Protein is a complex organic compound, formerly known as "prion". Amino acids are the basic units that make up proteins, and are linked by dehydration and condensation to form peptide chains. A protein is a biological macromolecule composed of one or more polypeptide chains, each of which has from twenty to hundreds of amino acid residues (-R); the various amino acid residues are arranged in a certain order. The amino acid sequence of a protein is encoded by the corresponding gene. In addition to the 20 basic amino acids encoded by the genetic code, certain amino acid residues in proteins can be post-translationally modified to undergo changes in chemical structure that activate or regulate the protein. Multiple proteins can come together, often by binding together to form stable protein complexes that fold or helix to form a certain spatial structure and thus perform a specific function. The organelle that synthesizes polypeptides is the ribosome on the stratified endoplasmic reticulum in the cytoplasm. Proteins differ in the type, number, order of amino acids and the spatial structure of the peptide chain. 

Ingested proteins are digested, hydrolyzed into amino acids, absorbed, and re-synthesized into proteins needed by the body, while new proteins are continuously metabolized and decomposed, always in a dynamic balance. Therefore, the quality and quantity of food protein and the ratio of various amino acids are related to the amount of protein synthesis in human body, especially the growth and development of adolescents, maternal health and longevity of the elderly are closely related to the amount of protein in the diet. Protein is divided into complete protein and incomplete protein. Proteins that are rich in essential amino acids and of good quality are collectively called complete proteins, such as milk, eggs, fish, meat, etc. Complete proteins are also found in soybeans from plants. Proteins that lack essential amino acids or contain very little are called incomplete proteins, such as those contained in cereals, wheat, corn, and gelatin in animal skin and bones.

At the 237th Annual Meeting of the American Chemical Society in Salt Lake City, USA, in 2009, Canadian food chemist Dr. Rotimi E. Aluko of MANITOBA University and other scientists announced a new "therapeutic" discovery: when pea proteins are hydrolyzed by the enzyme protease of Bacillus thermophilus, the pea proteins are hydrolyzed by filtration from within the membrane. This finding was verified by the consumption of a large number of rats suffering from hypertension, or hypertensive patients.