Unlike whey protein, casein protein powder is digested more slowly by the body and provides a steady stream of amino acids to the muscles, long after whey proteins have dropped off. The main benefits of casein protein powder is that it’s high in glutamine content. Out of all the protein powders, casein protein powder contains the highest amounts of the amino acid glutamine, which can benefit bodybuilders and those looking to gain weight by helping preserve muscle mass and aiding immune system function. The other significant benefit is more thorough absorption by the body. Because casein protein powder moves through the digestive tract more slowly than whey protein, it’s more likely that the body will be able to absorb and use the protein in a more efficient manner.