A common supplement amongst gym-goers are branch chain amino acids (BCAAs). Supplement companies have pushed the benefits to include enhanced hydration, recovery and increased muscle building. Couple those benefits with a great flavor and its no wonder why BCAAs alone are a multi-million dollar seller. Early in my personal training career I bought into the hype, used them myself and told my clients that they should too. But were the purported benefits legitimate? Within this article I’ll specifically delve into what current research has shown specifically to increased muscle gain.
Muscle protein has 22 amino acids, and 9 of those are called essential amino acids (EAAs) since we don’t produce them in our bodies in any significant amount. Therefore it is very important that we include them in our diet. Our bodies are constantly turning over protein. Protein synthesis is crucial to replace old protein that breaks down and is happening to some degree at all times. In order to synthesize new muscle protein, all EAAs and non-essential amino acids (NEAAs) need to be present, and in adequate amounts (Wolfe, 2017). The BCAAs are leucine, isoleucine, and valine are 3 of the 9 EAAs and leucine especially is thought to play a significant role as a precursor to muscle protein synthesis (MPS) and signaling pathways involved in the process.
As early as 1981 a study was conducted that concluded that the presence of BCAAs might be what limits MPS in rats (Buse, 1981). Other studies showed small effects on rats but there are many differences between humans and rats that make so that these findings can’t be inferred. One marked difference is that MPS in rats seem to be limited by the initiation process rather than the translation process as in humans (Wolfe, 2017). This, along with other differences render rat studies to be mostly inapplicable to humans in regards to BCAAs.
As mentioned, our bodies are constantly turning over protein. Synthesizing protein at a rate faster than the rate of degradation is referred to as an “anabolic state.” In order to accumulate muscle protein we need to net more anabolism than catabolism (state of protein loss). In addition to increasing the rate of MPS, decreasing the rate at which proteins are being broken down could also tip the scales towards anabolism (Wolfe, 2017). But in order to significantly stimulate MPS, EAAs need to be present in large quantities (eating a balanced protein meal). Since NEAAs can be produced in our body, EAAs are also the rate limiting factor for MPS. Interestingly, EAAs can not only be pulled from what we eat, but small amounts can actually be recycled from the degraded protein (Wolfe, 2017). This is because once the available quantity of EAAs starts to diminish, our muscle stops intaking EAAs and actually starts releasing them into the plasma to help other tissues maintain their rate of protein synthesis, and is referred to as the post-absorptive state (Wolfe, 2017).
If BCAAs could cause anabolism during this post-absorptive state where only the recycled EAAs are present in the plasma then supplement companies would surely have a golden product. But research has shown that in this state, our bodies are breaking down protein at a rate 30% faster than it is being synthesized (Biolo et al., 1994). As a reminder, all 9 EAAs are required to make protein. So if we only ingest 3 (BCAAs) then the only place to pull the other 6 from are whats being recycled from broken down muscle protein. This creates a situation where its theoretically impossible to reach a state of anabolism (Wolfe, 2017). Because if we have to wait for a muscle protein to be broken down before we can create a new one, then how are we ever going to produce more proteins than are being broken down? At best, Wolfe (2017) estimates that BCAAs can reduce the rate of muscle protein breakdown by 15%. This is far from anabolic.
This does not render BCAAs completely useless. A meta-analysis by Fedewa et al. (2019) showed that BCAA supplementation reduces muscle soreness after resistance training. Muscle soreness can definitely be annoying and may be particularly limiting during a time period of functional overreaching. Perhaps including BCAAs during this time period could help athletes recover faster in order to have better consecutive workouts. This small reduction to muscle soreness may justify the heavy price tag for some lifters, but may not be worth it to others.
If the goal is to increase muscle mass then I would not suggest spending the money on BCAAs. Although leucine is shown to be stimulatory of MPS, research by Hulmi et al. (2010) showed that whey protein had a greater effect on MPS than leucine alone or other protein types. Before looking to any supplement I would suggest taking a look at the basics. Following an exercise program that implements simple principles such as progressive overload and training specificity will do far more for progress to hypertrophy (Haff & Triplett, 2016). Also, following sound guidelines in relation to protein intake has been studied to increase anabolism (Schoenfeld & Aragon, 2018) and will likely produce far more significant results than BCAA supplementation.
Biolo, G., Gastaldelli, A., Zhang, X. J., Wolfe, R. R. (1994). Protein synthesis and breakdown in skin and muscle: A leg model of amino acid kinetics. American Journal of Physiology-Endocrinology and Metabolism, 30, 464-474.
Buse, M. G. (1981). In vivo effects of branched chain amino acids on muscle protein synthesis in fasted rats. Hormone and Metabolic Research, 13, 502-505.
Haff, G. & Triplett, N. (2016). Essentials of strength and conditioning (4th Edition). Champaign, IL: Human Kinetics.
Hulmi, J. J., Lockwood, C. M., & Stout, J. R. (2010). Effect of protein/essential amino acids and resistance training on skeletal muscle hypertrophy: A case for whey protein. Nutrition & Metabolism, 7, 51-61.
Schoenfeld, B. J., & Aragon, A. A. (2018). How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. Journal of the International Society of Sports Nutrition, 15(10).
Wolf, R. R. (2017). Branched-chain amino acids and muscle protein synthesis in humans: myth or reality? Journal of the International Society of Sports Nutrition, 14(30).