Branched-Chain Amino Acids

Last Updated: February 1 2023

Branched-chain amino acids (BCAAs) are three essential amino acids that are frequently supplemented because of their role in muscle growth and development. These amino acids are naturally found in dietary protein sources. Studies show that supplementation of BCAAs alone does not increase muscle growth, as all essential amino acids must be present for muscle protein synthesis to occur.

Branched-Chain Amino Acids is most often used for

What are branched-chain amino acids?

BCAAs refer to three essential amino acids: leucine, isoleucine, and valine. They are distinct from other essential amino acids as they possess a branched side chain and play a large role in the regulation of muscle mass. They are present in high amounts in muscle tissue in comparison to other essential amino acids.[143] BCAAs cannot be synthesized in the body, so they are important to ingest daily. Daily protein sources, such as eggs and meat, typically provide an adequate amount.[144]

What are branched-chain amino acids’ main benefits?

The main benefit of BCAAs are their ability to enhance muscle growth and alleviate muscle fatigue. Studies found that supplementing with BCAAs alone does not provide an optimal muscle protein synthesis response, as all essential amino acids are required for muscle protein synthesis.[145][146] There seems to be a role for BCAA supplementation in increasing muscle protein synthesis if they are taken along with a meal that has an adequate amount of essential amino acids.[146] However, there is no evidence that BCAA supplementation enhances muscle strength or hypertrophy when adequate protein requirements are met.[144] BCAA supplementation for fatigue may be beneficial, based on a meta-analysis of BCAA effects on markers of muscle damage. The results found that BCAA supplementation reduced muscle damage and muscle soreness after exercise, but may not speed up the recovery of muscle performance.[147]

What are branched-chain amino acids’ main drawbacks?

There is a growing interest in understanding the correlation between the amount of BCAAs present within the body and insulin resistance. In insulin resistant states, such as in people with obesity, there appear to be higher circulating levels of BCAAs.[148] However, serum BCAAs seem to be more of a biomarker of insulin resistance, and their potentially causative role is not well understood and requires further research.

How do branched-chain amino acids work?

Amino acids are the building blocks of proteins, and adequate amounts of all essential amino acids are required for adequate protein synthesis. BCAAs alone do not promote muscle protein synthesis.[145]

What else is Branched-Chain Amino Acids known as?
Note that Branched-Chain Amino Acids is also known as:
  • BCAAs
  • BCAA
Branched-Chain Amino Acids should not be confused with:
Dosage information

The three BCAAs are leucine, isoleucine, and valine. They’re considered the most anabolic of the nine essential amino acids and have therefore been marketed as a sports supplement. However, it's possible that only leucine is especially anabolic, and that leucine taken alone is actually more anabolic than leucine taken with isoleucine and valine, due to competition for both absorption in the gut and entry into muscle tissue.

The standard leucine dosage is 2–10 grams. The standard dosage for isoleucine is 48–72 milligrams per kilogram of bodyweight, assuming a non-obese person. Further research is needed to determine valine’s optimal dosage and the reason for supplementation.

A combination dose is 20 grams of combined BCAAs, with a balanced ratio of leucine and isoleucine.

Supplementation with BCAAs is not necessary if enough BCAAs are provided through the diet.

