<body><h1>Branched-Chain Amino Acids (BCAA)</h1><p><span style=”color: black;”> </span></p><p><span style=”color: black;”> syn. leucine, isoleucine, and valine</span></p><p><span style=”color: black;”> <div id=’imgblock’><img data-pointer=’9096’/></div></span></p><h2><span style=”color: black;”>Description: </span></h2><p> Leucine, isoleucine, and valine are known as branched-chain amino acids (BCAA). These amino acids are highly prominent in muscle, and account for 14-18% of its total amino acid content.160,161 BCAAs are used as more than just components for building muscle proteins. These amino acids appear to directly influence protein metabolism, both by stimulating protein synthesis and inhibiting protein degradation.162 BCAAs may also influence muscle energy metabolism,163 support the immune system,164 reduce fatigue,165 and diminish post-exercise muscle soreness.166 Exercise enhances the breakdown of BCAAs, which may increase dietary requirements.167 Branched-chain amino acid supplements are widely used in sports nutrition to enhance muscle growth and recovery from intense exercise. </p><p></p><p class=”ql-align-right ql-direction-rtl”><div id=’imgblock’><img data-pointer=’7006’/></div></p><p class=”ql-align-right ql-direction-rtl”></p><p>Branched-chain amino acids appear to increase muscle protein retention via several mechanisms. To begin with, BCAAs (particularly leucine) have been shown to stimulate the anabolic signaling pathway mTOR, and as a result its downstream target protein p70 S6 kinase, which are considered integral to muscle hypertrophy.168 BCAAs also result in the stimulation of eukaryotic initiation factor 4E-binding protein (4E-BP1) and extracellular signal-related kinase (ERK 1/2), also linked to positive adaptive responses to training. However, some of these effects may not be maintained by leucine alone, thereby, supporting the need for complete BCAA supplementation.169 Human studies also suggest that BCAA supplementation might increase plasma growth hormone levels, another positive mediator of muscle protein synthesis.170</p><p> BCAAs also appear to be strong inhibitors of muscle protein catabolism. Exercise has been shown to increase both muscle protein synthesis and breakdown rates. When proper nutrition is supplied, the balance should favor protein synthetic processes and muscle growth. Still, reducing the level of protein breakdown may result in a higher net protein gain. Studies have shown that the supplementation of branched-chain amino acids before or during intense exercise can significantly reduce protein breakdown, resulting in a tissue sparing effect.171,172,173 Other studies have shown that when BCAAs are taken before and after training, markers of muscle breakdown were reduced for up to five days following exercise.174,175 This suggests that there is an extended (as opposed to only acute) anticatabolic effect on muscle protein. </p><p> BCAAs are also involved in muscle energy metabolism, both as direct energy providers and by preserving other energy substrates. Unlike the standard amino acids, which are mainly oxidized in the liver, branched-chain amino acids are readily oxidized in the muscles for energy.176 A portion of the energy expended during high intensity exercise comes from the oxidation of BCAAs. Adequate BCAA levels may enhance muscle energy production, increase carbohydrate availability, and preserve muscle and liver glycogen stores.177 Branched-chain amino acids may also lower the buildup of lactate during exercise, which is known to reduce endurance and slow recovery.178</p><p> Clinical and empirical evidence supports the use of branched-chain amino acids with both aerobic and anaerobic exercise. When taken before or during a period of intense training, BCAAs appear to reduce the rate of protein degradation (helping to preserve muscle). Branched-chain amino acids also tend to improve muscle soreness and tissue recovery in the days following exercise. When taken with a standard protein and carbohydrate drink during the post-exercise recovery period, BCAA supplementation can also enhance total protein retention beyond the intake of a protein/carbohydrate drink alone. In summary, BCAAs may have a tangible role in increasing muscle mass and strength following weight training, and improving recovery and possibly even performance during endurance activities. </p><h2> Promoted Benefits:</h2><p> Branched-chain amino acids are promoted to increase muscle mass and strength, improve recovery and soreness following exercise, and enhance overall athletic performance. </p><h2> Clinical Studies: </h2><p> Branched-chain amino acids have been shown to improve performance in placebo-controlled studies with trained adults. They have a Clinical Support Rating of 5 (5/5).</p><p> One placebo-controlled study monitored performance improvements in trained athletes and the effects of BCAA supplementation in cross-country and marathon runners.179 The supplement was taking during active exercise. While no improvements were noticed in the higher performing athletes, the use of branched-chain amino acids improved running performance in the slower group of marathon runners (3:05 – 3:30 run time) compared to the use of a placebo. It also appeared to increase the retention of amino acids in the muscles. Branched-chain amino acids also reduced signs of mental fatigue in the cross-country runners during a 30-km race.