Milk is made of two proteins, casein and whey. Whey protein can be separated from the casein in milk or obtained as a byproduct of cheese. Whey powder is rich in carbohydrates, and on the other hand, the protein isolated from it is the king of proteins. Whey protein powder is considered a complete protein because it contains all 9 essential amino acids. Whey powder also has a very low level of lactose.