Soy-Dairy Protein Extends Amino Acid Delivery to Muscles

ST. LOUIS, Mo.—Using a protein blend of soy, casein and whey post-workout prolongs the delivery of select amino acids to the muscle for an hour longer than using whey alone, according to a new study published in the Journal of Applied Physiology. It also shows a prolonged increase in amino acid net balance across the leg muscle during early post-exercise recovery, suggesting prolonged muscle building.   

The double-blind, randomized clinical trial included 16 healthy subjects, ages 19 to 30, to assess if consumption of a blend of proteins with different digestion rates would prolong amino acid availability and lead to increases in muscle protein synthesis after exercise. The protein beverages provided to study subjects consisted of a soy-dairy blend (25 percent isolated DuPont™ Danisco® SUPRO® soy protein, 50 percent caseinate, 25 percent whey protein isolate) or a single protein source (whey protein isolate). Muscle biopsies were taken at baseline and up to 5 hours after resistance exercise. The protein sources were ingested 1 hour after exercise in both groups.

Results concluded that consuming a soy-dairy blend leads to a steady rise in amino acids and an increase in select amino acid delivery for about an hour longer than the use of whey protein alone. The blend also sustained a greater positive net amino acid balance than whey, suggesting there is less muscle protein breakdown during the time period shortly after consumption of a blended protein product.

“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," said Blake B. Rasmussen, Ph.D., chair, department of Nutrition & Metabolism at the University of Texas Medical Branch and lead researcher of the study.

It's no surprise protein's popularity has been growing among consumers. The NPD Group study showed 24.9% of consumers look for protein on the Nutrition Facts label and 78% of consumers said protein contributes to a healthy diet. Half of those consumers say they want more protein in their diet.

“Because of the increased demand for high-quality protein, this study provides critical insight for the food industry as a whole, and the sports nutrition market in particular," said Greg Paul, Ph.D., global marketing director, DuPont Nutrition & Health. “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."

This is only part of a growing body of research that points to the value of dairy ingredients in sports nutrition. And dairy proteins aren't just for muscle—athletes interested in maintaining or losing weight can also benefit from high-quality dairy proteins. (Check out the "Dairy Ingredients in Sports Nutrition" Digital Issue from Food Product Design for more on this.) Coupled with soy protein ingredients—which have no cholesterol and are low in saturated fat—the possibilities are endless. For more on soy protein, check out Food Product Design's FoodTech Toolbox—the Infographic: Soy Protein Ingredients.