Wheying the Benefits of BCAAs in Exercise

Andrew Reynolds and David Appleby

After hitting the gym, playing sports, or even going for a run, many athletes turn to protein and amino acid (AA) supplements to enhance muscle recovery and growth. Multiple studies suggest that individuals who regularly exercise or partake in high intensity training require more dietary protein and AAs than sedentary individuals. This additional protein not only allows the human body to repair itself, but is also required for everyday metabolic activities and immune function. Of the twenty amino acids that comprise muscle protein, nine are considered essential amino acids. These essential AAs are not able to be produced by the body on its own, and therefore must be ingested through one’s diet. While it is possible to obtain the necessary protein and nutrients through a regular balanced diet, evidence shows that supplementation before and after exercise may prove advantageous. Among the most popular and cost efficient are powdered proteins, found most commonly in the form of whey and casein. Whey protein, often referred to as “fast” protein, has been shown to elicit a sudden, rapid increase of plasma amino acids following ingestion, providing immediate delivery to the body. Casein, however, is known as “slow” protein and induces a rather progressive and prolonged increase in plasma amino acids. While the digestion of these different proteins has been found to mediate protein metabolism and synthesis after exercise, it is debated whether the use of branched-chain amino acids (BCAAs) augments these processes on its own.


The branched-chain amino acids make up approximately one third of skeletal muscle protein in the body, and account for three of the nine essential AAs. Of the three BCAAs are leucine, isoleucine, and valine, which have laid the foundation for a multi-million dollar industry of nutritional supplements. Distributors of BCAA supplements rave of their anabolic capabilities and claim of their role in muscle recovery when taken post-exercise, particularly in regard to leucine. Leucine has been said to not only act as a precursor for muscle protein synthesis, but also a regulator of intracellular signaling pathways involved in the process of protein synthesis. A few studies have reported that the ingestion of BCAAs increases protein balance either by decreasing the rate of breakdown, increasing the rate of synthesis, or a combination of both. Additionally, it was observed that pairing leucine supplements with carbohydrates and protein before and after workouts led to a heightened level of protein synthesis in the body when compared to trials where leucine was not present. However, the credibility and repeatability of the research behind these claims is unclear, and has been rebutted by other scientific studies.

In this study assessing BCAAs and muscle protein synthesis in humans, the idea that BCAAs alone are capable of promoting muscle anabolism is questioned. This claim has been put forward for more than 35 years, but has been chiefly recorded in rat and other animal studies, with almost no studies being conducted regarding the response to oral consumption. The study involves a detailed literature search, and evaluates the theoretical and empirical data used to make these initial claims regarding BCAAs. It discusses how skeletal muscle in humans comprises a much larger portion of total body mass than in rats and therefore leads to several differences in the way muscle protein synthesis is regulated. Another problem with these previous studies is that they often use the “flooding dose” technique, which involves the administration of an amino acid tracer over a very short time period, therefore neglecting any possibility of sustained effects. With that being said, many of the results found in past experiments employ methods that make the extrapolation of the data to humans unfitting and reduce the physiological significance. In addition, this study displayed how only two studies were conducted analyzing the intravenous effects of BCAAs in humans, noting in both that BCAAs decreased both muscle protein synthesis and protein breakdown. However, the rate of the catabolic processes that broke down muscle protein exceeded the rate of protein synthesis in both cases during BCAA infusion. Due to these findings, the researchers refuted the claim that consumption of dietary BCAAs initiates anabolic activity and increases muscle protein synthesis.

Overall, it is evident that additional attention to diet and supplementation is essential for athletes and individuals who regularly exercise in order to promote the growth and repair of muscles, and to maintain a healthy body. While use of protein powders in the role of muscle protein synthesis has been backed by extensive scientific research, it is still unclear of the extent to which BCAAs are capable of carrying out these same processes on their own. More studies need to be conducted in human subjects observing the activity and metabolism of proteins when dietary BCAAs are ingested to better determine the effectiveness of their use. Many factors come into play when assessing the best supplements to take in regards to exercise, including intake quantity, timing of ingestion, and interaction effects. After observing the conflicting research claims, the use of BCAAs alone may not yield noticeable results, but seems to have little to no risk involved in taking them. Many trainers and workout regimens advise the combination of protein supplements and BCAAs to maximize benefits, but the scientific research is still lacking.

Questions to Consider

  1. What would happen if an individual took more protein supplements/BCAAs than the body needed?
  2. How could studies be better designed to assess the role of BCAAs in humans?

