February 8, 2023

BCAAs (Branched-Chain Amino Acids): What You Need to Know

Major Team

What are BCAAs?

Branched-chain amino acids, or BCAAs, are a triad of essential amino acids: leucine, isoleucine, and valine. These amino acids are vital for several physiological functions, such as muscle growth and repair. They are particularly effective at reducing muscle soreness and fatigue during exercise. If you are into fitness, BCAAs are a supplement you should consider adding to your routine.[1]

What BCAAs Offer You

BCAAs can enhance muscle growth and reduce muscle fatigue and soreness, the reason why they are so popular among athletes and fitness enthusiasts. They can also be an alternative energy source in the absence of glucose. 

Other benefits
  • Weight loss. Studies indicate that BCAAs have the potential to assist with weight loss by enhancing metabolic function, as BCAAs play a significant role in muscle structure and protein synthesis.[2] When the body requires energy, such as during exercise or daily activities, metabolism increases, and fat reserves may be utilized, potentially leading to weight loss.
  • Muscle wasting. Muscle wasting is a sign of malnutrition and occurs with chronic infections, cancer, periods of fasting, and as a natural part of the aging process.[3] BCAAs account for a significant portion of the essential amino acids found in muscle proteins, and it's crucial to replace them in times of muscle wasting to halt or slow its progression. Studies support the use of BCAA supplements for inhibiting muscle protein breakdown, which may improve health outcomes and quality of life in some populations, such as older adults and those with conditions like cancer.[4] [5]
  • Liver function. BCAA supplementation may also have benefits for those with liver disease. Long-term liver damage can reduce the body's ability to absorb protein and macronutrients, leading to fatigue and weight loss. Adding BCAAs to the diet may help alleviate these symptoms and prevent further complications such as cirrhosis.[6] [7]
  • Immunity support. Intensive physical activity can lead to a weakened immune system, potentially caused by a drop in glutamine, an amino acid that fuels immune cells. BCAAs can transform into glutamine within the muscles.[8] [9]

Are There Any Side Effects?

Excessive levels of BCAAs in the blood strain the liver and kidneys, causing long-term harm. Additionally, it can interfere with insulin sensitivity and potentially lead to elevated blood sugar levels, increasing the risk of type 2 diabetes onset.[10] [11]

People with a rare genetic condition known as maple syrup urine disease should restrict their consumption of BCAAs since their bodies cannot metabolize them correctly.[12]

High levels of BCAAs also have been linked to an augmented risk of heart disease as they can contribute to the build-up of plaque in the arteries and the disruption of the balance of other essential amino acids.[13]

Bear in mind that these downsides are only from the overuse of BCAAs. Most people experience no adverse reactions when consuming the correct dosage. However, if you do experience any side effects, discontinue use and consult a healthcare professional.

How Much BCAAs Should You Take?

The recommended dosage for leucine is between 2 and 10 grams, while for isoleucine, it is 48-72 milligrams per kilogram of body weight for individuals who are not obese. More studies are required to determine the optimal dose for valine supplementation.

A combination dose of BCAAs typically involves taking 20 grams of the three amino acids with a balanced leucine and isoleucine ratio. Adequate dietary intake of BCAAs eliminates the need for BCAA supplementation.

Does the Timing Matter?

Limited research is available on the effects of taking BCAAs before or after exercise. One small study found that taking BCAAs before exercising resulted in less muscle soreness and lower markers of muscle damage.[14] Another study found no difference in body composition or strength between taking BCAAs before or after weightlifting workouts.[15]

Studies have yet to determine the optimal time to take BCAAs, suggesting that the window time for maximum muscle-building benefits from consuming protein may be as far as 5 hours after exercise. Timing of BCAA or other protein supplements may be less significant if you have eaten a meal or taken a protein supplement 1-2 hours before physical activity.[15] [16]

Taking BCAAs during endurance exercises, such as distance running and cycling, may not improve physical performance but may help reduce mental fatigue.[17]


1. Frank, K. (2023, February 1). Branched-Chain Amino Acids health benefits, dosage, safety, side-effects, and more. Examine . Retrieved February 23, 2023, from https://examine.com/supplements/branched-chain-amino-acids/

2. Blomstrand, E., Eliasson, J., Karlsson, H. K., & Köhnke, R. (2006). Branched-chain amino acids activate key enzymes in protein synthesis after physical exercise. The Journal of nutrition, 136(1 Suppl), 269S–73S. https://doi.org/10.1093/jn/136.1.269S

3. Cohen, S., Nathan, J. A., & Goldberg, A. L. (2015). Muscle wasting in disease: molecular mechanisms and promising therapies. Nature reviews. Drug discovery, 14(1), 58–74. https://doi.org/10.1038/nrd4467

