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First off, what are amino acids? I know, this is the real basic stuff, but it helps to review before moving on to the numerous supplements that contain amino acids or their metabolites. If you can go back to high school for a moment you’ll recall that amino acids are the building blocks of proteins. There are 20 different amino acids, nine of which are deemed “essential” amino acids. Now that doesn’t mean they are better than the other eleven. It just means that we HAVE to ingest those nine little guys from outside food sources. The other eleven are also found in protein containing foods however they can  be synthesized in the body from other compounds as well. For example, arginine can be made from glutamate. Therefore glutamate is essential, however arginine is not. There are certain situations, such as illness, when nonessential amino acids do need to be supplemented, but that is a different topic for another time.


Now, when we work out our goal is to gain muscle mass. In order to do this we have to break down the existing muscle and build it back up again. Clearly we need those amino acid building blocks to get into our little muscles and pump them up. We are trying to enhance muscle protein synthesis and decrease muscle protein breakdown, or at least have a higher rate of synthesis to breakdown.  


So what’s the deal with branched chain amino acids anyway? This is just another in the long line of supplements that has been touted to benefit recovery from intense exercise.Branched chain amino acids (BCAAs) include leucine, isoleucine, and valine. They are three of the nine essential amino acids. If you search online for branched chain amino acids you will see a number of claims stating that they increase muscle mass, combat fatigue, increase endurance, and decrease muscle soreness. But what is the evidence? I would love to believe that there is something out there that can help me gain an advantage in training, but I’m not willing to throw my money away at unproven supplements. So I’ve done some research and this is what I have found.



Increased Protein Synthesis and Decreased Protein Degradation


Resistance exercise increases muscle mass when there is a higher rate of protein synthesis to protein breakdown, as noted above. Resistance exercise improves the net balance by stimulating muscle protein synthesis, but nutrient intake is required for an anabolic response. Protein synthesis can increase for 24 hours and even up to 48 hours after a workout (1,2). Studies looking at muscle biopsies, protein kinetics, and amino acid transport also show that intake of amino acids immediately following exercise may be more beneficial than at a later time due to enhanced blood flow and increased uptake(3,4). Intake of protein following resistance exercise stimulates protein synthesis at a greater rate than protein degradation. This is seen with protein intake in general, such as with whey and casein intake (8). So why do we specifically need a BCAA supplement if we can just stick to our whey protein shake? Studies have shown that BCAA appear to activate key enzymes leading to protein synthesis after exercise (12). One of the BCAAs, leucine, has been noted as an amino acid that has an anabolic effect on muscle by increasing protein synthesis and decreasing protein breakdown. This is based on muscle biopsy studies looking again at the uptake of leucine (5,6). And while all amino acids are important for muscle synthesis, there have been studies showing that BCAA, in particular leucine, may have even more of a stimulatory effect on post exercise muscle uptake of amino acids. One interesting study on eight men (yes I know, a small sample size, but all of these studies are small at this time) had each subject randomly assigned to three trials; one in which they received either a carbohydrate drink 45 minutes after exercise, a carbohydrate and protein drink, or a carbohydrate/protein/free leucine drink. The trials with the carbohydrate/protein and carbohydrate/protein/free leucine drink showed higher protein synthesis and lower protein degradation rates than the carbohydrate group. Additionally, the fractional synthetic rate of protein was highest in the carbohydrate/protein/free leucine group. It was at an intermediate value in the carbohydrate/protein group and lowest in the carbohydrate only group. So while adding protein in general to post exercise nutrition seems to enhance muscle synthesis, there is at least some evidence that there may be an additional additive effect of free leucine (7).



Increase Endurance and Decreased Muscle Soreness


BCAA have also been studied in endurance sports and it appears that they may have a beneficial effect more in the recovery period than during training. These studies were based on indirect markers however and seemed to indicate that BCAAs contribute to decreasing protein breakdown more than increasing synthesis in the recovery period following endurance activities (9,10). A more recent study showed decreases in markers of muscle breakdown in subjects given BCAA prior to exercise (11). This is an important consideration, especially for someone like myself who can sometimes push the limit with exhaustive endurance activities. Recovery between training is critical, and if there is a way to help ameliorate the rate of muscle breakdown this can go a long way in being able to fully recover between training sessions. There is also evidence that BCAA supplementation may also alleviate muscle damage, with a study showing that BCAA supplementation reduced muscle soreness following damaging exercise. However, there was no discernible impact on muscle function in that study (13).



Decreased Exercise Fatigue


For anyone involved in ,performance sports fatigue is a crucial limiting factor. Studies have shown that increased serotonin levels lead to reduced performance while increased dopamine levels are correlated with improved performance (14). BCAAs are utilized during exercise, and when these levels drop in the blood, tryptophan levels rise. Tryptophan is a precursor to serotonin, therefore this raises serotonin levels. In theory, BCAA would decrease tryptophan generation and therefore serotonergic activity,  thereby decreasing perceived exertion and fatigue. One study did show that during 60 minutes of exercise at a given work rate the study subjects ratings of perceived exertion when they were given BCAAs were 7% lower, and their ratings of mental fatigue were 15% lower than when they were given placebo (15). Another study showed decreased perceived exertion, although no significant improvement in performance. However, this trial was done in untrained males (16). 



Bottom Line

Okay…what does it all mean? Well first of all, these are just a few of the many studies that have been done with probably countless more in the works. I think it’s pretty safe to say that protein intake following exercise, likely within a 45 minute time period, is beneficial to positive protein balance and increased protein synthesis. This protein can come in many forms and I always stress the importance of whole food sources of nutrients, although in a pinch protein supplements definitely play a big role which I discuss in a different article. High quality protein will ideally already contain all the essential amino acids, including BCAAs. So the real question is, do you really need a separate BCAA supplement?  I don’t think there is a yes or no answer, but more of “it depends.” This goes with everything in nutrition, as nothing is one size fits all. The trial I mentioned above that did not show improved performance was done in untrained subjects, so would these results be different in trained athletes? Hopefully future research will help to glean out these details.  I personally do use a BCAA supplement. I have a very heavy training load and if I might even have a small benefit from decreasing muscle degradation and muscle soreness, and lowering perceived level of exertion, I’ll take it. There are many days where I will do cardio in the morning and a weight session at night, and I typically will use a BCAA supplement prior to my AM cardio and during my PM weight session. I know I wouldn’t be able to digest a full protein shake or solid food during my workout or immediately prior to my cardio, and mixing some BCAAs with my water is a quick way to ingest these amino acids.  If you are only working out a few days a week or have a lighter load you may not see the benefit of adding an additional supplement, although I do stress still making sure you are getting an adequate intake of high quality protein. I think there is definitely more research to be done in this area and I am excited to see what is to come in this field in the future.






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