Biological value (
BV) is a measure of the proportion of absorbed
protein from a food which becomes incorporated into the proteins of the organism's body. It captures how readily the digested protein can be used in
protein synthesis in the
cells of the organism. Proteins are the major source of
nitrogen in food. BV assumes protein is the only source of nitrogen and measures the proportion of this nitrogen absorbed by the body which is then excreted. The remainder must have been incorporated into the proteins of the organisms body. A ratio of nitrogen incorporated into the body over nitrogen absorbed gives a measure of protein 'usability' - the BV.