Comparison of the Amino Acid and Peptide Composition and Postprandial Response of Beef, Chicken, and Whey Protein Nutritional Preparations

Abstract

Background: Increasing dietary protein intake synergistically improves the effect of exercise to stimulate muscle protein synthesis. The purpose of this study was to evaluate the plasma amino acid response of two novel protein nutritional preparations, beef protein isolate (BeefISOTM) and hydrolyzed chicken protein isolate (MyoCHXTM). Methods: The postprandial plasma amino acid response over 3 hours was monitored in young adults (n=6) following consumption of 23 grams of WPC, BeefISOTM, or MyoCHXTM. Amino acid compositional analysis and molecular weight distributions of each protein were performed by HPLC. Statistical analyses were performed using one-way or two-way ANOVA where appropriate and corrected for multiple comparisons to account for the cross-over design. Results: Compositional evaluations revealed similar levels of essential and branched-chain amino acids for WPC and MyoCHXTM. While the results of this study predictably demonstrated plasma amino acids levels increased following consumption of the different proteins, the kinetics of the postprandial response was unique to each protein source. WPC and MyoCHXTM were rapidly absorbed with maximum plasma amino acid concentrations observed at 30 and 15 min, respectively. The slightly faster absorption of MyoCHXTM was associated with the increased peptide content of MyoCHXTM (greater than 76% of protein is <2kDa). BeefISOTM exhibited sustained release characteristics as evidenced by increased post prandial amino acid concentrations after 3 hours. Conclusions: The protein preparations studied each had different amino acid profiles and absorption kinetics. WPC and MyoCHXTM contained a higher essential amino acid content and were rapidly absorbed with plasma amino acid concentrations peaking within 30 minutes following consumption. BeefISOTM contained a higher proportion of conditionally essential amino acids that steadily increased in plasma over 3 hours, indicating a sustained release profile for BeefISOTM. Each of these three protein preparations have been shown to facilitate similar improvements in body composition following a resistance-exercise training program. The paradoxical finding that proteins with varying composition, molecular weight, and digestibility can lead to similar effects on body composition suggests the need to evaluate proteins based on total nutritional potential rather than as a delivery vehicle for single amino acids.Key Words: Protein digestibility; amino acids; body composition; beef protein; chicken protein