Casein Protein is another form of a milk protein. Since casein protein takes longer to get through the stomach, it is considered to be a slower absorbing protein than whey protein.
Both whey protein and casein protein stimulate protein synthesis. However, casein protein promotes it to a much lesser extent. However, casein protein has anticatabolic properties in that it helps decrease the breakdown of protein.
Combining both casein and whey protein can create an ideal environment for building muscle.