Are BCAAs worth it for building muscle?

What are BCAAs?

BCAAs (branched-chain amino acids) are the three essential amino acids leucine, isoleucine, and valine. Leucine is considered the primary trigger of muscle protein synthesis via the mTOR signaling pathway. The fitness industry markets BCAAs as an ergogenic supplement for promoting muscle growth and recovery. The scientific evidence, however, paints a more nuanced picture.

What the research shows

In a widely cited paper in the Journal of the International Society of Sports Nutrition, Wolfe (2017) argued that BCAAs alone cannot maximally stimulate muscle protein synthesis, because building new muscle protein requires all 20 proteinogenic amino acids. Supplying just three of them in isolation limits synthesis, since the remaining essential amino acids are missing.

Jackman et al. (2017) confirmed this experimentally: BCAAs did raise muscle protein synthesis by 22% above the resting value, but a complete protein (whey) produced a 50% greater increase. In their position stand, the ISSN (Jäger et al., 2017) states that at a daily protein intake of at least 1.6 g/kg, no additional BCAA supplementation is necessary.

When might BCAAs make sense?

One possible exception is people who can't meet their protein needs from complete protein sources — for example, those eating very little during an aggressive diet, or following certain restricted eating patterns. In practice this is a very small group. For most people who train, total protein intake and the overall structure of the diet matter far more.