Branched-Chain Amino Acids (BCAA) Facts & Uses


The chances are good that if you are serious about athletic performance, fitness, bodybuilding or building muscle, you’ve probably heard about branched-chain amino acids, also known as BCAA. The topic of BCAA inevitably comes up in discussions about building muscle and improving recovery, and for many good reasons.

What are Branched Chain Amino Acids (BCAA)?

Branched-chain amino acids are part of the essential amino acid group; because the human body cannot make them and has to get them from the diet. 

The three amino acids that make up the BCAA group are isoleucine, leucine, and valine. These three essential amino acids get grouped together because they all have a particular “branched-chain” chemical structure. 

BCAA supplements are popular because they stimulate protein synthesis and muscle growth, improve post-workout recovery, and increase stamina during workouts. They are low-cost and, in large doses, have little to no side effects.

Let’s break down the amino acids that make up the branched-chain amino acids.


Isoleucine is a hydrophobic amino acid that is in most proteins. It is, as mentioned above, part of the essential amino acid group. A few studies show that the body uses it to make hemoglobin. [1] Hemoglobin is the part of the red blood cell that carries oxygen. 

There is also some exciting research that looks at isoleucine’s ability to control blood sugar levels. [2][3] The studies indicate that it can decrease blood sugar levels to some extent. 

Probably the most important or at least the reason you are reading this, is that isoleucine can stimulate muscle growth and recovery. [3] Some studies show that isoleucine can increase the amount of glucose the muscle can take in, which aids in muscle recovery and growth. [3]

Isoleucine shows some immune system benefits. Furthermore, isoleucine studies show its ability to induce the expression of immune defence peptides like β-defensins, which can regulate the adaptive and innate immune systems.[4] 


Leucine is the most famous or well-known of the three BCAAs, and for good reason, it has many well-known and researched benefits for muscle growth. 

Leucine is critical to stimulating protein synthesis and muscle growth. It does this via signalling of the mammalian target of rapamycin (mTOR) pathway.[5][6] For leucine to stimulate mTOR, it has to be sufficiently high. If the threshold is not reached, it will not act as a signalling molecule for mTOR. Some studies suggest that the leucine threshold to stimulate mTOR, protein synthesis, and muscle growth is 2g per meal.

As with isoleucine, leucine helps regulate blood sugar. Leucine helps regulate blood sugar levels by improving the function of the insulin-secreting pancreatic β cells.[7] Research has shown that leucine can stimulate the production of human growth hormone (HGH).


Much like its other two siblings, isoleucine and leucine, valine plays a vital role as an mTOR activating compound. Studies show that protein synthesis upregulates and increases when valine concentrations increase in the body.[8] Valine on its own can increase protein synthesis and muscle growth.

Benefits of BCAA

Athletes and bodybuilders covet branched-chain amino acids because of their many benefits. Most notably on muscle protein synthesis, fatigue recovery, and exercise-induced muscle damage. A significant research portfolio now demonstrates BCAA’s ability to improve muscle growth and recovery.

Let’s dive a little deeper into the many benefits of the BCAA.

Muscle Growth

each of the individual BCAA’s can stimulate muscle growth, but the real magic happens when they are taken together in the form of a complete BCAA supplement. 

Studies show that BCAA supplements help stop muscle degradation or breakdown and stimulate protein synthesis and growth.[9] To give an idea of how much BCAAs can increase protein synthesis, let’s look at another study. The researchers gave a drink containing 5.6g of BCAA after the test subjects worked out and gave a placebo to the test subjects in the placebo group. They found that the BCAA group had a 22% increase in protein synthesis compared to the placebo group.[10]

Even though BCAA’s can stimulate or turn on protein synthesis, the body needs more to keep it going and build muscle. Just turning on protein synthesis is not enough. You have to have an ample supply of the other essential amino acids for the body to build new muscle. This is why most athletes take their BCAA supplements with a high-protein meal. Doing this ensures that they stimulate protein synthesis and have an ample supply of amino acids to build the new muscle.[11]

Increase performance and reduces exercise fatigue

Branched-chain amino acids have proven themselves in numerous studies to increase endurance and extend the amount of time it takes to reach a fatigued state when taken before working out. [12]

According to another study, participants given BCAAs during exercise registered up to 15% less fatigue than those given a placebo. [13][14]

One study might explain why BCAA’s delay fatigue. The study looked at how BCAA’s affect lipid oxidation. The study showed that BCAA increases fat oxidation when glycogen is depleted. This increase in the utilization of fat for fuel when the glycogen fuel is used up could be partly why BCAA’s increase endurance and delay fatigue. [15]

Speed up muscle recovery and decrease muscle soreness

Branched-chain amino acids help with recovery from workouts and post-workout soreness. Creatine kinase and lactate dehydrogenase, which help contribute to muscle damage, are reduced by BCAAs. In theory, this should improve recovery time and protect against muscle damage. [16] It has also been demonstrated that BCAA can reduce the perception of delayed muscle onset soreness (DMOS) by upwards of 33%, as reported by test subjects. [17][18][19]

Lowers Blood Sugar

As we have already discussed above, isoleucine and leucine have the ability to increase the functioning of insulin-producing beta cells. This leads to better blood sugar control, and more glucose gets shuttled into the muscles, thereby decreasing the circulating sugar in the blood. [20][21]

Weight control and Fat Burning

several studies show that consuming 12 to 15 grams of BCAA per day can reduce your chances of becoming overweight by as much as 30%. [22][23]

If you are looking to burn fat taking BCAA might do the trick. It was shown in a study that when BCAA are taken in combination with a calorie-restricted diet, it resulted in 3.5 more pounds lost compared to placebo. [24] another interesting study gave one group of test subjects 14g of BCAA daily and another group 28g of whey protein daily. The results showed that the BCAA group lost an average of 1% more body fat than the Whey protein group did. The BCAA group also gained on average 4.4lbs more muscle than the Whey protein group did. [25]

Side Effects of BCAA

Branched-chain amino acids are very safe, and no reported side effect profile is known, even with very high dosages that are continued for many weeks.

