Whey protein supplementation and muscle mass: current perspectives

Whey is one of the high-quality sources of protein with a higher proportion of indispensable amino acids compared to other sources. Its high leucine concentration makes whey an optimal protein source to maximize muscle protein synthesis (MPS) and to attenuate muscle protein breakdown at rest and following exercise. This review describes the main characteristics of the currently commercialized whey protein products and summarizes the available scientific evidence on the use of whey protein supplementation to maximize muscle mass gain in young adults without considering the impact on strength performance. Results of studies conducted on humans to date indicate that the integration of whey protein in the diet of resistance-trained individuals is effective in order to maximize muscle mass accession. Nonetheless, the observed improvements are minimized when the total daily protein intake reaches a minimum of ≥1.6 g/kg. Under resting conditions, a single serving of ∼0.24 g/kg body mass seems to be enough for stimulating a maximal postprandial response of MPS. Although this amount is effective to significantly promote an anabolic response after exercise, higher single doses of protein >0.40 g/kg after high volume workouts, involving large muscle mass, along with a minimum daily protein intake of >1.6 g/kg have been proposed as optimal to maximally stimulate MPS. Additionally, it seems that consuming whey protein as a part of a multi-ingredient admixture composed of carbohydrate, other protein sources and creatine monohydrate is more beneficial in order to maximize muscle mass gain in young resistance-trained individuals. These recommendations need to be confirmed by studies analyzing the MPS response to different workout configurations using a variety of intensities, training volumes (low, moderate or high) and the amount of the exercised muscle mass.