Proteins are the building blocks of every cell in your body. Some proteins help you maintain muscle tissue, while others transport molecules or carry out chemical reactions. All proteins are made of chains of amino acids linked together. There are 20 different amino acid building blocks in proteins, and the particular sequence of amino acids in a protein determines its shape, or function. The instructions to make a protein are encoded in genes. The amino acid ‘letters’ are linked together in millions of ways to form polypeptide chains, which can twist and fold into specific 3-D structures that give proteins their shapes.
Protein foods provide the body with essential nutrients and fuel. Protein is used to build and repair tissues, regulate bodily functions, and produce hormones. Protein also provides energy by converting to ketone bodies in the liver, which are then used as fuel when needed.
Proteins are classified as complete or incomplete proteins based on how many essential amino acids they contain. Animal products (meat, fish, poultry, milk) and some plant foods (beans, soy, quinoa) are considered to be complete proteins because they contain all of the essential amino acids. Most other plant foods, however, are considered incomplete proteins because they do not provide all of the essential amino acids. Including a variety of protein sources in the diet is important to ensure that the body gets all of the amino acids it needs. peptides