BCAAs (branched-chain amino acids)

What the evidence says

Each claim is rated on its own evidence. Ratings follow the scale on our methodology page.

• Reduces muscle soreness and markers of muscle damage after hard exercise Evidence rating: Limited

  People who lift weights or run take it hoping to feel less sore and bounce back faster after a hard workout.

  Two reviews of small trials found less soreness and lower muscle-damage markers at some time points, but disagree on when, and a third concluded the effect seems poor.

  This claim is about muscle soreness that comes on after hard exercise, and about blood markers of muscle damage such as creatine kinase (CK). A 2024 review pooled 18 small randomized trials of BCAAs on their own against a placebo, in healthy active people, mostly men. Soreness was lower with BCAAs from one to four days after exercise, but not straight after it. CK was lower straight after exercise and at three days, but not at one, two or four days. Another marker, lactate dehydrogenase, did not change.

  The 2024 review found signs of publication bias for soreness at some time points. Its authors say the results may be influenced by study design, blinding, training status and sex: at some time points, effects were larger in single-blinded than double-blinded trials, and in trials comparing separate groups than in crossover trials.

  A 2021 review of nine trials, limited to trained men doing resistance exercise, found lower CK within the first day and at one and two days. It found less soreness only within the first day; at one and two days the difference was not significant. Its authors say the soreness result should not be considered conclusive, because one trial with no effect weighed on it. Eight of its nine trials are also among the 18 in the 2024 review, so the two reviews largely analyze the same trials rather than confirming each other. They disagree about when soreness eases.

  A 2017 review of 11 trials did not pool them. It found as many trials with no effect as with a benefit, and the better-quality trials mostly found no significant effect. It concluded that the efficacy of BCAAs for reducing muscle damage from high-intensity exercise “seems to be poor”, with a possible benefit under specific conditions, such as several days of supplements before the exercise. A 2022 review of studies in athletes reported that BCAAs mostly eased soreness after resistance exercise, with inconsistent results in endurance sports.

  ODS, NIH’s Office of Dietary Supplements, says studies have not consistently shown that BCAAs aid recovery from exercise. In 2010 EFSA, the EU food safety agency, concluded that faster recovery from muscle fatigue, meaning regaining strength after exercise, had not been established for BCAAs. None of the reviews graded its evidence. This page rates the claim limited: two reviews report some benefit, but at different times, a third review concluded the effect seems poor, and ODS and EFSA did not find faster recovery shown.

  Sources: Source [1]Source [2]Source [3]Source [4]Source [5]Source [6]

• Increases muscle protein synthesis and muscle growth beyond what protein in general provides Evidence rating: Insufficient

  People who lift weights take it hoping to build more muscle than training and a normal diet would.

  EFSA found in 2010 that BCAAs had not been shown to build or keep muscle beyond protein’s known role, and ODS calls the evidence on muscle protein-building inconsistent.

  This claim compares BCAAs with protein in general, the way EFSA, the European Union’s food safety agency, framed it in 2010. The claims sent to EFSA said BCAAs increase protein synthesis and reduce protein breakdown after exercise. EFSA assessed them as claims about growing or keeping muscle, and noted that it had already accepted a claim that protein in general does this.

  EFSA found no references from which conclusions could be drawn. Two small studies at high altitude estimated muscle size, but the BCAA groups also got more protein, and the studies did not compare the groups directly. EFSA concluded that an effect of BCAAs on growing or keeping muscle, over and above the well-established role of protein, had not been established.

  ODS, NIH’s Office of Dietary Supplements, gives both sides. It says several short-term studies, lasting about three to six weeks, suggest BCAAs might enhance gains in muscle mass and strength during training. But it says that, overall, studies give inconsistent evidence that BCAAs stimulate muscle protein synthesis beyond what enough high-quality protein does. A 2022 review of studies in athletes found negligible effects on lean and fat mass in the few studies that measured them.

  This page found no review of BCAAs for muscle in older adults that it could read in full. It rates the claim insufficient: the cited evidence is too limited to show whether BCAAs add anything to protein for building muscle.

  Sources: Source [1]Source [2]Source [3]

• Improves exercise performance in athletes and people who train regularly Evidence rating: Evidence against

  Athletes take it hoping to perform better and tire less in training and competition.

  A 2022 review of studies in athletes concluded that BCAAs do not appear to improve performance, and ODS and EFSA found no consistent or established benefit.

  A 2022 review gathered 24 studies of BCAAs taken by mouth in athletes and people who train regularly, two of which used a similar group of people. They included cyclists, runners, people doing resistance training, and volleyball and soccer players. The review left out products that combined BCAAs with other substances. It concluded that BCAAs had minimal effects on performance and do not appear to have a significant impact on it.

  Individual studies varied. In one, people on a reduced-calorie diet who did resistance training for eight weeks gained strength with BCAAs, while upper-body strength barely changed with carbohydrate. In another, cyclists who took BCAAs for ten weeks reached a higher peak power, but their diet was not controlled. Most studies did not report how much protein participants ate, and the reviewers say the benefits of BCAAs should be read with caution.

  Some people take BCAAs to tire less. ODS, NIH’s Office of Dietary Supplements, says BCAAs might delay feelings of fatigue, but that this has not been well studied, and it found little evidence that they improve performance in endurance events. In 2010 EFSA, the EU food safety agency, concluded that less perceived effort during exercise had not been established. Its one relevant study was small and gave the BCAA group a drink with more calories than the placebo. The 2022 review reports less perceived effort with BCAAs in seven cyclists, which is the same study EFSA assessed, and no difference in 50 marathon runners.

