Hydrolyzed casein is absorbed faster than intact casein

Many athletes take amino acid supplements before or after training with weights to increase their strength and muscle mass. The amino acids contained in proteins act as building blocks for protein synthesis and muscle growth. In addition, key amino acids such as leucine activate chemical pathways that promote protein synthesis. Casein is the main protein component of milk and cheese. Hydrolyzed casein contains protein hydrolysates, which are small packets of amino acids that are formed when milk protein is broken down by acid or enzymes with water.
A French study found that hydrolyzed casein was absorbed faster than intact casein. The body absorbs hydrolyzed casein better than intact casein, resulting in higher blood levels of specific amino acids (e.g. leucine and phenylalanine) and a greater potential for protein synthesis. The study showed that hydrolyzed casein supplements increased blood levels of amino acids and insulin (a highly anabolic hormone) faster and more than intact casein, with intact casein being the longer acting protein.
(American Journal of Clinical Nutrition, 90:1011-1022, 2009)