What is Branched-chain amino acids (BCAA)
Branched-chain amino acids (BCAA) play an important role in building and repairing muscles. They get their name from their chemical structure, which also affects the way the body uses them. The three BCAAs are leucine, valine, and isoleucine. They comprise three of the nine essential amino acids, considered necessary because the body cannot make them but must get them from food.

Most amino acids are metabolized or broken down in the liver. BCAAs are mostly metabolized in muscle tissue. That makes BCAA supplements attractive to athletes and bodybuilders, but research doesn't offer strong evidence for using BCAAs to increase muscle mass. BCAA supplements may be no better for muscle growth and recovery than BCAAs from dietary sources.

Muscle Building

Several studies suggest that BCAA supplements may increase muscle mass and strength during training. The studies were short-term and did not show that supplementing with BCAAs is superior to getting them from dietary sources.

Muscle Recovery

Some studies suggest that BCAAs may ease soreness and help recover following exercise. The effect may not be significant enough to warrant the use of supplements.
 

Those who take certain drugs may have a condition called tardive dyskinesia that causes uncontrolled movements. Some antipsychotic drugs and some anti-nausea drugs can cause this condition. Some evidence indicates that supplements of BCAAs can reduce symptoms.