In brief

  • The amino acids leucine, valine, and isoleucine comprise the branched-chain amino acids (BCAAs)
  • As one of the best-studied dietary supplements, research-proven benefits of BCAAs include stimulation of muscle growth, sparing muscle mass/promoting of fat loss during weight loss diets, reduction in muscle soreness and aiding recovery after intense training, and protecting immune function
  • BCAAs are essential in an athletes diet to maximise gains from training and enhancing recovery


Protein is a key macronutrient in an athlete’s diet. Aside from the importance of how much protein is consumed on a daily basis (which is intensely debated), an increasing body of evidence suggests that the timing of protein intake around training sessions provides numerous benefits in terms of improving training outcomes including enhancing recovery time, and maintaining or even increasing muscle mass 1. Each individual protein within the body and diet are made up of long chains of building blocks known as "amino acids" (AAs). These chains of AAs are known as polypeptides, and it is these polypeptides that make up an individual protein.

Of the ~20 standard amino acids, a subset of 9 of these are considered essential amino acids (EAA), meaning that they cannot be produced within the body itself, and therefore are obtained from dietary sources (in particular, from animal products such as meat and dairy). A further subset of these EAAs is the "branched-chain" amino acid group, which consists of three AAs namely leucine, isoleucine and valine.

Since the mid-1990s, a large amount of research has focussed on the apparent ability of BCAAs to stimulate muscle growth (technically known as "muscle protein synthesis"), both in athletic populations and in disease states such as surgery, aging and muscle wasting. The weight of evidence strongly suggests that the ingestion of AAs (and in particular BCAAs) prior to, during and immediately after strength training (and to a lesser extent with aerobic training) can enhance the gains that athletes achieve from training in terms of gaining muscle mass and promoting fat loss. This article will briefly summarise this evidence. The broader role of general protein intake in the athlete’s diet is covered on our article on "Protein needs for athletes".

What are BCAAs, and what is their role in exercise metabolism?

BCAAs are so-called because of their chemical structure when compared to other amino acids. Every amino acid has the same basic chemical structure, but each has a specific "side-chain" that determines the amino acid type. The three BCAAs have a side-chain that forms in a branched-like formation as opposed to the ring-like formation of other AAs. The importance of BCAAs in humans is underscored by the fact that BCAAs make up one-third of all AAs present in muscle protein. Given that muscle accounts for about 40% of body mass in humans, this is an enormous pool of BCAAs in the body.

During prolonged exercise, BCAAs can be utilised within the mitochondria of skeletal muscles to produce energy, but this is not a major source of energy production. However, in situations where dietary carbohydrate is low, energy intake is restricted, or if exercising in the fasting state, BCAAs can make a more meaningful contribution to energy production. It is worth noting that the majority of BCAAs in this situation come from the breakdown of muscle tissue, so this is generally a situation that should be avoided as an athlete. Other amino acids are mainly metabolized within the liver and can be used to produce sugar (i.e. glucose, by a process known as gluconeogenesis) that can also be used for energy production. On the other hand, the growth of muscle in response to exercise is determined in part by the intake and timing of protein in relation to training, and especially the dietary content of the BCAA, leucine. These metabolic processes are part of the reason that BCAAs and protein needs in general are higher in athletes compared to non-athletes.

What does the research say about BCAAs?

BCAAs have become one of the most widely researched nutrient groups in the past 20 years. Here are just a few of the published effects of BCAAs supplementation.

(i) Stimulation of muscle protein synthesis

BCAA ingestion acutely stimulates skeletal muscle protein synthesis (a measure of muscle growth) 2, 3, 4, 5, 6, and when consumed either before, during or after resistance exercise results in a greater increase in protein synthesis compared to placebo or carbohydrate alone 7, 8, 9, 10. Although most of these effects appear to be exerted by leucine, it is premature at present to rule out a role for valine and isoleucine. Combining BCAAs with sugars (e.g. glucose, maltodextrin, Vitargo) can result in an even greater increase in protein synthesis in the immediate recovery period 8, 9, 10. Interestingly, leucine is now seen as a key nutrient to be used in elderly populations for the prevention of muscle wasting 11.

(ii) Promotion of fat loss and preservation of muscle mass during weight loss

It is well established that a diet higher in protein can allow for preservation of muscle mass on a weight loss diet 12. In addition, supplementing with BCAA during periods of energy restriction, weight loss and in physically demanding situations (e.g. climbing at altitude) has been shown to result in preservation of lean tissue mass, and greater amounts of fat loss 13, 14, 15. In wrestlers, this resulted in maintenance of exercise performance compared to a non-supplemented, low protein group 13.

