There are several sources of protein powder, including whey, casein, soy, egg, and hemp. Whey protein is a by-product of cheese production and is the most popular type of protein powder. It is rich in branched-chain amino acids (BCAAs) and has a high biological value (BV). Casein protein is derived from milk and is slowly absorbed by the body, making it ideal for nighttime use. Soy protein is derived from soybeans and is a complete protein, meaning that it contains all nine essential amino acids. Egg protein comes from eggs and is also a complete protein. Hemp protein is derived from hemp seeds and is rich in omega-3 fatty acids.