|It does not necessarily have to be supplemental micellar casein. Quark, for example, is an excellent casein source you can use in "smoothies".|
As discussed in previous articles you can use this property of casein to your advantage, an advantage that makes the combination of whey and casein protein so efficient in terms of its ability to (a) boost protein synthesis (that's what the whey fraction will do) and (b) sustain the elevated protein synthesis (this is what the slowly digesting casein micelles will do).
Even when it's used on its own, though, casein protein is a very useful muscle builder, one of which we didn't know yet whether its efficacy would be impaired by the co-ingestion of the co-factors in milk, i.e. lactose, whey proteins, fat, and minerals would affect the digestion and effects of casein. More specifically, the scientists from the NUTRIM School of Nutrition and Translational Research in Metabolism in Maastricht speculated that the ingestion of casein in a milk matrix would trigger a "more rapid casein digestion and amino acid absorption, greater amino acid availability, greater whole-body protein accretion, and greater postprandial muscle protein synthesis when compared to the ingestion of isolated casein dissolved in water" (Churchward-Venne. 2015).
- 25 g intrinsically L-[1-13C]-phenylalanine and L-[1-13C]-leucine labeled casein dissolved in bovine milk serum (Cas+Serum | the serum contained ~10.3% lactose, ~0.3% protein, ~0.06% fat, and ~1.1% minerals), or
- 25 g of the same casein mixed with plain water (Cas)
The problem with casein studies is that most of them use fast digesting, "non-clumping" calcium or sodium caseinates. That's also the case for the dozens of rodent studies that claim that casein was pro-carcinogenic and what-not and it's in contrast to the studies I referred to in the introduction of this article and the study at hand. Speaking of which: I am not sure how realistic the use of milk serum and casein protein is - I mean, I'd have preferred the use of casein alone and casein + meal. This would have been a much more realistic litmus test, because the 25g casein + small quantities of lactose, fat, and other milk proteins mix used in the study at hand is not exactly close to milk or anything else you'd usually eat.The results of the experiment falsified the scientists' assumption that the addition of a milk matrix to isolated casein would result in a more rapid casein digestion and amino acid absorption, a more rapid increase in plasma amino acid availability, and subsequently greater postprandial whole-body protein accretion as well as skeletal muscle protein synthesis when compared to the ingestion of isolated casein without a milk matrix (i.e., dissolved in water).
Thus, if neither protein breakdown nor synthesis are influenced, the results of the study at hand suggest that another often advertised supplement "quality", i.e. maximal digestion speed, is practically irrelevant if you get enough protein per serving.
- Churchward-Venne, Tyler A., et al. "Ingestion of Casein in a Milk Matrix Modulates Dietary Protein Digestion and Absorption Kinetics but Does Not Modulate Postprandial Muscle Protein Synthesis in Older Men." The Journal of Nutrition (2015): jn213710.