Compared to casein, whey protein is digested faster and has a higher leucine content than casein. This explains the higher post-exercise muscle protein synthesis rates observed after consumption of 100% whey products. Casein, on the other hand, provides a more moderate and prolonged rise in plasma amino acid concentrations. This means it is often selected for sports nutrition formulations where the time between meals is longer, for example, overnight. Historically, the choice between whey and casein has been a fairly black and white decision for sports nutrition formulators.
Relatively few studies have explored the differences in digestion, absorption or muscle protein synthesis between 100% whey and whey + casein blends. But those that have done so, suggest some interesting potential developments. In 2018, Traylor et al found that a whey + casein blend resulted in a rapid peak in blood amino acid concentrations (similar to whey), and was able to sustain high amino acid concentrations later. Reviewing this and other literature last year, Gorissen et al. came to a similar conclusion.
Neither of these compared the effects of the different sources on muscle protein synthesis stimulation. Two researchers (Churchward-Venne et al., and Mitchell et al.) who did test this were unable to conclude definitively that these differences also carry through to muscle protein synthesis. Certainly, more studies to measure the effect of whey + casein blends on muscle mass, strength and function are needed. Progressive research like this is an essential aspect of FrieslandCampina Ingredients’s business, and the driver behind our long-standing cooperation with research institutes, universities and industry leaders. But based on what has been deduced so far, the development of products containing both whey and casein, perhaps in tailored proportions, could be an interesting and differentiating route to explore for the increasingly competitive sports nutrition sector.