Branched-Chain Amino Acids…Helpful or Hype?

By: Jeremy Partl, Registered Dietitian

When it comes to muscle building and body recomposition, there are not many more popular supplements than branched-chain amino acids (BCAAs). Beyond boring old whey protein, this niche product is supposedly the holy grail of building slabs of muscle, helping to shred every ounce of fat and get you jacked. Does spending twice as much really amplify the gains?

In this article, I am going to cover the basics of what BCAAs are and dive deeper into the research to give you an evidence-based perspective on whether or not BCAAs are worthy of purchase and what I like to recommend to clients.

Protein, Branched-Chain Amino Acids, and Building Muscle: A Primer

Proteins are made of amino acids. Of the 20 amino acids found in the human body, nine of those amino acids are considered essential because they cannot be synthesized by the body. Within that select group, three of the essential amino acids are referred to as branched-chain amino acids—as you could have guessed, because of their structure. The three BCAAs are leucine, isoleucine, and valine.

What makes BCAAs unique is that they are primarily metabolized within the muscle, as opposed to being broken down by the liver.[1] What this means for us practically is that:

• BCAAs can provide an additional fuel source for working muscle during prolonged exercise.[2]
• BCAAs help regulate whether the body is in an anabolic (tissue building) or catabolic (tissue breakdown) state.[3]

Building muscle mass is the end result of net protein balance, driven by increases in muscle protein synthesis (MPS) exceeding muscle protein breakdown (MPS > MPB). With regards to nutrition, MPS is increased by protein ingestion and the signaling cascade that happens in the muscle cells. Primary to this cascade of protein synthesis is the mechanistic target of rapamycin (mTOR), which acts as a nutrient sensor that is largely influenced by leucine—one of the BCAAs.

Based on the available evidence, it seems that it takes two to three grams of leucine to reach a trigger level necessary for maximal stimulation of MPS, below which maximal stimulation fails to occur.[4] It’s like a light switch: if you get enough leucine, you “flip the switch” on MPS. Depending on factors such as exercise habits and routine, energy status, body weight, and potential level of muscularity, it appears the optimal dose of high-quality protein for stimulating muscle protein accretion is likely between 20 and 40 grams at a single feeding. [5],[6]

Most of the literature shows that beyond a certain threshold of leucine and total protein

intake, there is no further benefit to the MPS response. However, only recently has it been observed that there can be a greater MPS to a 70-gram dose of protein (versus 35 grams), although this needs to be replicated and not confounded by resistance training.[7]

Potential Benefits of Taking BCAAs

Fatigue during exercise can be attributed to fatigue substances (lactate and ammonia), energy metabolites (glucose and free fatty acids), muscle soreness substances (LDH and CK), and neurotransmitters and hormones (such as 5-HTP and serotonin).[8] A 2019 review has found that as a nutritional supplement, BCAAs may have beneficial effects on markers of lactate, FFA, glucose, ammonia, and CK, resulting in inhibition of fatigue and the ability to sustain exercise for longer periods of time. There did not seem to be a positive impact on central fatigue (the neurotransmitters and hormones) and LDH, which makes the case for prolonging exercise a bit weaker.

In addition, studies using BCAAs have shown that supplementation leading up to a graded exercise test to exhaustion (whether over the week leading up to the test or just an hour before) can improve VO2max, VO2 at the lactate threshold, power output, and time to exhaustion.[9],[10] (Matsumoto et al., 2009).

There has also been a study showing that ten weeks of BCAA supplementation (12 grams/day) resulted in increases in all-out sprint peak power and average power relative to body mass, although it’s unclear if or how the improvements in anaerobic performance may necessarily translate much to strength training and overall strength measures.[11]

Thus, it’s very likely that BCAAs have a positive effect on both aerobic and anaerobic performance. However, these benefits primarily relate to prolonged exercise sessions and endurance-based events. Unless you are doing fasted cardio or multiple hour-long bodybuilding sessions, it’s unlikely that you will see much out of these benefits.

