BCAA Amino acids are branched chain amino acids (leucine, valine and isoleucine) that are used as substrates to produce protein. They are typically found in proteins such as egg, fish, red meat and dairy products but also can be taken as a supplement. BCAA are important as they promote muscle protein synthesis and prevent the breakdown of muscle tissue during periods of inactivity.

They can be consumed at any time but are most effective pre-workout to increase energy and reduce fatigue, during exercise to reduce muscle damage and speed up recovery and post-training to help rebuild muscles that have been damaged. BCAA supplements are often available in powdered form, which can be mixed with water or a drink according to manufacturer instructions. They are also found in many foods such as chicken, eggs, fish, red meat, dairy products and soy proteins.

While some research has shown that BCAA supplements can increase muscle protein synthesis, there is limited evidence that they have an anabolic effect in human subjects. The reason for this is that the supply of EAAs via BCAA supplementation must overcome the negative balance between protein synthesis and protein breakdown to exert an anabolic effect. In the experiments cited above in which BCAAs were infused intravenously to stimulate muscle protein synthesis, there was no change in activation of the initiation factors and the net rate of protein synthesis decreased due to lack of EAA availability resulting from a decrease in protein breakdown.

Moreover, the assumption that the consumption of a mixture of BCAAs produces anabolic effects is flawed because there are no data on the response to individual BCAAs. In fact, when a mixture of BCAAs was administered to humans along with carbohydrate the rate of muscle protein synthesis decreased to the same level as in the control group. This indicates that the unique anabolic effect of BCAAs is not due to their individual contributions to the supply of EAAs for muscle protein synthesis but rather to the fact that they improve the efficiency with which the EAAs can be recycled from the degradation of other proteins.

In the long term, BCAAs may help to maintain muscle mass in chronic conditions that can lead to a loss of lean body mass such as diabetes. However, further research is required to establish the clinical validity of this potential benefit of consuming a high-protein diet that is rich in BCAAs. In addition, the interaction of BCAA metabolism with glucose and lipid metabolism in different tissues of the host and the gut microbiota needs to be better understood. This is crucial to avoid a biased picture of the role of BCAAs in muscle protein synthesis that may mislead efforts for developing novel therapeutic strategies.