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7.^Yoshiji H, Noguchi R, Ikenaka Y, Kaji K, Aihara Y, Douhara A, Yamao J, Toyohara M, Mitoro A, Sawai M, Yoshida M, Morioka C, Fujimoto M, Uemura M, Fukui HCombination of branched-chain amino acid and angiotensin-converting enzyme inhibitor improves liver fibrosis progression in patients with cirrhosisMol Med Report.(2012 Feb)
8.^Reynolds B, Laynes R, Ogmundsdóttir MH, Boyd CA, Goberdhan DCAmino acid transporters and nutrient-sensing mechanisms: new targets for treating insulin-linked disordersBiochem Soc Trans.(2007 Nov)
9.^Boado RJ, Li JY, Nagaya M, Zhang C, Pardridge WMSelective expression of the large neutral amino acid transporter at the blood-brain barrierProc Natl Acad Sci U S A.(1999 Oct 12)
10.^Pardridge WM, Choi TBNeutral amino acid transport at the human blood-brain barrierFed Proc.(1986 Jun)
12.^Harris RA, Zhang B, Goodwin GW, Kuntz MJ, Shimomura Y, Rougraff P, Dexter P, Zhao Y, Gibson R, Crabb DWRegulation of the branched-chain alpha-ketoacid dehydrogenase and elucidation of a molecular basis for maple syrup urine diseaseAdv Enzyme Regul.(1990)
14.^Kobayashi R, Shimomura Y, Murakami T, Nakai N, Otsuka M, Arakawa N, Shimizu K, Harris RAHepatic branched-chain alpha-keto acid dehydrogenase complex in female rats: activation by exercise and starvationJ Nutr Sci Vitaminol (Tokyo).(1999 Jun)
15.^Shimomura Y, Murakami T, Nakai N, Nagasaki M, Obayashi M, Li Z, Xu M, Sato Y, Kato T, Shimomura N, Fujitsuka N, Tanaka K, Sato MSuppression of glycogen consumption during acute exercise by dietary branched-chain amino acids in ratsJ Nutr Sci Vitaminol (Tokyo).(2000 Apr)
16.^Howarth KR, Burgomaster KA, Phillips SM, Gibala MJExercise training increases branched-chain oxoacid dehydrogenase kinase content in human skeletal muscleAm J Physiol Regul Integr Comp Physiol.(2007 Sep)
17.^Harper AE, Miller RH, Block KPBranched-chain amino acid metabolismAnnu Rev Nutr.(1984)
20.^Shimomura Y, Nanaumi N, Suzuki M, Popov KM, Harris RAPurification and partial characterization of branched-chain alpha-ketoacid dehydrogenase kinase from rat liver and rat heartArch Biochem Biophys.(1990 Dec)
22.^Suryawan A, Hawes JW, Harris RA, Shimomura Y, Jenkins AE, Hutson SMA molecular model of human branched-chain amino acid metabolismAm J Clin Nutr.(1998 Jul)
23.^Xu M, Nagasaki M, Obayashi M, Sato Y, Tamura T, Shimomura YMechanism of activation of branched-chain alpha-keto acid dehydrogenase complex by exerciseBiochem Biophys Res Commun.(2001 Sep 28)
24.^Paxton R, Harris RARegulation of branched-chain alpha-ketoacid dehydrogenase kinaseArch Biochem Biophys.(1984 May 15)
25.^Kobayashi R, Murakami T, Obayashi M, Nakai N, Jaskiewicz J, Fujiwara Y, Shimomura Y, Harris RAClofibric acid stimulates branched-chain amino acid catabolism by three mechanismsArch Biochem Biophys.(2002 Nov 15)
26.^Teräväinen H, Larsen A, Hillbom MClofibrate-induced myopathy in the ratActa Neuropathol.(1977 Aug 16)
28.^Shiraki M, Shimomura Y, Miwa Y, Fukushima H, Murakami T, Tamura T, Tamura N, Moriwaki HActivation of hepatic branched-chain alpha-keto acid dehydrogenase complex by tumor necrosis factor-alpha in ratsBiochem Biophys Res Commun.(2005 Mar 25)
