Protein makes up approximately 80% of the dry-weight of skeletal muscle and muscle cells need an abundant and constant supply of amino acids for renewal, repair, and synthesis of new proteins. Whey is a highly bioavailable protein source that contains an abundance of essential branched chain amino acids or BCAAs (i.e., leucine, isoleucine, and valine) vital for muscle growth—especially when consumed around the training window. The BCAA Leucine makes up only 5 to 10% of proteins and blood leucine levels are known to decline by about 30% during strength training and 11 to 33% during fat burning cardio sessions (i.e., aerobic exercise). Thus, it makes sense that leucine requirements are much higher in athletes.
A recent study published in Biology of Sport analyzed the effects of leucine-enriched whey protein supplementation on muscle anabolic signaling in healthy, resistance-trained males. They found that postworkout supplementation with leucine-enriched whey protein augmented intramuscular protein synthesis. Furthermore, they found that the addition of leucine to postworkout whey promoted a greater insulin response—which boosts anabolism and the shuttling of nutrients into fatigued muscle.
ACTION POINT: Although this study shows that you can boost the anabolic response to weight training with as little as 10 g of whey fortified with 10 g of leucine—we suggest an even more potent cocktail. Mix 20-30 g of whey protein isolate with 10-15 g of BCAA’s (2:1:1; leucine:isoleucine:valine) and drink immediately post workout. This will ensure you have at least 10 g of leucine board, but also reap the science backed benefits of whey and additional BCAAs.
Reference: Lane MT, Herda TJ, Fry AC, Cooper MA, Andre MJ, Gallagher PM. Endocrine responses and acute mTOR pathway phosphorylation to resistance exercise with leucine and whey. Biol Sport. 2017 Jun;34(2):197-203.