Whey protein is by far the most popular type of protein supplement on the market today. You get a lot of protein per dollar spent, it tastes good, and its amino acid profile is particularly suited to muscle building. What is it, though? Well, whey is a semi-clear, liquid by-product of cheese production. After curdling and straining milk, whey is left over. It used to be thrown away as waste, but scientists discovered that it’s a complete protein. It is abundant in leucine, which is an essential amino acid that plays a key role in initiating protein synthesis.12
