Quick Navigation

Branched-Chain Amino Acids

Branched-Chain Amino Acids (BCAAs) are three essential amino acids that benefit muscle growth. Because they’re present in high levels notably in animal protein, supplementation is unnecessary for most people.

Our evidence-based analysis on branched-chain amino acids features 143 unique references to scientific papers.

Kamal Patel
Research analysis led by and reviewed by the Examine team.
Last Updated:

Summary of Branched-Chain Amino Acids

Primary information, health benefits, side effects, usage, and other important details

Branched Chain Amino Acids (BCAAs) refers to three amino acids: leucine, isoleucine, and valine.

For people with low dietary protein intake, BCAA supplementation can promote muscle protein synthesis and increase muscle growth over time. Supplementation can also be used to prevent fatigue in novice athletes.

Leucine plays an important role in muscle protein synthesis, while isoleucine induces glucose uptake into cells. Further research is needed to determine valine’s role in a BCAA supplement.

Supplementing BCAAs prevents a serum decline in BCAAs, which occurs during exercise. A serum decline would normally cause a tryptophan influx into the brain, followed by serotonin production, which causes fatigue.

BCAAs are important to ingest on a daily basis, but many protein sources, such as meat and eggs, already provide BCAAs. Supplementation is unnecessary for people with a sufficiently high protein intake (1-1.5g per kg of bodyweight a day or more).

Want the unbiased truth on building muscle?

Our free muscle building mini-course teaches you what works, what's a waste of time, and advanced tips.

We cover bottlenecks, supplements that actually work, a surprising way you could be limiting your muscle gains, and what you need to do to maximize muscle building.

How to Take

Recommended dosage, active amounts, other details

The standard dosage for isoleucine is 48-72mg per kilogram of bodyweight, assuming a non-obese person. The standard leucine dosage is between 2-10g. A combination dose is 20g of combined BCAAs, with a balanced ratio of leucine and isoleucine.

Isoleucine is used for increasing glucose uptake into cells, while leucine is used to improve muscle protein synthesis.

BCAA supplementation is not necessary if enough BCAAs are provided through the diet. Further research is needed to determine valine’s optimal dosage and reason for supplementation.

Easily stay on top of the latest nutrition research

Become an Examine Member to get access to the latest research. Get 150+ studies summarized for you across 25 different categories every month.

Members also have access to the Examine Study Database of 400+ supplements and their effects on 600+ health outcomes, as well as in-depth research analyses. Understand the whole body of nutrition and supplement evidence at a glance.

Get instant access — start your free 14-day trial

Already a Member? Click here to log in.


Human Effect Matrix

Unlocked for Examine Members

Easily stay on top of the latest nutrition research

Become an Examine Member to get access to the latest research. Get 150+ studies summarized for you across 25 different categories every month.

Members also have access to the Examine Study Database of 400+ supplements and their effects on 600+ health outcomes, as well as in-depth research analyses. Understand the whole body of nutrition and supplement evidence at a glance.

Get instant access — start your free 14-day trial

Already a Member? Click here to log in.


The Human Effect Matrix summarizes human studies to tell you what effects Branched-Chain Amino Acids has on your body, how much evidence there is, and how strong these effects are.

Full details are available to Examine Members. Not a Member? Try Examine Membership completely free for two weeks.
Grade Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Level of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
Outcome Magnitude of effect
? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
Notes
grade-b
Aerobic Exercise
Minor Moderate See all 4 studies
An increase in time to exhaustion appears to exist in prolonged endurance exercise, but this benefit may only exist in untrained or lightly trained individuals. Several studies have noted that the anti-fatigue effects and increased time to exhaustion do not really occur in advanced athletes
grade-b
Fat Oxidation
Minor Low See all 3 studies
In prolonged exercise and somewhat related to the antifatigue effects, an increase in fat oxidation is noted with BCAA supplementation; this is thought to be related to the glycogen preserving effects of BCAAs.
grade-b
Fatigue
Minor Moderate See all 8 studies
A decrease in fatigue (mental fatigue when measured after the workout) results when BCAA supplementation is taken during exercise at a dose above 10g or so
grade-b
Blood Lactate (Excercise)
- High See all 3 studies
There does not appear to be any reliable or significant changes in blood lactate concentrations following exercise with BCAA supplementation
grade-c
Ammonia

