Your body uses protein as it's major source of material for building and repairing blood, muscles, bones, teeth, skin, hair, nails, and your internal organs. Protein comes from a Greek word meaning "of primary importance."
Protein molecules also make up certain enzymes and hormones and serve as important regulators in your body. They help maintain your blood pressure, blood sugar level, and your metabolism.
Protein is the most complex group of substances known to science. It is made up of smaller molecules called amino acids. Your body needs a total of 22 different amino acids to form all of its necessary protein. Your cells can make many of them, but 8 of them can be obtained only through the food you eat. These 8 are called the essential amino acids. They are tryptophan, lysine, methionine, phenylalanine, threonine, valine, leucine, and isoleucine.