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The Science of BCAAs

What are BCAAs?

Branched chain amino acids or BCAAs are a subgroup of the essential amino acids. Out of the 9 essential amino acids which we require from food sources due to an inability of our bodies to create them, 3 of those are BCAAs – leucine, valine and isoleucine. What separates BCAAs from the other essential amino acids besides the name is that they have branching side chains, hence their name.

BCAAs make up just over a third of all amino acids present in muscle and unlike other essential amino acids are metabolised in the muscle rather than in the liver. During exercise, the breakdown of BCAAs is increased and combining this with the fact that we cannot generate our own BCAAs, the requirement for BCAAs is seen as even more relevant in frequent exercisers and very active people. A Quick Look at The Biochemistry1: the breakdown of BCAAs in the body is complex and going into it in full detail will probably turn everyone off this article. However it is important to understand how it occurs so we can appreciate how much we require it. The entire catabolic pathway of BCAAs is located in the mitochondria, a special component of our cells. The first two steps of BCAA breakdown are common for all three BCAAs. Firstly, all BCAAs are transaminated to BCKA (branched chain keto acids). These BCKAs then undergo a second process whereby they are converted to coenzyme A (CoA), which is then used primarily as a fuel for energy production. The second reaction is made faster by a complex known as the BCKDH (branched chain α-keto acid dehydrogenase). In order for this complex to work however, there needs to be a low level of a special enzyme called BCKDH kinase.

So: Step 1: BCAA >> BCKA
Step 2: BCKA >> CoA
BCKDH makes step 2 faster
BCKDH Kinase makes step 2 slower

It has been shown that endurance exercise will activate the BCKDH complex which will in turn lead to increased levels of BCAA breakdown. Furthermore, the breakdown of leucine will produce a molecule called KIC (α-ketoisocaproate), which will strongly inhibit BCKDH kinase. Exercise has been shown to increase levels of free leucine and KIC in skeletal muscle which has been suggested as one of the primary reasons for large muscle BCAA breakdown. Because BCAAs make up the largest amino acid component of skeletal muscle, the muscle protein degradation from exercising will contain a lot of BCAAs. Therefore the need to replenish these BCAAs is paramount. It has also been shown in animal studies that BCAA breakdown is increased even in a BCAA deficient state, so without adequate replenishment, you could be depleting your BCAA levels even more the next time you exercise.

BCAAs – The Good News

BCAA supplements has been around for a while and for good reason. Standalone BCAAs have been implicated to have several ergogenic effects. Let’s have a quick look at some of these:  

  • BCAAs & Improved Recovery
  • BCAA supplementation has been shown in a few studies to help with muscle soreness experienced after exercise. Muscle soreness can inhibit our ability to train effectively and more frequently.
  • Matsumoto et al (2009)2 examined 12 long distance runners and gave them either a placebo isocaloric drink or a drink containing 0.8% BCAAs. Indicators of muscle damage and inflammation were reduced by up to 21% in the case of creatine kinase and subjective feelings of muscle soreness and fatigue were also reduced for those consuming the drink with BCAAs.
  • Shimomura et al (2010)3 was able to show similar decreases in subjective feelings of muscle soreness in 12 untrained females performing a few sets of squats, an extremely effective exercise in causing DOMS (delayed onset muscle soreness). Furthermore, Shimomura found less evidence of muscle damage in those consuming a BCAA supplement.
  • Jackman et al (2010)4 was able to demonstrate that non weight trained males who took around 30g/day of BCAAs were able to reduce feelings of muscle soreness, however was unable to reduce decreased performance due to heavy exercise induced muscle damage.

Summary: Supplementation with BCAAs may help reduce markers of muscle damage and inflammation suggesting less muscle damage. Supplementation with BCAAs may also help reduce subjective feelings of muscle soreness which can promote faster return to exercise, a known method to further reduce muscle soreness.

BCAAs and Anti-Catabolic Effects

As mentioned before in the Matsumoto study, ingestion of BCAAs was able to lead to decreased levels of muscle damage as shown by reductions in several indicators of muscle damage including creatine kinase, lactate dehydrogenase and granulocyte elastase.

