There are several kinds of protein supplements available: milk and egg protein, soy, beef, and even vegetable protein; but the absolutely best source of protein is ion-exchange whey protein. This protein has superior biological value (which means it may yield more usable grams of protein than other protein supplements), plus it is very low in lactose (the substance in milk that causes a lot of stomach upset and gas in individuals).
There are two main ingredients in milk protein, they are casein and whey. Whey is produced mostly from the production of cheese. Milk is treated to cause a shift in pH and the casein coagulates and separates, and raw whey is left un-curded on top of the casein. It’s then collected and undergoes various processing steps. These processing steps are what determines the quality of the whey protein end product.
During the processing, fat and lactose are filtered out to make a lower fat, lower carbohydrate, and higher concentrated protein powder. The protein content can range from 35% to 95% whey protein. Obviously, the higher the protein concentration, the more processing (filtering) is needed which adds to the cost. Generally, when the protein level reaches >90% concentration, it’s considered WPI (whey protein isolate).