29.^Shimomura Y, Fujii H, Suzuki M, Fujitsuka N, Naoi M, Sugiyama S, Harris RABranched-chain 2-oxo acid dehydrogenase complex activation by tetanic contractions in rat skeletal muscleBiochim Biophys Acta.(1993 Jul 11)
30.^Wagenmakers AJ, Brookes JH, Coakley JH, Reilly T, Edwards RHExercise-induced activation of the branched-chain 2-oxo acid dehydrogenase in human muscleEur J Appl Physiol Occup Physiol.(1989)
31.^Ament W, Verkerke GJExercise and fatigueSports Med.(2009)
32.^Davis JM, Alderson NL, Welsh RSSerotonin and central nervous system fatigue: nutritional considerationsAm J Clin Nutr.(2000 Aug)
34.^Blomstrand EAmino acids and central fatigueAmino Acids.(2001)
37.^Fernstrom JD, Faller DVNeutral amino acids in the brain: changes in response to food ingestionJ Neurochem.(1978 Jun)
39.^Blomstrand E, Møller K, Secher NH, Nybo LEffect of carbohydrate ingestion on brain exchange of amino acids during sustained exercise in human subjectsActa Physiol Scand.(2005 Nov)
40.^Nybo L, Nielsen B, Blomstrand E, Moller K, Secher NNeurohumoral responses during prolonged exercise in humansJ Appl Physiol.(2003 Sep)
41.^Meeusen R, Thorré K, Chaouloff F, Sarre S, De Meirleir K, Ebinger G, Michotte YEffects of tryptophan and/or acute running on extracellular 5-HT and 5-HIAA levels in the hippocampus of food-deprived ratsBrain Res.(1996 Nov 18)
42.^Falavigna G, Alves de Araújo J Jr, Rogero MM, Pires IS, Pedrosa RG, Martins E Jr, Alves de Castro I, Tirapegui JEffects of diets supplemented with branched-chain amino acids on the performance and fatigue mechanisms of rats submitted to prolonged physical exerciseNutrients.(2012 Nov 16)
43.^Gomez-Merino D, Béquet F, Berthelot M, Riverain S, Chennaoui M, Guezennec CYEvidence that the branched-chain amino acid L-valine prevents exercise-induced release of 5-HT in rat hippocampusInt J Sports Med.(2001 Jul)
47.^Valenti M, Pontieri FE, Conti F, Altobelli E, Manzoni T, Frati LAmyotrophic lateral sclerosis and sports: a case-control studyEur J Neurol.(2005 Mar)
48.^Carunchio I, Curcio L, Pieri M, Pica F, Caioli S, Viscomi MT, Molinari M, Canu N, Bernardi G, Zona CIncreased levels of p70S6 phosphorylation in the G93A mouse model of Amyotrophic Lateral Sclerosis and in valine-exposed cortical neurons in cultureExp Neurol.(2010 Nov)
50.^Zanette G, Tamburin S, Manganotti P, Refatti N, Forgione A, Rizzuto NChanges in motor cortex inhibition over time in patients with amyotrophic lateral sclerosisJ Neurol.(2002 Dec)
52.^van Zundert B, Peuscher MH, Hynynen M, Chen A, Neve RL, Brown RH Jr, Constantine-Paton M, Bellingham MCNeonatal neuronal circuitry shows hyperexcitable disturbance in a mouse model of the adult-onset neurodegenerative disease amyotrophic lateral sclerosisJ Neurosci.(2008 Oct 22)
54.^Uberall F, Hellbert K, Kampfer S, Maly K, Villunger A, Spitaler M, Mwanjewe J, Baier-Bitterlich G, Baier G, Grunicke HHEvidence that atypical protein kinase C-lambda and atypical protein kinase C-zeta participate in Ras-mediated reorganization of the F-actin cytoskeletonJ Cell Biol.(1999 Feb 8)
55.^Nishitani S, Matsumura T, Fujitani S, Sonaka I, Miura Y, Yagasaki KLeucine promotes glucose uptake in skeletal muscles of ratsBiochem Biophys Res Commun.(2002 Dec 20)
57.^Tessari P, Inchiostro S, Biolo G, Duner E, Nosadini R, Tiengo A, Crepaldi GHyperaminoacidaemia reduces insulin-mediated glucose disposal in healthy manDiabetologia.(1985 Nov)