Building Muscle

Although it mechanistically makes sense that BCAAs could help to influence gains in muscle mass, research largely shows that there are no additional benefits to BCAA supplementation when sufficient energy and protein intake are in place.[12]

If there is sufficient intake, there is more than likely sufficient leucine to fully stimulate the MPS response, even in the case of older adults who may need greater amounts (~3 grams) to reach leucine thresholds.[13],[14]

However, taking BCAAs alone, even though they contain the leucine necessary to stimulate the pathways for MPS, may not be optimal for a variety of reasons.

1. The full scope of essential amino acids is still limited (Jackman et al., 2017).
2. Isoleucine and valine may compete with leucine for transport into the muscle cell (Churchward-Venne et al., 2014).

One case where BCAAs may actually be useful is when there is inadequate protein intake. In situations where there is not a whole protein source or sufficient essential amino acid availability, a higher dose of leucine or other nutrients can help to rescue the MPS response.[15]

For example, research from Tipton and colleagues found that consuming 16.6 grams of whey protein with 3.4 grams of leucine had the same net protein balance as those who ingested 20 grams of whey protein alone.[16] Furthermore, supplementation of leucine and carbohydrate in addition to an inadequate dose of whey protein with carbohydrate was effective in stimulating MPS.[17]

This could be a beneficial finding for plant-based eaters who may not be reaching the 2-3 gram trigger of leucine with each meal. By taking supplemental BCAAs, it may provide enough leucine to help rescue the MPS response.

Improved Strength

Very similar to the evidence in the area of muscle hypertrophy, BCAA supplementation lacks efficacy for improving strength performance in a large number of studies.[18] It seems that studies in which there have been small beneficial impacts on strength were confounded by inadequate protein or calorie intake.[19],[20]

While there is good data showing that BCAAs may reduce exercise-induced muscle damage (suggesting a potential benefit to muscle recovery), the literature has not found meaningful improvements in performance outcomes.[21]

Sparing Muscle Mass

There is a very small amount of evidence that suggests that BCAA supplementation may help to minimize muscle loss during periods of weight loss/energy restriction.[22],[23] However, it is questionable whether or not the results of the primary study showing a beneficial effect of maintaining lean muscle mass would have shown similar results with intact, high-quality protein supplementation.[24],[25]

A Better Alternative?

To summarize all of this, here is a quote from the latest review on the topic from the highly recognized International Journal of Sport Nutrition and Exercise Metabolism.[26]

“Given the current evidence, the majority of the literature fails to support BCAA supplements as ergogenic aids in the context of strength and hypertrophy. Importantly, longitudinal studies largely fail to support the efficacy of BCAA supplementation provided sufficient daily protein is ingested.”

What really matters for muscle building and retention is adequate amounts of essential amino acids and a signal that tells the body to favor synthesis over metabolism.

There are only a few cases where I might suggest supplementation with BCAAs.

• In cases where you are not getting enough protein and amino acids at a meal (although occasionally lacking enough protein is not significant in the larger picture of things)
• If calorie intake is severely low (although I would still recommend whole intact proteins)
• If you want to spend money unnecessarily

Instead of relying on BCAA supplements, high-quality, intact proteins provide the full complement of essential amino acids and, if contained as a whole food, will be ingested with other constituents (such as dairy exosomes, fats, or undetermined properties in eggs) that could even further increase the anabolic response.[27],[28],[29]

If you are going to supplement, it would be best to just get a quality whey (or plant-based) protein powder. You could spend extra money on EAAs or BCAAs, but it likely will not give you any additional benefits.

Notes

^[1] Tom, A., & Nair, K. S. (2006). Branched-chain amino acids: metabolism, physiological function, and application. Biomarkers, 1, 3.

^[2] Shimomura, Y., Murakami, T., Nakai, N., Nagasaki, M., & Harris, R. A. (2004). Exercise promotes BCAA catabolism: effects of BCAA supplementation on skeletal muscle during exercise. The Journal of nutrition, 134(6), 1583S-1587S.

