The research also showed a prolonged increase in amino acid – the building blocks of muscle – net balance across the leg muscle during early post-exercise recovery.
Blake Rasmussen PhD, chair of the department of nutrition and metabolism at the University of Texas and leader of the research, said: “This study sheds new light on how unique combinations of proteins, as opposed to single protein sources, are important for muscle recovery following exercise, and help extend amino acid availability, further promoting muscle growth.”
Published in the Journal of Applied Physiology, the paper follows earlier research from Solae/DuPont Nutrition & Health team that suggested soy-dairy blends offer longer muscle protein synthesis compared to unaccompanied whey, keeping synthesis rates up for three to five hours after muscle-building resistance exercise.
Muscle biopsies
The double-blind clinical trial included 16 healthy participants aged 19 to 30. The participants were given either a soy-dairy protein drink (25% isolated soy protein, 50% caseinate, 25% whey protein isolate) or a single protein source of whey isolate an hour after exercise, with muscle biopsies recorded at baseline and up to five hours later.
The researchers concluded: “While both protein sources enhanced post-exercise amino acid transporter expression, transport into muscle and myofibrillar protein synthesis, post-exercise ingestion of a protein blend results in a slightly prolonged net amino acid balance across the leg as compared to whey protein.”
The transport of the amino acid phenylalanine into muscle and messenger ribonucleic acid expression (mRNA) of some amino acid transporters increased to a similar extent in both groups. However, the mixed protein blend resulted in a “prolonged and positive net phenylalanine balance” after exercise when compared to whey protein.
“With more and more consumers recognizing the importance of protein for their overall health and well-being, the results of this study have particular relevance to a large segment of the population, from the serious sports and fitness enthusiast to the mainstream consumer,” said Greg Paul, global marketing director for DuPont.
Source: Journal of Applied Physiology
Published 3 April 2014, DOI: 10.1152/japplphysiol.01093.2013
'Soy-Dairy Protein Blend and Whey Protein Ingestion After Resistance Exercise Increases Amino Acid Transport and Transporter Expression in Human Skeletal Muscle'
Authors: P. T. Reidy , D. K. Walker , J. M. Dickinson , D. M. Gundermann , M. J. Drummond , K. L. Timmerman , M. B. Cope , R. Mukherjea , K. Jennings , E. Volpi , B. B. Rasmussen