We know that it is crucial to optimize recovery after training to elicit maximal training adaptations. It’s been shown that a resistance exercise (RE) session has a positive impact on muscle protein synthesis, but without dietary protein intake, the net balance remains negative 1, even if carbohydrate is ingested 2. Moreover, the quality of protein sources is important to muscle anabolism 3.

Whey protein is distinguished from other protein sources due to:

  • Its rapid digestion and high content of essential amino acids (EAA), essential for stimulating skeletal muscle protein synthesis4.
  • Whey has 50% more branched-chain amino acids (BCAAs) leucine, isoleucine, and valine when compared to soy protein.
  • BCAAs are essential amino acids that promote muscle protein synthesis and prevent muscle protein breakdown 5.
  • Whey is a rich source of leucine (>10%), which by itself directly activates contractile muscle protein synthesis! 6
  • Compared to soy, whey protein following RE induces greater concentrations of leucine in the blood 7.

The acute increases in skeletal muscle protein synthesis should translate into chronic increases in lean body mass (LBM), but there is scant research on this hypothesis. A recent study published in Journal of the American College of Nutrition 8 reported LBM, body composition, and amino acid responses to 9 months of resistance training in healthy men and women randomly assigned to supplement with whey protein, soy protein, or carbohydrate. The research group hypothesized that whey protein supplementation would enhance leucine availability and gains in LBM with whole-body resistance training 8.

The research…

Participants in this study were men and women aged 18-35 years and not participating in a regular, high-intensity resistance program within 1 year before enrollment, so they were considered non-resistance trained.

The subjects were randomized into groups who consumed daily isocaloric (same calories) supplements containing carbohydrate, whey protein, or soy protein. They completed a supervised, whole-body periodized resistance training program consisting of 96 workouts (~9 months).

Body composition was measured at the start of the study and after 3, 6, and 9 months. Plasma amino acid responses to resistance exercise followed by supplement ingestion were also determined at the start of the study and at 9 months. Supplements were consumed with breakfast on non-training days and immediately after exercise on training days.

Participants in the whey and soy groups consumed ~20g/day more protein than those in carbohydrate group, which corresponded to ~1.4 and 1.1 g/kg body mass, respectively. Compliance with the supplement protocol was high at 82%.

The results…

This study was unique because: 

  • This research was the longest resistance training study to date investigating protein supplementation (i.e. 9 months)
  • First to directly compare 2 isocaloric protein sources as well as a carbohydrate control.
  • Involved a supervised resistance training protocol that included whole-body exercises.
  • Controlled protein intake throughout the intervention.

The main findings of this research are:

  • Protein quality is an important determinant of LBM responses to resistance training in the context of untrained individuals consuming protein at levels slightly greater that RDA but within the normal range of protein intake for this population.
  • Whey protein supplementation had a superior effect on LBM with effects evident after 3 months and sustained throughout 9 months of training. Lean mass gains were greater in whey (3.3kg) than carbohydrate (2.3kg) and soy (1.8kg) over the 9 month period.
  • Isocaloric supplementation with soy protein or carbohydrate was less effective in promoting gains in LBM.
  • Whey supplementation was associated with higher fasting and exercise-induced elevations in plasma leucine, which may account, in part, for greater anabolic effects in skeletal muscle.

Another important point was that there was no difference in LBM response between the carbohydrate and soy protein groups. This indicates that simply increasing protein intake from 1.1 to 1.4 g/kg body mass is not adequate to optimize muscle gains to resistance training! This highlights the importance of quality over quantity of protein in the context of being within this range of protein intakes.  

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The greater availability of leucine could be the mechanism underlying the greater adaptive response to whey protein in LBM. Leucine and more generally, BCAAs are well known to fuel for muscle along with being potent signals activating anabolic/anticatabolic response in skeletal muscle 9. This study was clear that whey was more effective than soy at elevating circulating levels of BCAAs, as well as essential amino acids (EAA) postexercise.

The authors postulate that the cumulative effect of these daily anabolic surges, although transient, may be important to optimize gains in muscle mass 8.

This research is clear that an effective strategy for increasing gains in LBM in young, healthy, untrained men and women consuming protein levels slightly above the RDA is to supplement daily with approximately 20g of whey protein during resistance training. It’s clear that protein quality is an important determinant of the adaptive response to whole-body resistance training 8.

Bottom line…

The research behind the positive benefits from whey protein isolate supplementation is numerous. AST’s VP2 Whey Isolate has been shown in clinical research to build lean muscle 10. VP2 enhances absorption kinetics that shuttle large amounts of the amino acids essential for protein synthesis directly into muscle and other tissues. The result is that there is a more potent supply of critical amino acids within muscle which promotes a more constant, uninterrupted state of protein synthesis, cell volume, and muscle anabolism!


1. Biolo G, Maggi SP, Williams BD, Tipton KD, Wolfe RR. Increased rates of muscle protein turnover and amino acid transport after resistance exercise in humans. Am J Physiol1995;268:E514-20.

2. Borsheim E, Cree MG, Tipton KD, Elliott TA, Aarsland A, Wolfe RR. Effect of carbohydrate intake on net muscle protein synthesis during recovery from resistance exercise. J Appl Physiol (1985) 2004;96:674-8.

3. Tang JE, Moore DR, Kujbida GW, Tarnopolsky MA, Phillips SM. Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. J Appl Physiol (1985) 2009;107:987-92.

4. Rasmussen BB, Tipton KD, Miller SL, Wolf SE, Wolfe RR. An oral essential amino acid-carbohydrate supplement enhances muscle protein anabolism after resistance exercise. J Appl Physiol (1985) 2000;88:386-92.

5. Karlsson HK, Nilsson PA, Nilsson J, Chibalin AV, Zierath JR, Blomstrand E. Branched-chain amino acids increase p70S6k phosphorylation in human skeletal muscle after resistance exercise. Am J Physiol Endocrinol Metab2004;287:E1-7.

6. Anthony JC, Anthony TG, Kimball SR, Jefferson LS. Signaling pathways involved in translational control of protein synthesis in skeletal muscle by leucine. J Nutr 2001;131:856S-60S.

7. Anthony TG, McDaniel BJ, Knoll P, Bunpo P, Paul GL, McNurlan MA. Feeding meals containing soy or whey protein after exercise stimulates protein synthesis and translation initiation in the skeletal muscle of male rats. J Nutr 2007;137:357-62.

8. Volek JS, Volk BM, Gomez AL, et al. Whey protein supplementation during resistance training augments lean body mass. J Am Coll Nutr 2013;32:122-35.

9. Blomstrand E, Eliasson J, Karlsson HK, Kohnke R. Branched-chain amino acids activate key enzymes in protein synthesis after physical exercise. J Nutr 2006;136:269S-73S.

10. Hayes A, Cribb PJ. Effect of whey protein isolate on strength, body and muscle hypertrophy during resistance training. Curr Opin Clin Nutr Metab Care 2008;11:40-4.

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Whey Protein vs. Soy Protein Supplementation During a Long-term Resistance Training Program

by Paul C. Henning, Ph.D. CSCS time to read: 6 min
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