What are Branch Chain Amino Acids?
The Branch Chain Amino Acids consist of three separate amino acids: Leucine, Isoleucine, and Valine. These amino acids are considered “essential” because the body cannot manufacture them and thus, they must be obtained from our diet. Leucine helps in the regulation of protein turnover and energy metabolism. It also helps inhibit the breakdown of muscle protein that occurs after high stress. Isoleucine’s main purpose is that of an antioxidant. Finally Valine improves energy metabolism and protein synthesis, and like Leucine, helps maintain muscle strength during times of high intensity physical stress. Branch chain amino acids are found in high concentrations primarily in the skeletal muscle tissue. These BCAAs account for 35-40% of the dietary essential amino acids in body protein and 14-18% of the total amino acids in muscle proteins.
What do they do?
As our muscles burn up the available stores of BCAA’s in the body during exercise, they begin to break down skeletal muscle tissue in order to provide the essential amino acids to fuel more exercise. This cell damage results in reduced ability to contract and relax during intense stress, resulting in muscle fatigue, lactic acidosis, loss of performance and delayed recovery as muscle tissue repairs itself. Generally, these branched chain amino acids are muscle synthesis, muscle growth, and muscle repair. More specifically these BCAA’s perform numerous functions, though they are not used as a primary energy source (as shown above), they are definitely an important fuel source for skeletal muscle during periods of extreme exertion. During these periods of stress, BCAAs help promote protein synthesis while helping to suppress its catabolism and serve as substrates for gluconeogenesis. The catabolism of the BCAAs in skeletal muscle plays a key role in the formation of glutamine which is one of the glucogenic amino acids. Other functions include; increased endurance resulting in delayed fatigue during exercise, improved mental performance, energy levels, immune system function, and finally, post exercise recovery. Post exercise recovery means less muscle soreness and fewer upper respiratory tract infections.
In terms of skeletal muscle building and post exercise muscle recovery, many experiments have been done to the look at the effects of BCAAs. For example, one experiment gave branched chain amino acids or a placebo to 7 subjects during 1 hour of cycle ergometer exercise and during a two-hour recovery period. The intake of the BCAA did not influence the rate of exchange of the aromatic amino acids during exercise or increase their muscle concentration. However, during the recovery period, a faster decrease of the concentration of the aromatic amino acids was found within the BCAA group. The results suggest that BCAA have a protein-sparing effect during the recovery after exercise, either that protein synthesis has been stimulated and/or protein degradation has decreased.
A second test was given to 14 healthy male and 16 healthy female adults, between the ages of 21-24 years old, who do not participate in regular exercise. The test performed were squats to induce delayed onset muscle soreness (DOMS) and muscle fatigue. Subjects were given either a BCAA mixture or a placebo that was to be consumed 15 minutes prior to exercise. The results of this study indicate that the ingestion of the 5g of BCAAs previous to exercise can reduce DOMS and muscle fatigue for several days after exercise.
One study gave a group of trained triathletes 6g of BCAA per day for one month prior to competition, then 3g of BCAA from the day of competition to a week after. As compared with a placebo group timing the placebo for the same length of time, the BCAAs restored depleted glutamine stores and immune factors that occur in elite athletes. This study also suggested that may improve exercise induced declines of mental functioning.
Lastly, one study tested 13 subjects whom ingested either a BCAA mixture or a placebo prior to endurance exercise in the heat. On average, the BCAA group cycled 153.1 minutes while the placebo group only cycled for an average of 137.0 minutes.
Most diets contain an adequate amount of BCAA ingestion, which is between 25-65 mg per 2.2 lbs. of body weight. Many human studies a dose of >5 g of BCAA was used as a supplement, the minimum dose to produce a beneficial effect remains to be clarified, thus the effective ratio of the three BCAAs remains uncertain. Toxicity studies of BCAAs using animals showed that BCAAs are quite safe amino acids when the three are taken in a ratio of 2:1:1(leucine: isoleucine: valine). For use before and during exercise, effective doses for delaying central fatigue have been shown at a range of 10-20 grams/day in separate doses. For use post exercise to enhance muscle recovery, 750-1500 mg of BCAA or a 3:1:1 ratio (leucine: isoleucine: valine) has been shown to reduce muscle soreness and improve energy/fatigue levels. However, athletes involved in intense training often take 5g of leucine, 4g of valine, and 2g of isoleucine per day to prevent muscle loss and increase muscle gain (though most research does not support this type of use).
Thus far, no significant adverse side effects have been shown from BCAA supplementation. One study showed that a large amount of BCAA supplementation (60mg) caused changes in blood levels of tryptophan, phenylalanine, and tyrosine. Alterations in these blood levels could ultimately cause depression in susceptible individuals. As of now, intakes of BCAA’s up to 40g per day in tablet form and 1-7g per liter in liquid form with no side effects. However, some people experienced stomachaches or other minor gastrointestinal problems such as cramps or diarrhea at levels above a few grams/dose.
With so many studies suggesting that BCAA supplementation prior to exercise has a protein sparing effect, with either protein synthesis being stimulated and/or protein degradation being inhibited; it is hard to not recommend them. Also, because no serious adverse side effects have been shown, it seems like unless taken in toxic levels, fairly safe.
- Shimomura, Yoshiharu, et al. "Exercise Promotes BCAA Catabolism: Effects of BCAA Supplementation on Skeletal Muscle during Exercise." The Journal of Nutrition (2004): 1583S-1587S.
- Shimomura, Yoshiharu, et al. "Nutraceutical Effects of Branched- Chain Amino Acids on Skelelal Muscle." The Journal of Nurtrition (2006): 529S-532S.
- Blomstrand, Eva, et al. "Branched-Chain Amino Acids Activate Key Enzyme in Protein Synthesis After Physical Exercise. The Journal of Nutrition (2006): 269S-273S.
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_Aminos. April 6, 2007.
–Reprinted with Permission