Minor 		- See study
Human studies suggest time-dependent influences on ammonia (increase after exercise up until 2 hours, a reduction the next day) while animal studies suggest that overdosing BCAAs can reverse a reduction into an increase
grade-c
Processing Accuracy
Minor - See study
The increased processing accuracy appears to be secondary to reducing exercise-related fatigue, and occurs when testing is after exercise.
grade-c
Rating of Perceived Exertion
Minor - See study
There is some evidence to support a reduction in the rate of perceived exertion during exercise under the influence of BCAA supplementation, but this appears to unreliably improve performance and is of low magnitude
grade-c
Reaction Time
Minor - See study
A (beneficial) decrease in reaction time has been noted during a stimulated soccer test, which was thought to be secondary to the antifatigue effects. Hypothesized to be useful for prolonged sports
grade-c
Weight Loss
Minor - See study
The weight loss that occurs during prolonged strenuous exercise (in these examples, skiing) are attenuated with BCAA supplementation relative to carbohydrate. This is likely indicative of lean mass and/or hydration, and is not necessarily an anti-fat loss effect
grade-c
Adrenaline
- - See study
No significant influence on adrenaline concentrations
grade-c
Anaerobic Running Capacity
- - See study
No significant performance enhancing effect on short-term cardiovascular exercise
grade-c
Blood Glucose
- Moderate See 2 studies
There does not appear to be a likely alteration in blood glucose concentrations per se with BCAA supplementation, but the increased fat oxidation may attenuate the decline in glucose seen during prolonged exercise (which would appear to be a relative increase at later time points)
grade-c
Cortisol
- - See study
No significant interactions with BCAA supplementation and cortisol
grade-c
Dopamine
- - See study
Similar to the other catecholamines (adrenaline and noradrenaline), serum dopamine does not appear to be altered with supplemental BCAAs.
grade-c
Heart Rate
- Very High See 2 studies
No significant alterations in heart rate noted with BCAA supplementation at rest or during exercise
grade-c
Insulin
- - See study
No significant influence of BCAA supplementation on fasting insulin levels
grade-c
Ketone Bodies
- - See study
No significant alterations in formation of ketone bodies, which may be due to the ketogenic BCAA (leucine) being offset by the other two glucogenic ones
grade-c
Muscle Soreness
- Moderate See 2 studies
No significant influence on muscle soreness when assessed 2-3 days after exercise that is preloaded with BCAA supplementation
grade-c
Noradrenaline
- - See study
BCAA supplementation does not appear to significantly influence noradrenaline concentrations in serum
grade-c
Oxygen Uptake
- - See study
Oxygen uptake during anaerobic cardiovascular exercise does not appear to be modified with BCAA supplementation
grade-c
Power Output
- Moderate See 2 studies
Mixed effects on power output, but when it does occur it is not a per se increase in power output but secondary to reduced muscular soreness after repeated exercise. This may be more indicative of anti-fatigue effects than of genuine power output improvement

Studies Excluded from Consideration

  • Multinutrient supplement (included non-BCAA supplements)[1]

  • Confounded with non-BCAA amino acids (such as citrulline or glutamine)[2]

  • Paired with ACE inhibitors[3]

Stay on top of the latest research

To unlock the full archives of our Study Database and research analyses, become an Examine Member today.

Start your 14-day free trial

Things to Note

Is a Form Of

Primary Function:

Also Known As

BCAAs, BCAA

Do Not Confuse With

Leucine, Isoleucine, or Valine (all individual BCAAs)

  • There has been a reported stimulatory effect with BCAA supplementation, but due to a lack of research into this topic, the placebo effect cannot be ruled out as a cause.

Are you tired of all the misinformation pushed by supplement companies?

We've developed a free muscle building mini-course based on nutrition research to help you understand how to build muscle better. Learn about:

  • What supplements work
  • What supplements are a waste of time and money
  • How antioxidants could be messing up your muscle growth
  • How to maximize muscle growth

Research Breakdown on Branched-Chain Amino Acids

1Sources and Composition

1.1Sources and Structure

1.2Formulations and Variants

2Pharmacology

2.1Absorption

2.2Metabolism

3Neurology

3.1Serotonin

3.2Excitation

4Interactions with Glucose Metabolism

4.1Mechanisms

4.2Glycogen

4.3Blood Glucose

4.4Insulin Sensitivity

5Skeletal Muscle and Physical Performance

5.1Mechanisms (Skeletal Muscle)

5.2Mechanisms (Fatigue)

5.3Interventions (Aesthetics)

5.4Interventions (Fatigue)

6Interactions with Medical Conditions

6.1Amyotrophic Lateral Sclerosis (ALS)

7Safety and Toxicity

7.1General
Click here to see all 143 references.

This page is regularly updated, to include the most recently available clinical trial evidence.

Each member of our research team is required to have no conflicts of interest, including with supplement manufacturers, food companies, and industry funders. The team includes nutrition researchers, registered dietitians, physicians, and pharmacists. We have a strict editorial process.

This page features 143 references. All factual claims are followed by specifically-applicable references. Click here to see the full set of research information and references for Branched-Chain Amino Acids.

Examine.com is intended to be used for educational and information purposes only. Examine.com and its Editors do not advocate nutritional supplementation over proper medical advice or treatment and this sentiment will never be expressed through pages hosted under Examine.com. If using any pharmaceuticals or drugs given to you by a doctor or received with a prescription, you must consult with the doctor in question or an equally qualified Health Care Professional prior to using any nutritional supplementation. If undergoing medical therapies, then consult with your respective Therapist or Health Care Professional about possible interactions between your Treatment, any Pharmaceuticals or Drugs being given, and possible nutritional supplements or practices hosted on Examine.com.

Examine.com does not assume liability for any actions undertaken after visiting these pages, and does not assume liability if one misuses supplements. Examine.com and its Editors do not ensure that unforeseen side effects will not occur even at the proper dosages, and thereby does not assume liability for any side effects from supplements or practices hosted under the domain of Examine.com.

Supplements

Articles

Health Topics

Study Deep Dives

Study Summaries

Protein Intake Guide + Calculator

How to read a study

About

Never miss an update!

Your email is safe with us. We don’t share personal data.

This website is certified by Health On the Net Foundation. Click to verify.