ST. LOUIS – Consuming a blend of proteins from soy, whey and casein provided benefits in muscle protein synthesis after exercising, according to a study that appeared on-line Jan. 23 in The Journal of Nutrition. Researchers at the University of Texas Medical Branch conducted the study on 19 young adults.

According to the researchers, the proteins from soy, whey and casein have complementary amino acid profiles and different digestion rates (amino acid release profiles). The study’s results demonstrated prolonged delivery of amino acids to muscles and extended muscle protein synthesis when subjects consumed the protein blend as compared to when they consumed a single source (whey) of protein alone.

“Sources of high-quality protein contain all the essential amino acids and have individual characteristics thought to offer a unique advantage for muscle growth,” said Blake Rasmussen, Ph.D., interim chair, Department of Nutrition and Metabolism and the study’s principle investigator. “This is the first study to test the effects of combining soy with the dairy proteins, whey and casein, for promotion of lean body mass gain.”

In the double-blind, randomized, clinical trial, the 19 young adults were studied before and after ingesting either about 19 grams of protein from the blend or about 18 grams of whey protein. Their consumption took place about one hour after high-intensity leg resistance exercise. The soy-dairy protein blend was 25% Supro isolated soy protein from Solae/DuPont Nutrition & Health, 25% whey protein isolate and 50% caseinate. Muscle biopsies were collected at rest, 3 hours after exercise and 5 hours after exercise.