What Is Casein?
Casein, similar to whey, is a milk-derived protein. It contains all the essential amino acids but is digested more slowly, which is why it is often referred to as a “slow” protein. Many people choose to take a casein supplement before going to bed to ensure a steady release of protein throughout the night. This strategy is thought to help minimize protein breakdown during the fasting phase of sleep[1].
Casein is the primary protein found in milk and dairy products, making up about 80% of the total protein content in cow’s milk[2]. It is a phosphoprotein, which means it has a high affinity for calcium and phosphate ions, forming a complex known as casein micelles[3]. These micelles are responsible for the white, opaque appearance of milk and play a crucial role in the dairy industry, particularly in cheese making. During the cheese-making process, the casein proteins coagulate, trapping fat and other components to form the curd, which is then processed into cheese.
Nutritionally, casein is highly valued for its ability to provide a sustained release of amino acids into the bloodstream[4]. This slow digestion rate makes it particularly beneficial for muscle repair and growth, as it ensures a steady supply of nutrients over several hours. Athletes and bodybuilders often incorporate casein into their diets, especially before periods of fasting, such as sleep, to optimize muscle protein synthesis and recovery.
Casein also has functional benefits beyond its nutritional properties. It is used as an additive in a variety of food products to improve texture, stability, and shelf life. Its unique gelling properties make it ideal for use in products like yogurt, ice cream, and baked goods.