(iii) Reduction in muscle soreness and aiding recovery

BCAA ingestion either daily (~10-20 g/day), acutely (~ 9 g) before, during and after training, or at regular intervals during recovery have all been shown to reduce muscle soreness (known as DOMS or delayed onset muscle soreness) and markers of muscle damage after intense training sessions, for both gym/resistance- and endurance-based training 16, 17, 18, 19.

(iv) Protection of immune function

BCAA ingestion daily (~12 g/day) can prevent the temporary decline in immune function that is often observed during recovery from exercise, and thereby reduce the risk of illness in athletes 20.

What does this mean in practice?

Weight loss diets: Consuming around 10 g of either EAAs or BCAAs at regular intervals e.g. between main meals during a calorie deficit (or if fasting) should help to offset the loss of muscle tissue, while also promoting fat loss.

Endurance- or field-type training: Consuming ~10 g of BCAA before, during or after exercise, or ~20 g daily, should reduce the effects of muscle soreness and improve immune function during heavy training periods

Gym-based training: consuming a blend of AAs and carbohydrate around your gym session will promote greater gains in muscle mass, reduce muscle soreness and speed recovery between sessions. For more information of the specifics of the timing and quantities of BCAA, protein and carbohydrate ingestion around your training session, please see our article on "Nutrient timing". However, in terms of dosage and the maximum response using muscle protein synthesis as a marker, the upper limit in terms of a single dose is either ~10-12 g of EAA, 6-8 g of BCAA, or ~4 g of leucine, but may be repeated every 2-4 hours.

Find amino acids at ROS

Of the various powdered protein sources (e.g. whey, casein, egg white, hemp), whey protein has the highest proportion of BCAAs (~25%) on per gram dried basis, followed closely by casein and egg protein powders. If your goal involves high intakes of BCAAs, a variety of ROS formulations based on these protein powders provide BCAAs in ample amounts such as Meta Muscle®, Target Whey Protein®, Calcium Caseinate, Blue Label Whey®, FEMME MEAL®, FEMME SHAPE® RecoverAce Strength® and RecoverAce Endurance®. Plant-protein powders such as hemp, rice and pea protein contain slightly lower concentrations of BCAAs, but have the disadvantage of not providing all EAAs required by the body. However, if you are interested in isolated amino acids for example, if you are looking for high BCAA intakes in the absence of a large caloric intake we have the products for you.

1. ISO EAA® :

ISO EAA® is a blend of the EAAs available in convenient 1 g tablets. In addition, BCAAs make up 2/3 of the total amino acid profile in these tablets. These are suitable for consumption as part of a daily diet e.g. vegetarians who may be at risk for deficiencies in EAAs, or in athletes who wish to consume a source of amino acids prior to or immediately after an intense work-out.

1. ISO BCAA® :

ISO BCAA® is a blend of BCAAs available in three forms: (i) in unflavoured, micro-ionised quality powder form with the classic 2:1:1 ratio of leucine: valine: isoleucine; (ii) in 1 g tablets with the same ratio but with the added benefit of ethyl ester derivatives and Bioperine® to promote their absorption into the blood; (iii) in flavoured powdered form with the 2:1:1 ratio, combined with the 5 g per serving of the anti-catabolic amino acid glutamine, and added ornithine and arginine to promote growth hormone release during exercise to further stimulate an anabolic effect. By their nature, isolated BCAAs have a distinctive, somewhat disagreeable, taste but at ROS we have invested time and effort in supplying what we believe to be the best tasting BCAA supplement on the market. Try it now! All three of our BCAA products are perfect for supplementing before, during and after a field or gym workout in order to limit muscle protein breakdown, and promote an anabolic environment in the aftermath of training in order to help you recover and adapt faster.


As part of our ROSFUEL® range, all isolated amino acid products are certified as free from prohibited substances from the WADA list as verified by independent testing by Informed Sport.

