determine the effect of microbial-based protein (yeast) compared to a high (whey) and low (collagen) quality animal-based protein on the ability to support whole-body protein synthesis using the indicator amino acid oxidation technique. Methods: Thirteen healthy participants (M: n=6, 24{+/-}4 yr; F: n=7, 27{+/-}7 yr) consumed eight hourly yeast (Y), whey (W), or collagen (CH) protein beverages at 0.9 g{middle dot}kg-1{middle dot}d-1 supplemented with L-[1-13C]phenylalanine in a randomized, cross-over, counterbalanced design. Breath and urine were collected to measure fraction of expired 13CO2 (F13CO2) and [1-13C]Phe oxidation (PheOx) as inverse correlates of whole-body protein synthesis. An a priori 20% noninferiority margin was used to determine equivalency between protein sources. A Visual Analog Scale (VAS) was provided to assess fullness and hunger by protein sources. Results: Protein source had no effect on F13CO2 (P=0.15) or PheRa (P=0.10). PheOx was greater in CH compared to both Y (14.94{+/-}2.16 vs. 12.93{+/-}2.80 mol{middle dot}kg BM-1{middle dot}h-1, P<0.05) and W (14.94{+/-}2.16 vs. 12.50{+/-}2.75 mol{middle dot}kg BM-1{middle dot}h-1, P<0.05) whereas there was no significant difference between Y and W (P=0.59). Change in PheOx (mean difference [90% CI]) between CH and W (2.44 mol{middle dot}kg BM-1{middle dot}h-1 [0.98, 3.90], P<0.05) and between Y and W (0.44 mol{middle dot}kg BM-1{middle dot}h-1 [-1.34, 2.21], P>0.99) confirmed respective inferiority and noninferiority to W compared to the 20% noninferiority margin (2.50 mol{middle dot}kg BM-1{middle dot}h-1), while Y was superior to CH (-2.00 mol{middle dot}kg BM-1{middle dot}h-1 [-3.01, -0.99], P<0.05). Protein source did not significantly influence satiety (P=0.32) or hunger scores (P=0.15). Conclusion: EAA-enriched whey and yeast protein similarly reduced PheOx as compared to EAA-deficient collagen hydrolysate, suggesting these proteins were similarly superior in supporting whole-body protein synthesis.