GLOSSARY

BCAA is the abbreviation for branched-chain amino acids, not a separate nutrient. This entry explains the shorthand on sport products and in training literature.

Leucine, isoleucine and valine form the three branched-chain amino acids and are all essential for humans. BCAA abbreviates that group rather than naming a fourth amino acid. Many protein foods contain them, so adequate food protein itself contributes to their intake without automatically requiring a separate branded product.

New protein synthesis requires the necessary amino acid mixture, not only activation of a cellular signal. Leucine participates in signalling but cannot replace missing essential substrates. BCAAs supply only part of that set and should not automatically be equated with sufficient food protein or a complete essential-amino-acid supplement.

Initial branched-chain amino acid processing occurs substantially in tissues such as muscle, and oxidation can change during exercise. This is not the main fuel pathway for every session and does not automatically require extra BCAAs. An amino acid used for energy also need not have come from newly broken-down muscle protein.