A protein blend is simply a protein powder made from a variety of different single protein sources, such as whey, casein, and egg white protein. The idea of a 3-protein blend comes after sports nutritionists have long debated which protein source is best based on different amino acid profiles, different protein content, different biological values, and more. Consuming a mixture of proteins from three different sources (such as protein isolate, egg white protein and high-proline milk protein), means you can get the nutritional benefits of all of these proteins in one protein source.