Only a short muscle growth response to BCAAs?

Are BCAAs effective for muscle growth?

Dietary protein provides amino acids as building blocks for muscle tissue. Branched-chain amino acids (BCAAs) are a subclass of amino acids that have potent anabolic properties. Therefore, BCAAs are popular supplements. However, should you take BCAAs in supplemental form or just consume them as part of complete protein?

This study investigated the effect of 6 g BCAAs, 6 g branched-chain keto acids (BCKAs), and 30 g milk protein (which contains 6 g BCAAs) on muscle protein synthesis in older men. BCKA’s are similar to BCAAs, but do not contain nitrogen.

BCAAs, BCKAs, and milk protein all stimulated muscle protein synthesis to the same extent in the first two hours after ingestion.

However, the muscle protein synthetic response remained elevated longer in the milk protein group compared to the BCAAs and BCKAs groups.

Therefore, it seems that BCAAs can stimulate muscle protein synthesis, but only for a short period of time. However, the fact that BCKAs can stimulate muscle protein synthesis might have applications for patients prescribed a low nitrogen diet (e.g. kidney patients).  

Study:
Fuchs et al. Branched-chain amino acids and branched-chain ketoacid ingestion increase muscle protein synthesis rates in vivo in older males. Am J Clin Nutr. 2019

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