  • Sharp and Pearson (2010)5 were able to show that consumption of a high BCAA (3.3g) amino acid supplement was able to not only decrease creatine kinase levels in 4 resistance trained males performing high intensity resistance training, but also curbed the rise of cortisol, a known catabolic hormone. Furthermore, blood levels of testosterone were higher in those taking a high BCAA supplement.
  • Greer et al (2007)6 and Coombes & McNaughton (2000)7 were able to find similar statistically significant decreases in enzymes which are elevated with muscle damage with BCAA supplementation.
  • In addition, Carli et al (1992)8 was able to show that BCAAs was able to attenuate decreases in testosterone levels throughout a bout of exercise, which could ultimately suggest a decreased catabolic profile post exercise. Supplementation with BCAAs can also slow down muscle protein breakdown as they can be used as fuel sources themselves during the work out.

Summary: Supplementation with BCAAs may help decrease levels of creatine kinase, lactate dehydrogenase and granulocyte elastase which indicate reduced levels of muscle damage. In addition, consumption of BCAAs may help alter levels of testosterone and cortisol to provide a greater anabolic environment.

BCAAs & Exercise Performance

While some of the previous experiments showed that exercise performance was not affected with BCAA supplementation, they did not examine performance straight after supplementation or long term supplementation on performance.

  • Greer et al (2011)9 examined 9 untrained males and found that those consuming 25.4g of BCAAs had lower ratings of perceived exertion and performed better in cycling time trials than those who had a placebo. Although the differences in distance covered between those who consumed BCAAs over placebo was not significant, there was still a definite increase in distance travelled.
  • Tatpati et al (2010)10 conducted research on differing performance benefits of BCAAs on the young and elderly. After an infusion of BCAAs for 8 hours, the mitochondrial ATP production rate was seen to have increased in the young, but had no significant changes in the elderly. What this suggests is that an abundant supply of BCAAs could promote faster and more efficient energy production, which may be extremely beneficial for exercise performance.
  • Portier et al (2008)11 found that subjective feelings of fatigue and short term memory performance fared better with BCAA supplementation in offshore sailing than those who took a placebo. However, overall performance was not significantly affected.
  • Other studies including Schena et al (1992)12 and Candeloro et al (1995)13 found less decreases in strength with BCAA supplementation over placebo groups. This was most likely due to improvements in body composition and conservation of skeletal muscle.

Summary: Supplementation with BCAAs may help with exercise performance through lowered ratings of perceived exertion, lowered feelings of fatigue, faster and more efficient energy production as well as conservation of and possibly promotion of skeletal muscle growth. This conservation of skeletal muscle brings me to one of the most important aspects of BCAAs – leucine.

Leucine – The Star BCAA

If leucine was in Hollywood, it would be a rising star. Over the last decade or so, it has carved its way up the amino acid ladder and has become one of the most researched and most prominent of the amino acids out there.

  • Leucine is suggested as being the only amino acid capable of inducing muscle protein synthesis as a standalone nutrient. Combined with one of its metabolites; B-Hydroxy B-methylbutyrate (more commonly known as HMB), they are both considered as having anabolic and anti-catabolic properties.
  • One of the most celebrated studies showing the benefits of leucine has been Koopman et al (2005)14. This study showed that ingestion of carbohydrate, protein and leucine resulted in less protein breakdown, greater protein synthesis and overall greater whole body net protein balance than carbohydrate with protein and carbohydrate alone.
  • Another study by Ispoglou (2011)15 was able to show that 4g/day of L-leucine supplementation was able to promote an additional 9% in strength gains than those not on L-leucine supplementation.
  • Finally Crowe et al (2006)16 investigated 13 canoeists and found that 6 weeks of leucine supplementation at 45mg/kg of body weight per day led to greater plasma leucine and total BCAA concentrations, increased upper body power and decreased subjective feelings of exertion than those taking the placebo.
  • While the research is still in its beginning stages, there has been some strong evidence in animal studies showing that leucine alone has been able to affect muscle protein synthesis, which in turn has follow on effects on performance. The mechanism by which leucine is proposed to promote muscle protein synthesis is through the mammalian target of rapamycin (mTOR) signalling pathway which when activated will allow for protein synthesis.17
  • There have been some newer articles showing a lack of effect of additional leucine on muscle protein synthesis with adequate protein18 , but it is still too early to provide any overall conclusions. Leucine definitely can affect protein synthesis so the inclusion of leucine in a supplementation regime is definitely important. New research on leucine has also implicated its ability to help with diabetes in animal studies.

