Like the other amino acids, Branched-Chain Amino Acids, or BCAAs, are the building blocks the body uses to make protein. Together, they represent approximately 35–40% of all essential amino acids present in your body and 14–18% of those found in your muscles (2003; Department of Nutritional Sciences, University of Toronto). Unlike the other amino acids, BCAAs are primarily broken down in muscle rather than the liver. For this reason, BCAAs are believed to provide energy during exercise, reduce muscle soreness and fatigue, assist in the process of muscle recovery, and are essential to building new muscle.
The body obtains BCAAs from proteins found in food, especially meat, dairy and legumes. Whey protein supplements also contain a high amount of BCAAs. However, BCAAs obtained from food sources such as meat and whey are in a peptide form that the body must process into a useable form.
BCAA supplements contain free-form amino acids that are readily useable by the body since they do not require digestion. While BCAA supplements come in many ratios, the most widely studied ratio is 2 parts leucine, 1 part isoleucine, and 1 part valine, or 2:1:1.