The Problem with BCAA Supplements

BCAAs (leucine, isoleucine, and valine) constitute about 35% of the EAAs in muscle protein. Leucine seems to play a unique role as a regulator of muscle protein synthesis by activating molecular factors involved in the initiation of protein synthesis. For those reason, BCAA supplements are currently very popular.

However, BCAAs alone do not stimulate muscle protein synthesis, and, in fact the few studies measuring the response to BCAAs have shown either no change or a decreased rate of muscle protein synthesis. The response to BCAA ingestion, and leucine in particular, provides a good example of the circumstance in which an "activating" amino acids needs other amino acids present.

There is no doubt from molecular studies that leucine can "turn on" the muscle protein synthetic machinery by activating factors in the initiation phase of this process. However, the activation of these initiation factors does not always result in the making of muscle protein, because all of the amino acids are required to actually synthesize muscle in living beings. Leucine can be thought of as the "key to the car" that can start it up but the fuel is still required in the tank to proceed further.

Bottom Line: It takes all 20 amino acids to make one intact protein... not just 3....

Dr Robert Wolfe: Build It Stronger