61.^O'Neill HMAMPK and Exercise: Glucose Uptake and Insulin SensitivityDiabetes Metab J.(2013 Feb)
64.^Haruta T, Uno T, Kawahara J, Takano A, Egawa K, Sharma PM, Olefsky JM, Kobayashi MA rapamycin-sensitive pathway down-regulates insulin signaling via phosphorylation and proteasomal degradation of insulin receptor substrate-1Mol Endocrinol.(2000 Jun)
65.^Newgard CB, An J, Bain JR, Muehlbauer MJ, Stevens RD, Lien LF, Haqq AM, Shah SH, Arlotto M, Slentz CA, Rochon J, Gallup D, Ilkayeva O, Wenner BR, Yancy WS Jr, Eisenson H, Musante G, Surwit RS, Millington DS, Butler MD, Svetkey LPA branched-chain amino acid-related metabolic signature that differentiates obese and lean humans and contributes to insulin resistanceCell Metab.(2009 Apr)
66.^Wang TJ, Larson MG, Vasan RS, Cheng S, Rhee EP, McCabe E, Lewis GD, Fox CS, Jacques PF, Fernandez C, O'Donnell CJ, Carr SA, Mootha VK, Florez JC, Souza A, Melander O, Clish CB, Gerszten REMetabolite profiles and the risk of developing diabetesNat Med.(2011 Apr)
67.^Doi M, Yamaoka I, Fukunaga T, Nakayama MIsoleucine, a potent plasma glucose-lowering amino acid, stimulates glucose uptake in C2C12 myotubesBiochem Biophys Res Commun.(2003 Dec 26)
71.^Armstrong JL, Bonavaud SM, Toole BJ, Yeaman SJRegulation of glycogen synthesis by amino acids in cultured human muscle cellsJ Biol Chem.(2001 Jan 12)
72.^Letto J, Brosnan ME, Brosnan JTValine metabolism. Gluconeogenesis from 3-hydroxyisobutyrateBiochem J.(1986 Dec 15)
73.^van Hall G, MacLean DA, Saltin B, Wagenmakers AJMechanisms of activation of muscle branched-chain alpha-keto acid dehydrogenase during exercise in manJ Physiol.(1996 Aug 1)
74.^Gibala MJ, Young ME, Taegtmeyer HAnaplerosis of the citric acid cycle: role in energy metabolism of heart and skeletal muscleActa Physiol Scand.(2000 Apr)
75.^Gualano AB, Bozza T, Lopes De Campos P, Roschel H, Dos Santos Costa A, Luiz Marquezi M, Benatti F, Herbert Lancha Junior ABranched-chain amino acids supplementation enhances exercise capacity and lipid oxidation during endurance exercise after muscle glycogen depletionJ Sports Med Phys Fitness.(2011 Mar)
76.^Blomstrand E, Hassmén P, Ek S, Ekblom B, Newsholme EAInfluence of ingesting a solution of branched-chain amino acids on perceived exertion during exerciseActa Physiol Scand.(1997 Jan)
77.^Marchesini G, Bianchi G, Merli M, Amodio P, Panella C, Loguercio C, Rossi Fanelli F, Abbiati R; Italian BCAA Study GroupNutritional supplementation with branched-chain amino acids in advanced cirrhosis: a double-blind, randomized trialGastroenterology.(2003 Jun)
78.^Kawamura-Yasui N, Kaito M, Nakagawa N, Fujita N, Ikoma J, Gabazza EC, Watanabe S, Adachi YEvaluating response to nutritional therapy using the branched-chain amino acid/tyrosine ratio in patients with chronic liver diseaseJ Clin Lab Anal.(1999)
79.^Nishitani S, Takehana K, Fujitani S, Sonaka IBranched-chain amino acids improve glucose metabolism in rats with liver cirrhosisAm J Physiol Gastrointest Liver Physiol.(2005 Jun)
80.^Takeshita Y, Takamura T, Kita Y, Ando H, Ueda T, Kato K, Misu H, Sunagozaka H, Sakai Y, Yamashita T, Mizukoshi E, Honda M, Kaneko SBeneficial effect of branched-chain amino acid supplementation on glycemic control in chronic hepatitis C patients with insulin resistance: implications for type 2 diabetesMetabolism.(2012 Oct)
