Organic compounds that form the building blocks of proteins.Out of 20 or more, 9 are considered essential , indispensable to life and growth that the body cannot make and must be supplied by diet. They are: threonine, leucine, isoleucine, valine, lysine, methionine, phenylalanine, and tryptophan. They are found in complete protein foods such as eggs, milk, cheese, meats and fish. See complete protein.
