BCAAs (branched chain amino acids), leucine, isoleucine, and valine, are three of the nine essential amino acids (EAAs), meaning our body cannot synthesize them, so we must consume them in our diet. BCAAs are present in complete protein sources such as animal proteins (eggs, dairy, poultry, meat, fish) as well as in soy. Many sports nutrition foods and protein powders have added BCAAs and whey and soy protein powders provide all the EAAs including BCAAs.
BCAAs are unique in that they are the only amino acids that the muscle can directly take up and utilize for energy. As glycogen depletes leucine oxidation increases; however, the amount of BCAA oxidation is still generally small during prolonged endurance exercise (>90 min), compared to carbohydrate and fat. BCAAs are also important for triggering the anabolic process of muscle protein synthesis (MPS), although leucine appears to be the primary driver for this. Finally, BCAAs have been suggested to counteract aspects of “central fatigue”.
Like all amino acids, BCAAs flux in and out of the body’s amino acid pool and are used by the body as needed based on the relative demand. Provided an athlete is ingesting adequate protein in their diet and eating high-quality proteins that provide all EAAs, there should be a sufficient amount of BCAAs available in the AA pool for the body to use when needed. In theory, supplementing with BCAA during endurance efforts could support BCAA oxidation, possibly delaying fatigue and improving performance or exercise capacity. However, there is a lack of evidence to suggest that BCAA supplementation actually improves performance. If an athlete is not able to regularly meet protein needs through the regular diet, it is possible that supplementing with BCAAs or with protein and carbohydrate during exercise could be beneficial, especially if the athlete is not meeting during-exercise carbohydrate needs.
Regarding MPS and recovery, leucine is the primary driver of the anabolic response. Likewise, if an athlete is ingesting sufficient protein in the regular diet with adequate leucine, BCAA supplementation is likely not necessary. Research examining the effect of BCAA supplementation compared to a placebo does indicate elevated markers with respect to MPS response, but when compared to a complete protein like whey, BCAAs do not appear to perform better.
Factors related to central fatigue during prolonged exercise are complex and it has been suggested that exercise-induced increases in serotonin may contribute to sensations of fatigue. In theory, it might be expected that BCAA ingestion can blunt the increase in serotonin, thereby decreasing fatigue factors. However, research has been inconclusive in this area and fatigue remains a complex phenomenon.
If you regularly fall short on your protein intake, it would be worth trying supplementation with a complete protein supplement that is high in EAAs and BCAAs like whey. There may be days when you do very long training sessions (or ultra-distance races) and it’s not possible to ingest all your daily protein in regular meals. In this case, you may consider trying a BCAA supplement during exercise and then ingest a high-quality recovery drink and meal ASAP post-exercise. Again, the response to BCAA supplementation is generally equivocal in the literature but you may find that it works for you.
A BCAA supplement may contain ~1.7-3.5 g leucine per serving. For reference, 20-25 grams of whey protein would also provide the recommended amount of leucine.
Taking current evidence into consideration, it makes sense to
Hit your daily protein target by choosing complete protein sources and complementary plant protein sources as often as possible. Both quantity and quality matter!
Eat a mixed meal (carbohydrates with some protein) prior to training
Take in the recommended amount of carbohydrate per hour (as best you can)
Try adding BCAA or protein+carb if you cannot meet your during-exercise carb needs (e.g. during ultra-endurance activity)
Consider additional strategies to help performance, for example there is strong evidence that caffeine combined with carbohydrate may improve performance and counteract central and peripheral fatigue factors. However, if you feel like BCAAs provide a benefit to you as well, the psychological edge may be worth it.
PMID: 22150425, 33106933, 18577773, 24791922, 30854370
