Casein is, besides whey protein, the main protein of cow's milk. Here cows' milk proteins are composed of 20% whey protein and 80% casein. Casein has a biological value of 76, and the body can therefore proteins bad use as whey proteins. For casein has a high percentage of L-glutamine.

Unlike whey protein casein is taken up slowly and spread out over several hours by the body. Therefore, casein is ideal for taking at bedtime, because that is the night a constant supply of the body with amino acids ensures. Casein anti-catabolic (tissue degrading retardant) and has a higher proportion of lactose than whey protein. Therefore, the consumption of casein with people can lead to lactose intolerance to indigestion and bloating and flatulence. Many Casein is contained in cheese and curd cheese.