  ODS says studies have not consistently shown that BCAAs, or any one of the three alone, enhance exercise and athletic performance. It separately notes a possibility of greater gains in muscle mass and strength during training, which the muscle claim above covers. The 2022 review did not grade its evidence. This page rates the claim evidence against, because the review concluded BCAAs do not appear to improve performance and neither authority found a consistent or established benefit.

  Sources: Source [1]Source [2]Source [3]

• In people with cirrhosis, long-term use improves survival Evidence rating: Limited

  People with cirrhosis of the liver take it hoping to live longer and stay free of complications.

  A 2023 review found longer complication-free survival with long-term BCAAs in cirrhosis, but no significant difference in overall survival, and rates its evidence low or very low certainty.

  This claim is about people who already have cirrhosis of the liver, a disease setting. A 2023 review gathered 54 studies of BCAA supplements in people with chronic liver disease, most of them done in East Asia. For people with cirrhosis who took BCAAs for at least six months, it pooled six studies for each main outcome. Survival free of events such as liver cancer, other complications or death was longer with BCAAs. It was still longer when the reviewers pooled only the four randomized trials.

  Overall survival did not differ significantly: the result just missed statistical significance, which the reviewers describe as a tendency to improve survival. Liver cancer was not significantly less common. Results on liver function, nutrition and quality of life conflicted, and the reviewers found no convincing benefit on them. After specific treatments, such as surgery for liver cancer or a liver transplant, studies mostly found no benefit or conflicting results.

  The reviewers rate almost every study at high or serious risk of bias, and their evidence low or very low certainty for every outcome. The main text does not say which outcomes are low and which very low, so this page records the lower one. They conclude that BCAAs might improve survival in cirrhosis, but that better placebo-controlled studies are needed before BCAA supplements could be advised in chronic liver disease. They also note that European liver and nutrition guidelines already advise BCAAs for some groups of people with cirrhosis.

  The review left out studies only about hepatic encephalopathy, one of the complications of cirrhosis, because a Cochrane review covers that topic. This page could not read the current Cochrane review in full, so it does not rate that use. It rates this claim limited, matching the reviewers’ low to very low certainty.

  Sources: Source [1]

How and when to take it

What the cited sources say about taking it. Ask your doctor or pharmacist what applies to you.

• A 2017 review found BCAAs seemed to help muscle damage only under specific conditions, including several days of supplements before hard exercise

  The 2017 review concluded that BCAAs seemed to help only under specific conditions, including several days of supplements starting before the exercise, and called for more placebo-controlled trials. Separately, a 2024 review of 18 trials found that a longer supplement period and a larger total amount went with a bigger drop in a blood marker of muscle damage two days after exercise; its authors say these analyses should be read with caution. Source [1]Source [2]

Which form the evidence used

Supplements are sold in several forms. This is what the sources on this page say about them — which form the research used, and any comparison those sources themselves made. Where they made none, this page does not rank the forms.

• Mixtures of leucine, isoleucine and valine, What the sources supportDetails

  The 2024 and 2017 reviews of muscle soreness and damage included only trials of the three amino acids on their own, and left out products that added other amino acids or ingredients. In the 2024 review, 12 of the 18 trials gave them in a 2:1:1 ratio of leucine to isoleucine to valine. No cited source compared ratios or products with each other, so this page cannot say that one works better than another. Source [1]Source [2]

• Leucine on its own, Details

  Leucine is one of the three BCAAs. When EFSA, the EU’s food safety agency, assessed BCAA claims in 2010, it set aside a trial of leucine alone because it did not test a BCAA mixture. A 2022 review of BCAAs in athletes calls for leucine and BCAAs to be studied separately. This page does not review evidence on leucine alone. Source [1]Source [2]

Sources

1. Attenuating Muscle Damage Biomarkers and Muscle Soreness After an Exercise-Induced Muscle Damage with Branched-Chain Amino Acid (BCAA) Supplementation: A Systematic Review and Meta-analysis with Meta-regression
   Sports Medicine - Open, 2024 · Meta-analysis · Primary source
2. Does Branched-Chain Amino Acids (BCAAs) Supplementation Attenuate Muscle Damage Markers and Soreness after Resistance Exercise in Trained Males? A Meta-Analysis of Randomized Controlled Trials
   Nutrients, 2021 · Meta-analysis · Primary source
3. Is Branched-Chain Amino Acids Supplementation an Efficient Nutritional Strategy to Alleviate Skeletal Muscle Damage? A Systematic Review
   Nutrients, 2017 · Systematic review · Primary source
4. Oral Branched-Chain Amino Acids Supplementation in Athletes: A Systematic Review
   Nutrients, 2022 · Systematic review · Primary source
5. Dietary Supplements for Exercise and Athletic Performance: Fact Sheet for Health Professionals
   NIH Office of Dietary Supplements, 2024 · Health authority summary · Primary source
6. Scientific Opinion on the substantiation of health claims related to branched-chain amino acids (BCAA) and growth or maintenance of muscle mass (ID 442, 444, 445, 447, 448, 451, 1478), attenuation of the decline in muscle power following exercise at high altitude (ID 443), faster recovery from muscle fatigue after exercise (ID 447, 448, 684, 1478), improvement of cognitive function after exercise (ID 446), reduction in perceived exertion during exercise (ID 450) and “healthy immune system” (ID 449) pursuant to Article 13(1) of Regulation (EC) No 1924/2006
   EFSA Panel on Dietetic Products, Nutrition and Allergies (EFSA Journal), 2010 · Health authority summary · Primary source
7. Systematic review with meta-analysis: Branched-chain amino acid supplementation in liver disease
   European Journal of Clinical Investigation, 2023 · Meta-analysis · Primary source · Certainty: very low

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