81.^Felig P, Marliss E, Cahill GF JrPlasma amino acid levels and insulin secretion in obesityN Engl J Med.(1969 Oct 9)
83.^Shah SH, Crosslin DR, Haynes CS, Nelson S, Turer CB, Stevens RD, Muehlbauer MJ, Wenner BR, Bain JR, Laferrère B, Gorroochurn P, Teixeira J, Brantley PJ, Stevens VJ, Hollis JF, Appel LJ, Lien LF, Batch B, Newgard CB, Svetkey LPBranched-chain amino acid levels are associated with improvement in insulin resistance with weight lossDiabetologia.(2012 Feb)
84.^Tai ES, Tan ML, Stevens RD, Low YL, Muehlbauer MJ, Goh DL, Ilkayeva OR, Wenner BR, Bain JR, Lee JJ, Lim SC, Khoo CM, Shah SH, Newgard CBInsulin resistance is associated with a metabolic profile of altered protein metabolism in Chinese and Asian-Indian menDiabetologia.(2010 Apr)
85.^She P, Reid TM, Bronson SK, Vary TC, Hajnal A, Lynch CJ, Hutson SMDisruption of BCATm in mice leads to increased energy expenditure associated with the activation of a futile protein turnover cycleCell Metab.(2007 Sep)
86.^Pietiläinen KH, Naukkarinen J, Rissanen A, Saharinen J, Ellonen P, Keränen H, Suomalainen A, Götz A, Suortti T, Yki-Järvinen H, Oresic M, Kaprio J, Peltonen LGlobal transcript profiles of fat in monozygotic twins discordant for BMI: pathways behind acquired obesityPLoS Med.(2008 Mar 11)
88.^Lu J, Xie G, Jia W, Jia WInsulin resistance and the metabolism of branched-chain amino acidsFront Med.(2013 Mar)
89.^Xiao F, Huang Z, Li H, Yu J, Wang C, Chen S, Meng Q, Cheng Y, Gao X, Li J, Liu Y, Guo FLeucine deprivation increases hepatic insulin sensitivity via GCN2/mTOR/S6K1 and AMPK pathwaysDiabetes.(2011 Mar)
91.^Anthony JC, Yoshizawa F, Anthony TG, Vary TC, Jefferson LS, Kimball SRLeucine stimulates translation initiation in skeletal muscle of postabsorptive rats via a rapamycin-sensitive pathwayJ Nutr.(2000 Oct)
92.^Drummond MJ, Fry CS, Glynn EL, Dreyer HC, Dhanani S, Timmerman KL, Volpi E, Rasmussen BBRapamycin administration in humans blocks the contraction-induced increase in skeletal muscle protein synthesisJ Physiol.(2009 Apr 1)
94.^Blomstrand E, Eliasson J, Karlsson HK, Köhnke RBranched-chain amino acids activate key enzymes in protein synthesis after physical exerciseJ Nutr.(2006 Jan)
95.^Wang X, Proud CGThe mTOR pathway in the control of protein synthesisPhysiology (Bethesda).(2006 Oct)
96.^Proud CGmTOR-mediated regulation of translation factors by amino acidsBiochem Biophys Res Commun.(2004 Jan 9)
102.^Vander Haar E, Lee SI, Bandhakavi S, Griffin TJ, Kim DHInsulin signalling to mTOR mediated by the Akt/PKB substrate PRAS40Nat Cell Biol.(2007 Mar)
103.^Elmadhun NY, Lassaletta AD, Chu LM, Sellke FWMetformin alters the insulin signaling pathway in ischemic cardiac tissue in a swine model of metabolic syndromeJ Thorac Cardiovasc Surg.(2013 Jan)
106.^Alvestrand A, Hagenfeldt L, Merli M, Oureshi A, Eriksson LSInfluence of leucine infusion on intracellular amino acids in humansEur J Clin Invest.(1990 Jun)
108.^Greiwe JS, Kwon G, McDaniel ML, Semenkovich CFLeucine and insulin activate p70 S6 kinase through different pathways in human skeletal muscleAm J Physiol Endocrinol Metab.(2001 Sep)
110.^Inoki K, Li Y, Zhu T, Wu J, Guan KLTSC2 is phosphorylated and inhibited by Akt and suppresses mTOR signallingNat Cell Biol.(2002 Sep)
