Evidence Level
Protein (Whey & Casein) Whey and casein proteins are well-documented in sports science research through randomized controlled trials (RCTs) and meta-analyses. Morton et al. (2018) conducted a systematic review and meta-analysis of 49 studies involving 1,863 participants, concluding that protein supplementation significantly enhances muscle strength and size during prolonged resistance training. The study highlighted that total daily protein intake is more impactful than timing or source, with a practical dose-response plateau at approximately 1.6 g/kg/day, though some evidence suggests an upper limit of ~2.2 g/kg/day.
Whey protein stands out for its ability to stimulate acute muscle protein synthesis (MPS) due to its faster digestion rate and higher leucine content. Tang et al. (2009) demonstrated that whey hydrolysate increased mixed muscle protein synthesis more effectively than casein both at rest and after resistance exercise in 18 healthy young men.
Casein offers a unique advantage for overnight protein delivery, as shown by Res et al. (2012). Consuming 40g of casein before sleep significantly increased overnight muscle protein synthesis and improved recovery in 16 males following resistance exercise (P < 0.01), highlighting its role in sustained MPS during extended periods.
Together, these studies underscore the complementary roles of whey and casein proteins in optimizing muscle growth and recovery through strategic supplementation.