Further Suggested Reading

[1] https://www.ncbi.nlm.nih.gov/pubmed/20048505

[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5568273/

[3] https://www.ncbi.nlm.nih.gov/pubmed/16365096/

[4] https://jissn.biomedcentral.com/articles/10.1186/1550-2783-4-8

[5] http://healthyeating.sfgate.com/primary-role-protein-diet-3403.html

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13 thoughts on “Wheying the Benefits of BCAAs in Exercise

  1. I typically use protein powder supplements after my workout, so I found the studies on BCAA’s interesting. I would like to see a follow-up study that looked at chronic adaptations to BCAA supplementation. Unfortunately I think it is difficult to compare the results found in rats to humans because of the differences in skeletal muscle percentage.

  2. I also used protein powder following my workout, but didn’t really have any information about BCAAs. I think the best results would come from humans, but most of these products seem aimed at/tested for men. Do you think there’s a difference in workout supplementation for women? Health websites try and sell “women only” BCAAs and protein powder, do you think that this is necessary? A better designed study would include both male and female subjects

    • I agree that more human studies are definitely necessary to analyze these differences between men and women. However, I don’t think that “women only” supplements are always necessary. Men are generally larger in size and have more muscle mass, meaning that the average man requires more protein per day than the average woman. While men may require more protein, I don’t believe that all women need a completely different kind of protein; just lower quantities.

  3. I’ve always been surprised how little data is out there to support BCAAs despite how big the industry for them is. My thoughts on if an individual took more than needed is that it depends partially on digestion- some would pass through the body unused and some would be digested and then stored by the body. If too many calories are being consumed it could contribute to additional fat storage. But I would say that for a lot of people taking protein supplements the goal is to bulk up and they want the extra calories.

  4. I’m surprised at the lack of research considering the popularity of protein supplements/BCAAs. I think a lot of people are under the impression that just adding more protein to their diet will help them build muscle, and they don’t really think about the effects/possible consequences. I agree that testing should be done with human subjects, and I don’t think that there’s anything wrong with that ethically since the products are already commercially available. If people did participate in trials, it would be important to control for diet and types/amounts of exercise.

    • I agree that a lot of people falsely believe that simply increasing their dietary protein intake will lead to building muscle. Numerous other factors come into play in this process including level of physical activity, diet, type of exercise program, and body type. I believe that having studies that control and group based on these factors would prove beneficial and could provide insightful results into the effectiveness of protein/BCAA supplements.

  5. I find this article to be very interesting because I have done tests on myself to see if protein powder and BCAAs had an effect on my body. I went 1 month working out every day with supplements and 1 month without supplements measuring my body mass before and after each month. I found no change in my body weight yet the same decrease in my body fat and relatively the same increase in muscle strength which I found to be very confusing because these things that are supposed to help gain weight and strength had no effect on me. I would like to see a study testing if there are some body types that have less benefits than others from workout supplements such as protein powder and BCAAs.

  6. How do you think BCAA supplementation might affect strength training vs endurance training? would it be more or less effective depending on the type of exercise you are doing?

  7. There’s not a lot of research comparing the effectiveness of BCAAs among different forms of exercise, but because of the versatility of BCAAs, I’m not sure there would be much of a difference. In the case of strength training, BCAAs may prove advantageous due to their ability to increase muscle growth, suppress muscle breakdown, and reduce DOMS. For endurance activities, the capacity of BCAAs to be broken down and used to contribute to energy production while delaying muscle fatigue would make them desirable for this category of training. If these claims are true and BCAAs really are able to reduce muscle protein breakdown and stimulate muscle protein synthesis post-exercise, I think they would prove equally beneficial for both methods of training.

  8. To my understanding, I have been told that protein is better post workout, and BCAAs are meant to be taken during a workout to promote acute muscle recovery and prolong strength and endurance of the muscles. This information was never backed by evidence, it was just what I have heard and observed from avid gym goers. I am not sure why this would work this way or why BCAAs would be more effective in the short term.

  9. I have always seen supplementation as a placebo effect and never used it because to me it seems like a waste of money. But with something so harmless and popular in todays world, Im shocked more tests haven’t been done to see if BCAAs actually make a significant difference when comparing results. It would be interesting to see if I have been wrong all these years and should be taking supplements before and after I work out.

  10. I agree that the placebo effect from supplementation seems to outweigh its true benefits. However, after in-class discussion about other types of supplementation, I am glad to see that there is some biological benefits and research to back the use of supplementation. I would be interested to see more tests done on the timing of taking these supplements, if it’s more advantageous to take BCAA’s and the like before exercise, after, or both.

  11. Greatly explained all the benefits of bcaa drink. Yes, it is true that casein protein is considered as slow protein but it has it’s own benefits. I was also planning to take bcaa supplement as pre-workout and now I’m sure it would help me a great deal.

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