113.^Browne GJ, Proud CGRegulation of peptide-chain elongation in mammalian cellsEur J Biochem.(2002 Nov)
115.^Bodine SC, Latres E, Baumhueter S, Lai VK, Nunez L, Clarke BA, Poueymirou WT, Panaro FJ, Na E, Dharmarajan K, Pan ZQ, Valenzuela DM, DeChiara TM, Stitt TN, Yancopoulos GD, Glass DJIdentification of ubiquitin ligases required for skeletal muscle atrophyScience.(2001 Nov 23)
116.^Sandri M, Sandri C, Gilbert A, Skurk C, Calabria E, Picard A, Walsh K, Schiaffino S, Lecker SH, Goldberg ALFoxo transcription factors induce the atrophy-related ubiquitin ligase atrogin-1 and cause skeletal muscle atrophyCell.(2004 Apr 30)
117.^Stitt TN, Drujan D, Clarke BA, Panaro F, Timofeyva Y, Kline WO, Gonzalez M, Yancopoulos GD, Glass DJThe IGF-1/PI3K/Akt pathway prevents expression of muscle atrophy-induced ubiquitin ligases by inhibiting FOXO transcription factorsMol Cell.(2004 May 7)
119.^Newsholme P, Brennan L, Rubi B, Maechler PNew insights into amino acid metabolism, beta-cell function and diabetesClin Sci (Lond).(2005 Mar)
121.^Lynch CJ, Patson BJ, Anthony J, Vaval A, Jefferson LS, Vary TCLeucine is a direct-acting nutrient signal that regulates protein synthesis in adipose tissueAm J Physiol Endocrinol Metab.(2002 Sep)
122.^Lynch CJ, Hutson SM, Patson BJ, Vaval A, Vary TCTissue-specific effects of chronic dietary leucine and norleucine supplementation on protein synthesis in ratsAm J Physiol Endocrinol Metab.(2002 Oct)
123.^Lynch CJ, Fox HL, Vary TC, Jefferson LS, Kimball SRRegulation of amino acid-sensitive TOR signaling by leucine analogues in adipocytesJ Cell Biochem.(2000 Mar)
124.^Jin G, Kataoka Y, Tanaka M, Mizuma H, Nozaki S, Tahara T, Mizuno K, Yamato M, Watanabe YChanges in plasma and tissue amino acid levels in an animal model of complex fatigueNutrition.(2009 May)
125.^Shimomura Y, Inaguma A, Watanabe S, Yamamoto Y, Muramatsu Y, Bajotto G, Sato J, Shimomura N, Kobayashi H, Mawatari KBranched-chain amino acid supplementation before squat exercise and delayed-onset muscle sorenessInt J Sport Nutr Exerc Metab.(2010 Jun)
126.^Ispoglou T, King RF, Polman RC, Zanker CDaily L-leucine supplementation in novice trainees during a 12-week weight training programInt J Sports Physiol Perform.(2011 Mar)
128.^Portier H, Chatard JC, Filaire E, Jaunet-Devienne MF, Robert A, Guezennec CYEffects of branched-chain amino acids supplementation on physiological and psychological performance during an offshore sailing raceEur J Appl Physiol.(2008 Nov)
129.^Bigard AX, Lavier P, Ullmann L, Legrand H, Douce P, Guezennec CYBranched-chain amino acid supplementation during repeated prolonged skiing exercises at altitudeInt J Sport Nutr.(1996 Sep)
130.^Shimizu M, Miyagawa K, Iwashita S, Noda T, Hamada K, Genno H, Nose HEnergy expenditure during 2-day trail walking in the mountains (2,857 m) and the effects of amino acid supplementation in older men and womenEur J Appl Physiol.(2012 Mar)
135.^Shimomura Y, Kobayashi H, Mawatari K, Akita K, Inaguma A, Watanabe S, Bajotto G, Sato JEffects of squat exercise and branched-chain amino acid supplementation on plasma free amino acid concentrations in young womenJ Nutr Sci Vitaminol (Tokyo).(2009 Jun)
140.^Elango R, Chapman K, Rafii M, Ball RO, Pencharz PBDetermination of the tolerable upper intake level of leucine in acute dietary studies in young menAm J Clin Nutr.(2012 Oct)