^[3] Shimomura, Y., Murakami, T., Nakai, N., Nagasaki, M., & Harris, R. A. (2004). Exercise promotes BCAA catabolism: effects of BCAA supplementation on skeletal muscle during exercise. The Journal of nutrition, 134(6), 1583S-1587S.

^[4] Breen, L., & Phillips, S. M. (2012). Nutrient interaction for optimal protein anabolism in resistance exercise. Current Opinion in Clinical Nutrition & Metabolic Care, 15(3), 226-232.

^[5] Macnaughton, L. S., Wardle, S. L., Witard, O. C., McGlory, C., Hamilton, D. L., Jeromson, S., … & Tipton, K. D. (2016). The response of muscle protein synthesis following whole‐body resistance exercise is greater following 40 g than 20 g of ingested whey protein. Physiological reports, 4(15).

^[6] 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(1), 1-6.

^[7] Park, S., Jang, J., Choi, M. D., Shin, Y. A., Schutzler, S., Azhar, G., … & Kim, I. Y. (2020). The anabolic response to dietary protein is not limited by the maximal stimulation of protein synthesis in healthy older adults: a randomized crossover trial. Nutrients, 12(11), 3276.

^[8] Hormoznejad, R., Javid, A. Z., & Mansoori, A. (2019). Effect of BCAA supplementation on central fatigue, energy metabolism substrate and muscle damage to the exercise: a systematic review with meta-analysis. Sport Sciences for Health, 15(2), 265-279.

^[9] Branched-chain amino acid supplementation increases the lactate threshold during an incremental exercise test in trained individuals.

^[10] AbuMoh’d, M. F., Matalqah, L., & Al-Abdulla, Z. (2020). Effects of Oral Branched‐Chain Amino Acids (BCAAs) Intake on Muscular and Central Fatigue During an Incremental Exercise. Journal of human kinetics, 72, 69.

^[11] Kephart, W. C., Wachs, T. D., Mac Thompson, R., Mobley, C. B., Fox, C. D., McDonald, J. R., … & Roberts, M. D. (2016). Ten weeks of branched-chain amino acid supplementation improves select performance and immunological variables in trained cyclists. Amino Acids, 48(3), 779-789.

^[12] Plotkin, D. L., Delcastillo, K., Van Every, D. W., Tipton, K. D., Aragon, A. A., & Schoenfeld, B. J. (2021). Isolated Leucine and Branched-Chain Amino Acid Supplementation for Enhancing Muscular Strength and Hypertrophy: A Narrative Review. International Journal of Sport Nutrition and Exercise Metabolism, 31(3), 292-301.

^[13] Koopman, R., Walrand, S., Beelen, M., Gijsen, A. P., Kies, A. K., Boirie, Y., … & van Loon, L. J. (2009). Dietary protein digestion and absorption rates and the subsequent postprandial muscle protein synthetic response do not differ between young and elderly men. The Journal of nutrition, 139(9), 1707-1713.

^[14] Pennings, B., Groen, B., de Lange, A., Gijsen, A. P., Zorenc, A. H., Senden, J. M., & Van Loon, L. J. (2012). Amino acid absorption and subsequent muscle protein accretion following graded intakes of whey protein in elderly men. American Journal of Physiology-Endocrinology and Metabolism, 302(8), E992-E999.

^[15] Plotkin, D. L., Delcastillo, K., Van Every, D. W., Tipton, K. D., Aragon, A. A., & Schoenfeld, B. J. (2021). Isolated Leucine and Branched-Chain Amino Acid Supplementation for Enhancing Muscular Strength and Hypertrophy: A Narrative Review. International Journal of Sport Nutrition and Exercise Metabolism, 31(3), 292-301.

^[16] Tipton, K. D., Elliott, T. A., Ferrando, A. A., Aarsland, A. A., & Wolfe, R. R. (2009). Stimulation of muscle anabolism by resistance exercise and ingestion of leucine plus protein. Applied Physiology, Nutrition, and Metabolism, 34(2), 151-161.

