Protein is essentially a macronutrient that is found in high quality in dairy products, nuts, beans and meat, among other food items. It is made up of amino acids that are the building blocks of muscle tissues. These also keep skin, hair, bones and fingernails healthy. Different protein supplements are used for varied purposes. The most common supplements that are used for bodybuilding are Soy, Egg, Whey and Casein. Keep on reading to know more about these protein sources.