The word protein comes from the Greek ‘‘proteios,’’ which means ‘‘of the first rank or importance.’’ Protein is indeed important for life and is involved in every biological process within the body. The average human body comprises approximately 18% protein. Proteins are essential components of muscle, skin, cell membranes, blood, hormones, antibodies, enzymes, and genetic material and almost all other body tissues and components. They serve as structural components, biocatalysts (enzymes), antibodies, lubricants, messengers (hormones), and carriers.