Article Review: Whey Vs Soy Vs Casein Protein and its influence on hypertrophy
Article: Tang, J.E., Moore, D.R., Kujbida, G.W., Tarnopolsky, M.A. and Phillips, S.M., 2009. Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. Journal of applied physiology, 107(3), pp.987-992.
Design: A group of 18 men completed the test trialling 3 different proteins, Whey protein hydrolysate, soy protein isolate, and micellar casein.
Findings: No change in plasma insulin level. All caused a rise in AA (Both BCAA and EAA), with whey. With whey protein leucine was 73% higher than soy, and 200% higher than casein. Muscle protein synthesis (MPS) at rest showed whey stimulated MPS 18% higher than soy and 93% higher than casein. After exercise however whey showed a MPS level 31% higher than soy and 122% for casein.
Limitations: Small study group of only 18 men.
My Thoughts: Whey and Soy are both "fast acting" proteins, where as Casein is a "slow acting" protein. I really liked that they altered the grams of each protein to match the EAA's so it was comparable apples to apples. Th eSoy protein was supposedly matched for digestibility as most are, so that it matched the amount of absorbable protein as whey, however this study showed it didn't match for skeletal muscle protein absorption as whey was 31% higher than soy, showing that whilst is not actually utilised at the same rate as whey. This study showed that whey protein has a clear better utilisation rate than soy and casein, the large increase in casein can be due to the fact it is a slow acting protein which normally down regulates protein breakdown, rather than acting to create new protein. From this study, whey is a much more efficient way to get enough quality protein for muscle repair, soy protein is still a viable source, just be aware than when consuming, it is not efficient for muscle repair, you may need to look at increasing the dosage and spreading it out across a few hours.