</p><p> Another placebo-controlled study found BCAA supplementation to improve exercise performance during heat stress in a group of healthy untrained men and women.180 Each subject took the branched-chain amino acid drink (or a placebo) every 30 minutes during exercise, which consisted of cycle ergometer training at 40% peak oxygen consumption (VO2peak) until the point of exhaustion. The use of a branched-chain amino acid supplement resulted in a significant improvement in time to exhaustion compared to placebo (153.1 min versus 137 min), which represents a notable improvement in endurance performance. </p><p> An additional placebo-controlled study looked at the effects of acute and chronic BCAA supplementation on energy metabolism and exercise performance in a group of healthy untrained men.181 The subjects took a dose of 14.4 grams per day for the acute part of the study, which was taken on two separate occasions before exercise evaluations (forearm grip exercise). BCAA supplementation was shown to significantly improve cardiovascular performance (respiratory quotient) compared to placebo in this part of the study. During the chronic supplementation study, 14.4 grams of BCAA were taken daily for 30 days. Here, the use of BCAAs significantly improved muscle strength (grip strength) compared to placebo, without significantly affecting muscle size. </p><p> Exercise studies with branched-chain amino acids have had conflicting results. Some have failed to find statistically significant improvements in exercise performance following supplementation182,183 , or have found BCAAs to be comparable to the use of a simple carbohydrate supplement.184 Whether these inconsistent results are due to individual variances, study methodological difficulties, or specific circumstances in which BCAAs can exert tangible ergogenic effects remains unclear. Further study is needed to better understand the potential role of branched-chain amino acids in improving exercise performance.</p><p> The positive effects of branched-chain amino acids on muscle protein kinetics following anaerobic exercise appear to be well supported. One commonly cited placebo-controlled study examined the effects of the branched-chain amino acid leucine on protein synthesis and retention following resistance training in a group of healthy untrained subjects.185 The leucine was added to a whey protein/carbohydrate recovery drink. The study also examined the same protein/carbohydrate drink without leucine, as well as a carbohydrate only drink. The exercise protocols consisted of eight sets each of leg press and leg extensions, which were performed at an ~80% 1-rep maximum weight for approximately 8 reps each. Subjects consumed the supplemental drink every 30 minutes after training, for a total of 6 hours. Measures of protein kinetics were taken at various points over this 6-hour window. The BCAA-enriched drink resulted in the greater overall retention of muscle protein. chain amino acids have become very popular with many types of both power and endurance athletes. Most consistently, the supplement seems to decrease the total time for muscle recovery, as well as soreness levels. This allows for a more frequent training schedule, and greater level of stimulus in a variety of activities. With regard to weight training specifically, BCAAs have become very popular anabolic support supplements. In most instances, the user can attribute a greater level of muscle gain when adding BCAAs to their regular supplementation schedule. It is commonly taken prior to or during exercise to reduce muscle damage during training, and immediately after to support muscle recovery. A small percentage of users report insufficient results with BCAAs, usually finding that they work no better than regular protein. It may simply be that in some circumstances BCAAs fail to provide sufficient (noticeable) improvements. Overall, branched-chain amino acids have an Empirical Evidence Rating of 5 (5/5).</p><h2> Effective Dosage: </h2><p> Based on clinical studies, a dosage of 5-20 g per day is recommended. BCAA supplements typically contain a similar amino acid balance to that found in animal proteins, consisting of a 2:1:1 ratio of leucine, isoleucine, and valine.</p><p> BCAAs can be taken before or during training to reduce muscle catabolism during exercise, or after training to support recovery. It may be most effective to supplement BCAAs both at the onset of (or during) exercise, and during the post-exercise recovery period. </p><h2> Empirical Evidence: </h2><p> BCAAs have been widely used as stand-alone nutritional supplements. The feedback on this type of supplement as an ergogenic aid has been strongly positive. As a result of their high efficacy, branched chain amino acids have become very popular with many types of both power and endurance athletes. Most consistently, the supplement seems to decrease the total time for muscle recovery, as well as soreness levels. This allows for a more frequent training schedule, and greater level of stimulus in a variety of activities. With regard to weight training specifically, BCAAs have become very popular anabolic support supplements. In most instances, the user can attribute a greater level of muscle gain when adding BCAAs to their regular supplementation schedule. It is commonly taken prior to or during exercise to reduce muscle damage during training, and immediately after to support muscle recovery. A small percentage of users report insufficient results with BCAAs, usually finding that they work no better than regular protein. It may simply be that in some circumstances BCAAs fail to provide sufficient (noticeable) improvements. Overall, branched-chain amino acids have an Empirical Evidence Rating of 5 (5/5).</p><h2> Side Effects / Safety: </h2><p> Branched-chain amino acids were well tolerated during clinical studies, with no significant side effects reported. Higher doses may cause gastrointestinal distress (nausea, diarrhea etc.).</p><p> </p><p> </p><p><span style=”color: black;”> </span></p></body>