Further reading

  • Tipton KD, Wolfe RR (2004) Protein and amino acids for athletes. J Sports Sci. 22 (1), 65-79.
  • Glynn EL, Fry CS, Drummond MJ, Timmerman KL, Dhanani S, Volpi E, Rasmussen BB (2010) Excess leucine intake enhances muscle anabolic signaling but not net protein anabolism in young men and women. J Nutr. 140 (11), 1970-1976.
  • Cuthbertson D, Smith K, Babraj J, Leese G, Waddell T, Atherton P, Wackerhage H, Taylor PM, Rennie MJ (2005) Anabolic signaling deficits underlie amino acid resistance of wasting, aging muscle. FASEB J. 19 (3), 422-424.
  • Biolo G, Tipton KD, Klein S, Wolfe RR (1997) An abundant supply of amino acids enhances the metabolic effect of exercise on muscle protein. Am J Physiol. 273 (1 Pt 1), E122-E129.
  • Tipton KD, Gurkin BE, Matin S, Wolfe RR (1999) Nonessential amino acids are not necessary to stimulate net muscle protein synthesis in healthy volunteers. J Nutr Biochem. 10 (2), 89-95.
  • Bohe J, Low A, Wolfe RR, Rennie MJ (2003) Human muscle protein synthesis is modulated by extracellular, not intramuscular amino acid availability: a dose-response study. J Physiol. 552 (Pt 1), 315-324.
  • Miller SL, Tipton KD, Chinkes DL, Wolf SE, Wolfe RR (2003) Independent and combined effects of amino acids and glucose after resistance exercise. Med Sci Sports Exerc. 35 (3), 449-455.
  • Tipton KD, Rasmussen BB, Miller SL, Wolf SE, Owens-Stovall SK, Petrini BE, Wolfe RR (2001) Timing of amino acid-carbohydrate ingestion alters anabolic response of muscle to resistance exercise. Am J Physiol Endocrinol Metab. 281 (2), E197-E206.
  • Borsheim E, Cree MG, Tipton KD, Elliott TA, Aarsland A, Wolfe RR (2004) Effect of carbohydrate intake on net muscle protein synthesis during recovery from resistance exercise. J Appl Physiol. 96 (2), 674-678.
  • Borsheim E, Aarsland A, Wolfe RR (2004) Effect of an amino acid, protein, and carbohydrate mixture on net muscle protein balance after resistance exercise. Int J Sport Nutr Exerc Metab. 14 (3), 255-271.
  • Leenders M, van Loon LJ (2011) Leucine as a pharmaconutrient to prevent and treat sarcopenia and type 2 diabetes. Nutr Rev. 69 (11), 675-689.
  • Evans EM, Mojtahedi MC, Thorpe MP, Valentine RJ, Kris-Etherton PM, Layman DK (2012) Effects of protein intake and gender on body composition changes: a randomized clinical weight loss trial. Nutr Metab (Lond). 9 (1), 55.
  • Mourier A, Bigard AX, de KE, Roger B, Legrand H, Guezennec CY (1997) Combined effects of caloric restriction and branched-chain amino acid supplementation on body composition and exercise performance in elite wrestlers. Int J Sports Med. 18 (1), 47-55.
  • Donato J, Jr., Pedrosa RG, Cruzat VF, Pires IS, Tirapegui J (2006) Effects of leucine supplementation on the body composition and protein status of rats submitted to food restriction. Nutrition. 22 (5), 520-527.
  • Schena F, Guerrini F, Tregnaghi P, Kayser B (1992) Branched-chain amino acid supplementation during trekking at high altitude. The effects on loss of body mass, body composition, and muscle power. Eur J Appl Physiol Occup Physiol. 65 (5), 394-398.
  • Coombes JS, McNaughton LR (2000) Effects of branched-chain amino acid supplementation on serum creatine kinase and lactate dehydrogenase after prolonged exercise. J Sports Med Phys Fitness. 40 (3), 240-246.
  • Shimomura Y, Inaguma A, Watanabe S, Yamamoto Y, Muramatsu Y, Bajotto G, Sato J, Shimomura N, Kobayashi H, Mawatari K (2010) Branched-chain amino acid supplementation before squat exercise and delayed-onset muscle soreness. Int J Sport Nutr Exerc Metab. 20 (3), 236-244.
  • Jackman SR, Witard OC, Jeukendrup AE, Tipton KD (2010) Branched-chain amino acid ingestion can ameliorate soreness from eccentric exercise. Med Sci Sports Exerc. 42 (5), 962-970.
  • Howatson G, Hoad M, Goodall S, Tallent J, Bell PG, French DN (2012) Exercise-induced muscle damage is reduced in resistance-trained males by branched chain amino acids: a randomized, double-blind, placebo controlled study. J Int Soc Sports Nutr. 9 (1), 20.
  • Bassit RA, Sawada LA, Bacurau RF, Navarro F, Costa Rosa LF (2000) The effect of BCAA supplementation upon the immune response of triathletes. Med Sci Sports Exerc. 32 (7), 1214-1219.