Protein supplementation has been around for many years in an effort to provide the body with the essential amino acids it needs to build new muscle. Protein is a “perfect nutrient” because it supplies all of the necessary functions of food: building tissues, providing energy, and regulating metabolism. Trying to decide which protein to use and how much is a time consuming and mind boggling process. Fortunately, there are two proteins that are used extensively, and they are both derived from milk: whey protein and casein protein. The difference is that whey is a fast-acting protein and casein is a slow-acting protein. In other words, the body digests whey a lot quicker than casein. This is not to say that whey is a better source because it all depends on your ultimate goal and how you wish to use the product.