Whey Protein is one of two categories of protein found in dairy products (along with casein) and is a by-product of cheese and yogurt production. Once processed, whey protein is usually sold in powder form or mixed with powdered smoothies and beverages that also contain other nutrients. It is used as a supplement for malnutrition and protein deficiencies, or most often to increase athletic performance. Before being absorbed by the body, large fractions of protein are broken down by the body's digestive enzymes into amino acids. The amino acids are then combined in various combinations to create new proteins that the body will use to build muscle, enzymes, hormones, and other substances needed to build and function. Whey protein provides all the essential amino acids and is especially rich in leucine and cysteine. Leucine protein sources are believed to be the strongest determinant of muscle protein synthesis and growth, and is therefore the preferred choice for most gym goers. What is the difference between isolate and concentrate?