Should You Be Supplementing with Branched Chain Amino Acids?

Trendy supplements used by athletes today are branched chain amino acids (BCAA).  These proteins include leucine, isoleucine and valine.  Athletes are using these with the intent of improving performance through reduced protein turnover and muscle breakdown during exercise.

BCAAs are present in our amino acid pool located in our blood.  To keep the levels of BCAAs maintained during endurance exercise, protein breakdown from the muscles is necessary. However, the oxidation of BCAAs in skeletal muscle often exceeds their supply from protein during prolonged exercise. This results in the BCAAs being taken from our pool, decreasing concentrations in the blood to maintain adequate amounts in our muscles (Ohtani,2006).

As concentrated levels of BCAAs decrease, an increase of tryptophan is present in the blood- brain barrier.  BCAA and tryptophan share the same binding site in the brain.  When BCAA are limited, the tryptophan increases binding at this site.  This switched binding is often associated with fatigue in athletes. This is because an uptake of tryptophan across the blood–brain barrier increases serotonin formation in the brain.  Increased serotonin results in a fatigue termed central fatigue.

Also associated with central fatigue is an increase of free fatty acids delivered to the muscles for energy during exercise.  Thus, the ratio of fat in the muscle increases while the amino acid concentration is decreasing, creating an imbalance.  Tryptophan levels are also affected due to this.  Tryptophan increases because as free fatty acids rise in the muscles, tryptophan is displaced from binding to albumin, creating free tryptophan, which can then easily be transported and bind in the brain and again increase serotonin levels to increase fatigue. (Gleeson, 2005). Talk about a double threat! 

The theory that BCAA supplementation can correct fatigue in athletes is that the pool of BCAAs will be greater, therefore decreasing the drop in plasma BCAAs.  This will not throw off the tryptophan: BCAA ratio, which will not effect serotonin levels in the brain, therefore decreasing risk for central fatigue.  However, this is not the reasoning behind why many athletes are taking these supplements.  They plan on reducing the actual breakdown of muscle during exercise; while the theory is increasing BCAA in the amino acid pool to help decrease plasma concentration loses.

Although this concept seems promising there are always risks to be taken when consuming any supplement, especially as they are poorly regulated.  Although nothing too serious has been found yet related to BCAA supplementation, some specific risks of taking BCAA include nausea, pain and headaches.  When looking at the brand Optimum Nutrition, one can get 400 capsules for $27.29.  Each capsule contains 500mg L-Leucine, 250mg L-Isoleucine, and 250mg L-Valine for a total of 1000mg of BCAAs.  The serving size is 2 capsules, which would provide 2000mg/day.  Therefore it is not terribly expensive seeing a bottle would last a little over 6 months.  Compare this price to other protein supplements that may not be as concentrated in the BCAA, and you can see this is a reasonable supplement to consider when looking to increase your protein consumption.

Ohtani M, Sugita M, Maruyama K. Amino Acid Mixture Improves Training Efficiency in Athletes. Journal Of Nutrition [serial online]. February 2006;136(2):538S-543S. Available from: Academic Search Complete, Ipswich, MA. Accessed October 26, 2015.

Gleeson M. Interrelationship between Physical Activity and Branched-Chain Amino Acids. Journal Of Nutrition [serial online]. June 2, 2005;135:1591S-1595S. Available from: Academic Search Complete, Ipswich, MA. Accessed October 26, 2015.

BCAA 1000 Caps.  BodyBilding.  Updated 2015.  Accessed October 26, 2015.


  1. Andrew says:

    Would you recommend using BCAA for a sport performance supplement? If so, when would you say is the best time to use them in order to increase performance?


    • Hey! Thanks for the great question. I would recommend using the BCAA supplement prior to your workout. As mentioned in the article, the mechanism of this supplement is that it can build up in the blood and decrease the breakdown of proteins during your work out. Getting a good portion in about an hour or two prior to your workout should show benefits!


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