Don’t be overwhelmed by the endless options in the protein powder aisle. Here’s what all of the jargon means for you. Whey: A type of protein in milk. Considered a “fast” protein because it’s quickly broken down into amino acids and absorbed into your bloodstream. Casein: Another type of milk protein. Because this type is digested more slowly, it’s ideal for providing your body with smaller amounts of protein for a longer period or time—such as between meals or while you slee