BCAA Ratios

There has always been considerations of BCAA supplements on the perfect ratio of leucine to isoleucine to valine. Previously the most common ratio was 2:1:1 of leucine to the other BCAAs as it is closest to animal protein ratios of BCAAs. However, with such renewed interest in leucine over the past couple of years, many supplement companies have invested in supplements with 4:1:1 and even 8:1:1 ratios. It has been shown however that substantial increases in leucine can lead to imbalances in ratios in the body of valine and isoleucine1, which could potentially have undue effects, however this is still up to the jury. One study has shown that muscle protein synthesis can be almost maximally stimulated with around 3g of leucine or 0.05g/kg of body weight19. A BCAA complex supplement providing you with at least 3g of leucine is adequate in terms of this study. However, more leucine may be required in post-exercise instances, as BCAA and especially leucine levels will most likely be depleted.

BCAA vs Protein Powder

With such a good rap for BCAAs and leucine in particular, is there a reason why you should be taking regular protein powder along with BCAAs? Or should you just take one or the other?

  • If you were considering taking BCAAs alone or even leucine alone, it could put you at risk of low intake of the other essential and non essential amino acids, many of which have been shown to have possible ergogenic effects including arginine and glutamine. There has also been evidence in animal studies showing that in order to sustain the muscle protein synthetic abilities of leucine, there needs to be other amino acids present.20
  • As protein powder fractions have BCAAs in them, one might think that consumption of whey is adequate in providing you with the BCAAs that you need for muscle protein synthesis. While this is essentially true, there is often the issue of timing.
  • While whey protein is relatively fast digesting, especially in a hydrolysed form, an addition of BCAAs may be beneficial in promoting further gains due to its ability to be quickly absorbed into the bloodstream to be incorporated into muscle to be catabolised or used as fuel leaving more muscle protein untouched. Most of the other amino acids will be catabolised in the liver.
  • There have even been studies which have looked at this phenomenon and showed that there were greater muscle mass gains with whey protein & BCAAs and glutamine than just whey protein alone.21 So while taking a protein powder with your workouts is crucial, there may be some additional benefits with taking protein with BCAAs.

Benefits of BCAAs

BCAAs are an extremely interesting set of amino acids which have been implicated for its ergogenic properties and also in the treatment of several medical conditions especially of the liver as well as diabetes. Here is a quick summary of what BCAAs can possibly do for you:

  • BCAAs may help you improve your speed of recovery and decrease levels of muscle soreness and damage.
  • BCAAs may have anti-catabolic effects and be able to alter hormone levels for an anabolic environment.
  • BCAAs may be able to help with exercise performance through changes in body composition and preservation of muscle mass.
  • Leucine, one of the BCAAs is possibly the only amino acid capable of promoting muscle protein synthesis through its ability to affect molecular signalling.
  • If consuming BCAAs, ensure that you get at least 3g of leucine with each serving or at least 0.5mg/kg body weight/serve. More may be required when exercising.
  • There is no substantial evidence to suggest added benefits of increased ratios of leucine.
  • Taking BCAAs with protein may have additional ergogenic benefits.
  • There is no toxicity of BCAAs, but a general recommendation is between 6-20g with up to 50g having been used in experiments showing positive effects.

1 Shimomura Y et al. ‘Exercise Promotes BCAA Catabolism: Effects of BCAA Supplementation on Skeletal Muscle during Exercise.’ J. Nutr. June 1, 2004 vol. 134 no. 6 1583S-1587S
Matsumoto K, Koba T, Hamada K, Sakurai M, Higuchi T, Miyata H. ‘Branched-chain amino acid supplementation attenuates muscle soreness, muscle damage and inflammation during an intensive training program.’ J Sports Med Phys Fitness. 2009 Dec;49(4):424-31.
Shimomura Y, Inaguma A, Watanabe S, Yamamoto Y, Muramatsu Y, Bajotto G, Sato J, Shimomura N, Kobayashi H, Mawatari K. ‘Branched-chain amino acid supplementation before squat exercise and delayed-onset muscle soreness.’ Int J Sport Nutr Exerc Metab. 2010 Jun;20(3):236-44.
Jackman SR, Witard OC, Jeukendrup AE, Tipton KD. ‘Branched-chain amino acid ingestion can ameliorate soreness from eccentric exercise.’ Med Sci Sports Exerc. 2010 May;42(5):962-70.
Sharp CP, Pearson DR. ‘Amino acid supplements and recovery from high-intensity resistance training.’ J Strength Cond Res. 2010 Apr;24(4):1125-30

