Whey protein is known to be absorbed more quickly and leads to more marked increase in muscle protein synthesis in comparison with soy protein.

Volek and colleagues conducted a study to ascertain if whey supplementation promotes greater increases in muscle mass compared to soy or carbohydrate. Non-resistance-trained men and women were allocated into three groups that consumed daily isocaloric supplements containing carbohydrate, whey protein, or soy protein. The carbohydrate (carb) group comprised of 22 participants, whey protein group had (whey) 19 participants and soy protein group had (soy) 22 participants. All participants went through a supervised, whole-body periodized resistance training program of 96 workouts over a span of approximately 9 months.

Daily protein intake (including supplement) for carb, whey, and soy was 1.1, 1.4, and 1.4 g/kg body mass, respectively. Lean body mass gains were found to be significantly greater in whey, in comparison with carb and soy groups (Fig. 1). Fat mass was found to decrease slightly with no differences between groups. Fasting concentrations of leucine were significantly increased (20%) and post-exercise plasma leucine showed more than 2-fold increase in whey supplement group. Fasting leucine concentrations were positively correlated with lean body mass responses.

The study revealed that while the consumption of calories and protein was similar during resistance training, daily supplementation with whey was more effective in promoting lean body mass gains compared with soy protein or isocaloric carbohydrate control treatment conditions. It is thus evident that protein quality is a significant determinant of lean body mass responses to resistance training.

Reference

1. Volek JS, Volk BM, Gómez AL, et al.Whey protein supplementation during resistance training augments lean body mass.J Am CollNutr. 2013;32(2):122-35.