Proteins are made up of smaller units called amino acids. There are 20 different amino acids – 11 non-essential, those that the body can produce on its own, and 9 essential, the ones the body can’t produce and are mostly obtained through food. BCAA (branched chained amino acids) are 3 amino-acids that are said to play the most important role in muscle growth. EAA (essential amino acids) are a combination of all 9 essential amino acids, including those 3 in BCAA. The sale of BCAA as nutritional supplements has become a multi-million-dollar business. It is a widely-believed claim that consumption of BCAA after training stimulates muscle protein synthesis.
What is Muscles Protein Synthesis?
Muscle protein synthesis is a process where new protein is being produced, the key process of muscle growth. A process taking place at the same time is the protein breakdown. One looking to gain muscle mass would want the synthesis to exceed the breakdown, this state is called anabolic state. BCAA is said to maximize the anabolic state by further stimulating the muscle protein synthesis.
Previous claims that BCAA stimulates muscle protein synthesis are obtained from studies of the response in rats, and often BCAA in combination with other substances like insulin. Kobayashi et al. (1) injected rats with just BCAA and found that although it slightly stimulated their muscle protein synthesis, the process was strongly dependent on the availability of the other essential amino acids, EAA. EAA can’t be produced in the body, and therefore we either need to get EAA from foods/supplements or our bodies break down existing proteins to release EAAs (i.e. during protein breakdown).
What Happens When You Take BCAAs?
Just taking BCAA hasn’t been able to increase the muscle protein synthesis in humans, but it HAS been shown to decrease protein breakdown instead (2-3). This would, in turn, reduce the availability of EAA within the muscle cells and the protein synthesis would, therefore, be impaired.
In other words, consuming BCAA after training or between meals is of course better than doing nothing, this would at least decrease the protein breakdown a little bit. However, EAA is a better choice in this matter supporting both the protein synthesis and breakdown, hence, maximizing the muscle growth.(4)
Article by Maria Ekblom, licensed physiotherapist and personal trainer.
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