The only caveat to this is if you have a genetic disorder called maple syrup urine disease. Sufferers of this disease cannot break down certain amino acids. [26]

BCAA Dosage

BCAAs do not have an official recommended daily allowance from any governmental health agencies. Studies suggest that different amounts should be taken each day. [27][28] The dosage should vary depending on your goals and reason for taking it. Also, you should consider starting at lower dosages to ensure you do not experience any gastrointestinal upset. It is also crucial that you consult with your doctor before you start taking any BCAA supplement to ensure it is safe for you.

When is the best time to take a BCAA supplement?

The optimal time to take BCAA supplements is both before and after a workout. Some users who are focused on gaining muscle also supplement with them during or intra-workout. Others take them throughout the day to try and maintain an anabolic environment and prevent muscle breakdown. [9][10]

There is not a lot of research examining the perfect timing of BCAA administration in terms of muscle growth. This is where you will have to experiment to see what gives you the best results in terms of muscle growth.

Dietary Sources of BCAA

  • Fish
  • Meat
  • Chicken
  • Beans
  • Seeds
  • Nuts
  • Eggs
  • Dairy
  • Quinoa

Summary of Branched-chain amino acids

Branched-chain amino acids are a solid supplement to add to your supplement regimen if you are looking to prevent muscle breakdown and increase muscle mass.

With that being said, BCAA supplements are not a magic pill, and just by taking them, you will not explode with muscle. This supplement has to be combined with proper training and diet to ensure that you get the maximum benefits.


  1. Specialization of Rabbit Reticulocyte Transfer RNA Content for Hemoglobin Synthesis (
  2. Effects of Leucine and Isoleucine Infused Intrapancreatically on Glucagon and Insulin Secretion | Endocrinology | Oxford Academic (
  3. Effects of isoleucine on glucose uptake through the enhancement of muscular membrane concentrations of GLUT1 and GLUT4 and intestinal membrane concentrations of Na+/glucose co-transporter 1 (SGLT-1) and GLUT2 | British Journal of Nutrition | Cambridge Core
  4. Isoleucine Plays an Important Role for Maintaining Immune Functio…: Ingenta Connect
  5. Leucine and Protein Synthesis: mTor and beyond | Nutrition Reviews | Oxford Academic (
  6. Leucine-Enriched Nutrients and the Regulation of mTOR Signalling and Human Skeletal Muscle Protein Synthesis (
  7. Leucine metabolism in regulation of insulin secretion from pancreatic beta cells | Nutrition Reviews | Oxford Academic (
  8. Regulation of protein synthesis in porcine mammary epithelial cells by l-valine | SpringerLink
  9. Branched-chain amino acids activate key enzymes in protein synthesis after physical exercise – PubMed (
  10. Branched-Chain Amino Acid Ingestion Stimulates Muscle Myofibrillar Protein Synthesis following Resistance Exercise in Humans – PubMed (
  11. Activation of mTORC1 by leucine is potentiated by branched-chain amino acids and even more so by essential amino acids following resistance exercise – PubMed (
  12. Effects of Oral Branched‐Chain Amino Acids (BCAAs) Intake on Muscular and Central Fatigue During an Incremental Exercise (
  13. Influence of ingesting a solution of branched-chain amino acids on perceived exertion during exercise – PubMed (
  14. Effects of branched-chain amino acids supplementation on physiological and psychological performance during an offshore sailing race – PubMed (
  15. Branched-chain amino acids supplementation enhances exercise capacity and lipid oxidation during endurance exercise after muscle glycogen depletion – PubMed (
  16. Effects of branched-chain amino acid supplementation on serum creatine kinase and lactate dehydrogenase after prolonged exercise – PubMed (
  17. Branched-chain amino acid supplementation before squat exercise and delayed-onset muscle soreness – PubMed (
  18. Exercise-induced muscle damage is reduced in resistance-trained males by branched-chain amino acids: a randomized, double-blind, placebo controlled study – PubMed (
  19. Branched-chain amino Acid plus glucose supplement reduces exercise-induced delayed onset muscle soreness in college-age females – PubMed (
  20. Leucine metabolism in regulation of insulin secretion from pancreatic beta cells (
  21. Leucine Stimulates Insulin Secretion via Down-regulation of Surface Expression of Adrenergic α2A Receptor through the mTOR (Mammalian Target of Rapamycin) Pathway (
  22. The Ratio of Dietary Branched-Chain Amino Acids is Associated with a Lower Prevalence of Obesity in Young Northern Chinese Adults: An Internet-Based Cross-Sectional Study (
  23. Higher branched-chain amino acid intake is associated with a lower prevalence of being overweight or obese in middle-aged East Asian and Western adults – PubMed (
  24. Combined effects of caloric restriction and branched-chain amino acid supplementation on body composition and exercise performance in elite wrestlers – PubMed (
  25. Consuming a supplement containing branched-chain amino acids during a resistance-training program increases lean mass, muscle strength and fat loss (
  26. Maple syrup urine disease: mechanisms and management (