Branched Chain Amino Acids – BCAAs for short – are commonly taken by athletes who are trying to improve their performance in the gym and on the field. These products often claim that they will boost muscle growth and enhance performance, and as a result there is a multi-million-dollar industry that has been built around BCAA supplements alone. However, closer examination of the research reveals that they may not be as helpful as many think.
Protein provides the structure of cells, muscles, organs, and virtually every other tissue in the body while also playing a crucial role in nutrient transport, hormone regulation, and the immune system. Thus, it is a fundamental and crucial element of human nutrition. In the athlete population, the need for protein is even greater, as adequate protein intake is a necessity for optimizing muscle growth, as well as promoting muscle repair and prevention of muscle breakdown – all key factors for any successful athlete.
Breaking down protein into a little more detail, athletes should understand that amino acids serve as the building blocks for proteins. There are 20 basic amino acids that function in a variety of ways, and they are separated into two groups, non-essential and essential. Non-essential amino acids can be synthesized by the body without any dietary intake. Essential amino acids cannot be synthesized by the body and must be obtained from dietary sources. There are three branched chain amino acids – Leucine, Isoleucine, and Valine – which are all essential amino acids. The BCAAs are grouped together because of their structure, which contains a unique side chain branching off, a trait which all the other amino acids do not have. When proteins are comprised of one or more chains of amino acids, they are called polypeptides.
Unlike all other amino acids, BCAAs are metabolized in skeletal muscle (Koo, et al., 2014). Consequently, stimulation of protein synthesis in skeletal muscle in response to feeding is largely because of BCAAs. Of the three BCAAs, it has been determined that leucine is primarily responsible for the stimulation of muscle protein synthesis (Kimball, et al, 2006). Considering this, it’s understandable that one might assume that consumption of a BCAA supplement high in leucine would further enhance this muscle building process. However, current research does not support this idea.
In September of 2022, a systematic review of recent scientific literature was published by Martinho, et al, reviewing the potential impact that oral ingestion of BCAAs may have on performance, body composition, recovery, biochemical processes, hormonal response and/or molecular signaling in an athlete-specific population. Analysis of the literature concluded that “BCAA supplementation has minimal impact on performance and negligible effects on body composition.” However, there were instances in which the addition of a BCAA supplement yielded benefits; the results of two studies, in which resistance-trained individuals used a 70% 1RM-based muscle damaging exercise session and were given supplementation over a relatively short period of time, suggest that “oral ingestion of isolated BCAAs reduces muscle soreness,” particularly in resistance athletes.
While BCAAs – more specifically, leucine – do stimulate muscle protein synthesis, the muscle building process requires the full spectrum of essential amino acids to be carried out. Taking only BCAAs is essentially similar to baking a cake using only flour and no other ingredients. Instead, athletes would benefit more by utilizing a more complete approach instead of relying on supplementation; eating 20 – 40g of high quality protein would provide 10-12g of essential amino acids, as well as the 1-3g of leucine needed to stimulate muscle protein synthesis. (Jager et al, 2017). Provided that total protein intake requirements are met, the benefits of supplementing with additional BCAAs appear to be minimal. Additionally, for athletes in a calorie deficit that may be interested in supplementing with BCAAs to preserve muscle mass, the latest research suggests that the supplement is ineffective here as well. Ooi, et al, determined that the effects of supplementation with BCAAs in a hypocaloric state did not have a significant effect on preservation of lean body mass, and instead concluded that a higher protein diet was the most effective solution.
The easiest and most accessible way to get all EAAs is through a balanced diet. Some examples of foods that contain all essential amino acids, including the BCAAs, are beef, eggs, fish, poultry, dairy, and soy. Foods that do not contain all EAAs are known as incomplete proteins. Examples of these include nuts, seeds, beans and some grains. Those following a plant-based diet may need to be more diligent in combining several types of incomplete proteins to ensure they are getting an optimal spread of all 9 EAAs.
For athletes striving to achieve their body composition goals and improve strength-related performance, their focus should be on ensuring they are consistently including protein sources that are rich in all essential amino acids, as well as meeting an appropriate daily protein goal of ≥1.6 g/kg/day. Within the context of those daily recommendations, athletes should strive to consume a post-exercise recovery snack or meal including 0.25g – 0.3 g/kg of a high-quality protein source. (Beelen, 2010) This looks like 14g – 16g for a 120 lb athlete and 23g – 27g for a 200lb athlete. Though these are good guidelines to follow, an athlete interested in an individualized plan specific to their unique needs should seek out a Registered Dietitian who can help them reach their goals.
In the case of BCAA’s, the research suggests that athletes would be better served saving their money and investing their time and energy toward their overall nutrition to achieve optimal results. If an athlete is unable to meet their protein needs through whole foods, a third-party tested protein supplement can be a helpful tool. Whey protein is an appropriate option as it contains all essential amino acids, including BCAAs.
Considering this recommendation to opt for whole food protein sources when possible, athletes and practitioners alike should each keep in mind that the supplement industry is not regulated by the FDA, so there is inherent risk associated with taking any supplement. If an athlete does want to support their daily whole food intake with a supplement they should look for options that have been third-party tested for purity by a reputable agency such as NSF Certified for Sport or Informed Sport to be sure that what they think they’re taking is what is truly in the package. If an athlete is considering taking supplements, encourage them to ask themselves the following questions: Is the supplement legal? Is it safe? Will it be effective (i.e., Is there science to prove it works or is it a waste of my money?)? In the case of BCAA supplements, there just isn’t enough conclusive evidence to say they are worth taking.
Beelen, Milou, et al. “Nutritional Strategies to Promote Postexercise Recovery.” International Journal of Sport Nutrition and Exercise Metabolism, vol. 20, no. 6, 2010, pp. 515–532., https://doi.org/10.1123/ijsnem.20.6.515.
Jäger, Ralf, et al. “International Society of Sports Nutrition Position Stand: Protein and Exercise.” Journal of the International Society of Sports Nutrition, vol. 14, no. 1, 2017, https://doi.org/10.1186/s12970-017-0177-8.
Kimball SR, Jefferson LS. Signaling pathways and molecular mechanisms through which branched-chain amino acids mediate translational control of protein synthesis. J Nutr. 2006 Jan;136(1 Suppl):227S-31S. doi: 10.1093/jn/136.1.227S. PMID: 16365087.
Koo GH, Woo J, Kang S, Shin KO. Effects of supplementation with BCAA and L-glutamine on blood fatigue factors and cytokines in juvenile athletes submitted to maximal intensity rowing performance. J Phys Ther Sci. 2014;26:1241–1246.
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Ooi, Delicia S, et al. “Branched-Chain Amino Acid Supplementation Does Not Preserve Lean Mass or Affect Metabolic Profile in Adults with Overweight or Obesity in a Randomized Controlled Weight Loss Intervention.” The Journal of Nutrition, vol. 151, no. 4, 2021, pp. 911–920., https://doi.org/10.1093/jn/nxaa414.