Dr Blake Rasmussen, professor and interim chair of the Department of Nutrition & Metabolism at the University of Texas Medical Branch was the senior author of this study, titled 'Effect of protein blend versus whey protein ingestion on muscle protein synthesis following resistance exercise'. He will present the findings of the study in full at the American College of Sports Medicine annual meeting from May 29 to June 2 in San Francisco.
"This study confirms that consuming a blend of proteins (soy, whey and casein) versus whey protein alone provides a prolonged delivery of amino acids to the muscles, making it optimal for consumption following resistance exercise," said Rasmussen.
The protein in the blend used consisted of 25% isolated soy protein, 25% isolated whey protein and 50% casein. This combination of protein blends was determined in a preclinical study, presented at Experimental Biology 2011.
Soy, whey and casein proteins are all absorbed at different rates during digestion. Whey protein is referred to as a 'fast' protein because it is rapidly absorbed, whereas casein is referred to as a 'slow' protein, which requires several hours to be digested.
The ability of soy protein to deliver amino acids is 'intermediate', meaning concentrations in blood peak somewhat later than whey, but its digestion rate is much quicker than casein.
Hence, the effect of all three of these proteins combined appears to provide the extended release of amino acid delivery to the muscles.