4. Ko, C. H., Wu, S. J., Wang, S. T., Chang, Y. F., Chang, C. S., Kuan, T. S., Chuang, H. Y., Chang, C. M., Chou, W., & Wu, C. H. (2020). Effects of enriched branched-chain amino acid supplementation on sarcopenia. Aging, 12(14), 15091–15103. https://doi.org/10.18632/aging.103576

5. Ananieva, E. A., & Wilkinson, A. C. (2018). Branched-chain amino acid metabolism in cancer. Current opinion in clinical nutrition and metabolic care, 21(1), 64–70. https://doi.org/10.1097/MCO.0000000000000430

6. Dam, G., Aamann, L., Vistrup, H., & Gluud, L. L. (2018). The role of Branched Chain Amino Acids in the treatment of hepatic Encephalopathy. Journal of clinical and experimental hepatology, 8(4), 448–451. https://doi.org/10.1016/j.jceh.2018.06.004

7. Kawaguchi, T., Izumi, N., Charlton, M. R., & Sata, M. (2011). Branched-chain amino acids as pharmacological nutrients in chronic liver disease. Hepatology (Baltimore, Md.), 54(3), 1063–1070. https://doi.org/10.1002/hep.24412

8. Nie, C., He, T., Zhang, W., Zhang, G., & Ma, X. (2018). Branched Chain Amino Acids: Beyond Nutrition Metabolism. International journal of molecular sciences, 19(4), 954. https://doi.org/10.3390/ijms19040954

9. Negro, M., Giardina, S., Marzani, B., & Marzatico, F. (2008). Branched-chain amino acid supplementation does not enhance athletic performance but affects muscle recovery and the immune system. The Journal of sports medicine and physical fitness, 48(3), 347–351.

10. Newgard, C. B., An, J., Bain, J. R., Muehlbauer, M. J., Stevens, R. D., Lien, L. F., Haqq, A. M., Shah, S. H., Arlotto, M., Slentz, C. A., Rochon, J., Gallup, D., Ilkayeva, O., Wenner, B. R., Yancy, W. S., Jr, Eisenson, H., Musante, G., Surwit, R. S., Millington, D. S., Butler, M. D., … Svetkey, L. P. (2009). A branched-chain amino acid-related metabolic signature that differentiates obese and lean humans and contributes to insulin resistance. Cell metabolism, 9(4), 311–326. https://doi.org/10.1016/j.cmet.2009.02.002

11. Newgard C. B. (2012). Interplay between lipids and branched-chain amino acids in development of insulin resistance. Cell metabolism, 15(5), 606–614. https://doi.org/10.1016/j.cmet.2012.01.024

12. Blackburn, P. R., Gass, J. M., Vairo, F. P. E., Farnham, K. M., Atwal, H. K., Macklin, S., Klee, E. W., & Atwal, P. S. (2017). Maple syrup urine disease: mechanisms and management. The application of clinical genetics, 10, 57–66. https://doi.org/10.2147/TACG.S125962

13. Grajeda-Iglesias, C., & Aviram, M. (2018). Specific Amino Acids Affect Cardiovascular Diseases and Atherogenesis via Protection against Macrophage Foam Cell Formation: Review Article. Rambam Maimonides medical journal, 9(3), e0022. https://doi.org/10.5041/RMMJ.10337

14. Ra, S. G., Miyazaki, T., Kojima, R., Komine, S., Ishikura, K., Kawanaka, K., Honda, A., Matsuzaki, Y., & Ohmori, H. (2018). Effect of BCAA supplement timing on exercise-induced muscle soreness and damage: a pilot placebo-controlled double-blind study. The Journal of sports medicine and physical fitness, 58(11), 1582–1591. https://doi.org/10.23736/S0022-4707.17.07638-1

15. Schoenfeld, B. J., Aragon, A., Wilborn, C., Urbina, S. L., Hayward, S. E., & Krieger, J. (2017). Pre- versus post-exercise protein intake has similar effects on muscular adaptations. PeerJ, 5, e2825. https://doi.org/10.7717/peerj.2825

16. Aragon, A. A., & Schoenfeld, B. J. (2013). Nutrient timing revisited: is there a post-exercise anabolic window?. Journal of the International Society of Sports Nutrition, 10(1), 5. https://doi.org/10.1186/1550-2783-10-5

17. Blomstrand, E., Hassmén, P., Ek, S., Ekblom, B., & Newsholme, E. A. (1997). Influence of ingesting a solution of branched-chain amino acids on perceived exertion during exercise. Acta physiologica Scandinavica, 159(1), 41–49. https://doi.org/10.1046/j.1365-201X.1997.547327000.x