Branched-chain amino acids (BCAAs), including leucine, isoleucine and valine, are essential amino acids that the human body cannot synthesize on its own but must obtain from food sources. These three types of BCAAs account for about one third of total muscle amino acid content in humans, making them crucial to maintaining healthy muscles. They can be found abundantly in animal products such as meat, fish, poultry, eggs etc., or more concentratedly in dietary supplements like tablets and capsules.