6 Greer BK, Woodard JL, White JP, Arguello EM, Haymes EM. ‘Branched-chain amino acid supplementation and indicators of muscle damage after endurance exercise.’ Int J Sport Nutr Exerc Metab. 2007 Dec;17(6):595-607.
Coombes JS, McNaughton LR. ‘Effects of branched-chain amino acid supplementation on serum creatine kinase and lactate dehydrogenase after prolonged exercise.’ J Sports Med Phys Fitness. 2000 Sep;40(3):240-6.
Carli G,Bonifazi M, Lodi L et al (1992). Changes in exercise-induced hormoneresponse to branched chain amino acid administration. EuropeanJournal of Applied Physiology 64, 272-7
Greer BK, White JP, Arguello EM, Haymes EM. ‘Branched-chain amino acid supplementation lowers perceived exertion but does not affect performance in untrained males.’ J Strength Cond Res. 2011 Feb;25(2):539-44.
Tatpati LL, Irving BA, Tom A, Bigelow ML, Klaus K, Short KR, Nair KS. ‘The effect of branched chain amino acids on skeletal muscle mitochondrial function in young and elderly adults.’ J Clin Endocrinol Metab. 2010 Feb;95(2):894-902. Epub 2009 Dec 18.
Portier H, Chatard JC, Filaire E, Jaunet-Devienne MF, Robert A, Guezennec CY. ‘Effects of branched-chain amino acids supplementation on physiological and psychological performance during an offshore sailing race.’ Eur J Appl Physiol. 2008 Nov;104(5):787-94. Epub 2008 Aug 1312 Schena F, Guerrini F, Tregnaghi P, Kayser B. ‘Branched-chain amino acid supplementation during trekking at high altitude. The effects on loss of body mass, body composition, and muscle power.’ Eur J Appl Physiol Occup Physiol. 1992;65(5):394-8.
Candeloro N, Bertini I, Melchiorri G, De Lorenzo A. ‘Effects of prolonged administration of branched-chain amino acids on body composition and physical fitness.’ Minerva Endocrinol. 1995 Dec;20(4):217-23.
Koopman R, Wagenmakers AJ, Manders RJ, Zorenc AH, Senden JM, Gorselink M, Keizer HA, van Loon LJ. ‘Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects.’ Am J Physiol Endocrinol Metab. 2005 Apr;288(4):E645-53. Epub 2004 Nov 23.
Ispoglou T, King RF, Polman RC, Zanker C. ‘Daily L-leucine supplementation in novice trainees during a 12-week weight training program.’ Int J Sports Physiol Perform. 2011 Mar;6(1):38-50.
Crowe MJ, Weatherson JN, Bowden BF. ‘Effects of dietary leucine supplementation on exercise performance.’ Eur J Appl Physiol. 2006 Aug;97(6):664-72. Epub 2005 Oct 29.
Drummond MJ, Rasmussen BB. ‘Leucine-enriched nutrients and the regulation of mammalian target of rapamycin signalling and human skeletal muscle protein synthesis.’ Curr Opin Clin Nutr Metab Care. 2008 May;11(3):222-6.
Koopman R, Verdijk LB, Beelen M, Gorselink M, Kruseman AN, Wagenmakers AJ, Kuipers H, van Loon LJ. ‘Co-ingestion of leucine with protein does not further augment post-exercise muscle protein synthesis rates in elderly men.’ Br J Nutr. 2008 Mar;99(3):571-80. Epub 2007 Aug 13.
Norton LE, Layman DK. Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. J Nutr. 2006 Feb:136(2):533S-537S.
Kobayashi H, Kato H, Hirabayashi Y, Murakami H, Suzuki H. ‘Modulations of muscle protein metabolism by branched-chain amino acids in normal and muscle-atrophying rats.’ J Nutr. 2006 Jan;136(1 Suppl):234S-6S.
Colker CM et al. ‘Effects of supplemental protein on body composition and muscular strength in healthy athletic male adults.’ Current Therapeutic Research. January 2000: 61:1: 19-28

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