^[17] Churchward‐Venne, T. A., Burd, N. A., Mitchell, C. J., West, D. W., Philp, A., Marcotte, G. R., … & Phillips, S. M. (2012). Supplementation of a suboptimal protein dose with leucine or essential amino acids: effects on myofibrillar protein synthesis at rest and following resistance exercise in men. The Journal of physiology, 590(11), 2751-2765.

^[18] Plotkin, D. L., Delcastillo, K., Van Every, D. W., Tipton, K. D., Aragon, A. A., & Schoenfeld, B. J. (2021). Isolated Leucine and Branched-Chain Amino Acid Supplementation for Enhancing Muscular Strength and Hypertrophy: A Narrative Review. International Journal of Sport Nutrition and Exercise Metabolism, 31(3), 292-301.

^[19] Rondanelli, M., Opizzi, A., Antoniello, N., Boschi, F., Iadarola, P., Pasini, E., … & Dioguardi, F. S. (2011). Effect of essential amino acid supplementation on quality of life, amino acid profile and strength in institutionalized elderly patients. Clinical nutrition, 30(5), 571-577.

^[20] Kim, H. K., Suzuki, T., Saito, K., Yoshida, H., Kobayashi, H., Kato, H., & Katayama, M. (2012). Effects of exercise and amino acid supplementation on body composition and physical function in community‐dwelling elderly Japanese sarcopenic women: a randomized controlled trial. Journal of the American Geriatrics Society, 60(1), 16-23.

^[21] Plotkin, D. L., Delcastillo, K., Van Every, D. W., Tipton, K. D., Aragon, A. A., & Schoenfeld, B. J. (2021). Isolated Leucine and Branched-Chain Amino Acid Supplementation for Enhancing Muscular Strength and Hypertrophy: A Narrative Review. International Journal of Sport Nutrition and Exercise Metabolism, 31(3), 292-301.

^[22] Plotkin, D. L., Delcastillo, K., Van Every, D. W., Tipton, K. D., Aragon, A. A., & Schoenfeld, B. J. (2021). Isolated Leucine and Branched-Chain Amino Acid Supplementation for Enhancing Muscular Strength and Hypertrophy: A Narrative Review. International Journal of Sport Nutrition and Exercise Metabolism, 31(3), 292-301.

^[23] . In a single-blind,

matched group design: Branched-chain amino acid supplementation

and resistance training maintains lean body mass during a caloric

restricted diet

^[24] . In a single-blind,

matched group design: Branched-chain amino acid supplementation

and resistance training maintains lean body mass during a caloric

restricted diet

^[25] Mettler, S., Mitchell, N., & Tipton, K. D. (2010). Increased protein intake reduces lean body mass loss during weight loss in athletes. Med Sci Sports Exerc, 42(2), 326-37.

^[26] Plotkin, D. L., Delcastillo, K., Van Every, D. W., Tipton, K. D., Aragon, A. A., & Schoenfeld, B. J. (2021). Isolated Leucine and Branched-Chain Amino Acid Supplementation for Enhancing Muscular Strength and Hypertrophy: A Narrative Review. International Journal of Sport Nutrition and Exercise Metabolism, 31(3), 292-301.

^[27] Burd, N. A., Beals, J. W., Martinez, I. G., Salvador, A. F., & Skinner, S. K. (2019). Food-first approach to enhance the regulation of post-exercise skeletal muscle protein synthesis and remodeling. Sports medicine, 49(1), 59-68.

^[28] Elliot, T. A., Cree, M. G., Sanford, A. P., Wolfe, R. R., & Tipton, K. D. (2006). Milk ingestion stimulates net muscle protein synthesis following resistance exercise. Medicine & Science in Sports & Exercise, 38(4), 667-674.

^[29] Bagheri, R., Moghadam, B. H., Ashtary-Larky, D., Forbes, S. C., Candow, D. G., Galpin, A. J., … & Wong, A. (2021). Whole egg vs. egg white ingestion during 12 weeks of resistance training in trained young males: A randomized controlled trial. The Journal of Strength & Conditioning Research, 35(2), 411-419