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Branched Chain Amino Acids (BCAAs) – All you need to know

Dr. Meenakshi Noll | December 1, 2015 | Sports Medicine, Supplements

WHAT ARE BRANCHED CHAIN AMINO ACIDS?

BCAA stands for Branched Chain Amino Acids because of their chemical structure or formula. Each amino acid (as the name shows) has an amino group (NH2) and an acid group (COOH), and rest in between is a chain of groups like ––CH2 defines the name and function of the particular amino acid. Of all the amino acids (there are 22 in total), only 3 are called Branched Chain Amino Acids, namely Valine, Leucine and Isoleucine. These three amino acids have a branched chain rather than a linear chain thus the name.

WHAT BENEFITS DO BCAAS PROVIDE?

Exercise leads to a depletion of liver glycogen and muscle glucose levels decrease. BCAAs are the only amino acids that are metabolized in muscle and go direct to circulation. The rest of the amino acids are metabolized in liver. BCAAs delay central fatigue and maintain glucose levels in muscle. They also delay exercise induced muscle damage and tissue breakdown. BCAAs let the athletes train harder because of their protein sparing effect.

FOR WHOM ARE BCAAS BENEFICIAL TO TAKE AND WHY?

BCAA supplementation is beneficial in relation to sports and exercise. The requirement of BCAAs is increased after exercise due to muscle degradation. Thus, athletes or even people exercising regularly would benefit from BCAA supplements. BCAA supplementation, before and after exercise promotes muscle protein synthesis and decreases exercise related muscle damage. However, the results for endurance performance with BCAA are inconsistent and are more for sprinting or weight training.

TOXICITY OF BCAAS

Numerous toxicity studies have been performed in rats and mice, however no toxicity has been reported with BCAA supplementation. There have been no reports on BCAA related toxicity in sports and exercise.

WHO SHOULD NOT TAKE IT AND WHY?

  • Pregnant and lactating women
  • Anyone who is on medication for illnesses like diabetes, high blood pressure, Parkinson’s and so on
  • Children under the age of 16yrs
OPTIMUM NUTRITION BCAA
CELLUCOR BCAA SUPPLEMENT

 

NATURA FORMULAS BCAA

 

WHAT ARE AMINO ACIDS?

Amino acids are building blocks of protein. There are 22 amino acids that are required in the body to carry out various functions especially protein synthesis. Among all amino acids, 9 are called essential amino acids as they are not produced in the body and must be obtained from external sources like animal food products (e.g. milk proteins). Out of these 9 essential amino acids, three are called branched chain amino acids (BCAAs), named as such because of their chemical formulae, these three are: Leucine (Leu), Isoleucine (Isoleu) and valine (Val).

Of the three BCAAs, isoleucine and Valine are glucogenic (make precursors to synthesize glucose) and leucine is ketogenic (makes precursors for ketone bodies and fatty acid synthesis)1. BCAAs make up for about one-third of muscle protein2. They are involved in protein synthesis and energy production3, thus BCAAs (especially leucine) have important function in various metabolic processes like muscle formation and repair 2. It has been shown that adding leucine (76%) to a high protein supplement leads to reduction of visceral fat, high-level performance, repairing and building of muscle tissue4.

WHY BCAAS ARE IMPORTANT

All amino acids other than BCAAs are broken down by liver and then transported to other parts of the body. However, BCAAs are metabolized by muscle and muscle is not a gluconeogenic organ meaning it cannot synthesize glucose. Therefore, valine and isoleucine cannot be converted to glucose in muscle5, rather leucine is the only BCAA that can recycle glucose in muscle6.

 

Fig 17: shows leucine gets converted to alanine in the skeletal muscle. Alanine then reaches liver where it is converted again to glucose. This is calledglucose alanine cycle. However, in low energy state, leucine augments glucose stimulation via getting converted to glutamate, which is then converted to alanine and thus re-synthesizes glucose. This mechanism keeps a stable glucose supply when there is low insulin and less available energy8,9. At the same time, leucine can stimulate insulin secretion and protein synthesis when enough energy is available. This insulin then enters the glutamate pathway thus modulating the glucose metabolism. Thus, leucine is the only BCAA that can control glucose metabolism via both insulin and non-insulin pathways10. At the same time, BCAAs are all unique as they are metabolized in muscle where they can be broken down when energy is needed quickly.

WHY WE FEEL TIRED WITH EXERCISE

There are two main factors behind fatigue during physical exercise:

Peripheral and Central factors.

Both of these are affected by the nutrition, intensity and time of exercise, and the training status of the person.

Peripheral fatigue: There have been numerous studies on this aspect of fatigue. Some causes described are depletion of phosphocreatine in muscle, reduction of muscle glycogen, failure of neuromuscular transmission and even buildup of protons11.

Central fatigue: Two main reasons have been described for central fatigue.

  • There is depletion of liver glycogen during prolonged exercise leading to a decrease in blood glucose levels
  • The other factor is increase in the ratio of concentration of free tryptophan / BCAA, uptake of tryptophan (an amino acid) by the brain and increase in the release of neurotransmitter 5-HT (5 hydroxy tryptamine)12, 12b during sustained exercise. In other words, BCAAs are taken up by muscle and their concentration in plasma becomes less.

HOW BCAAS HELP POSTPONE FATIGUE

As explained above the ratio of free tryptophan/BCAA increases during exercise, therefore, if BCAAs are consumed, then their levels in plasma will increase, which in turn reduces the free tryptophan/BCAA ratio. This in turn decreases the 5-HT synthesis in brain delaying the central fatigue. In addition, BCAAs maintain glucose levels in the muscle (Fig 1), therefore, it’s important to take a carbohydrate or protein drink during or after training to increase the insulin levels and thus transport of BCAAs in cells. However as explained above, leucine is the lead player in protein synthesis, thus building muscle. Therefore, it is inadvisable to train or exercise during fasting or not eating afterwards, as that will only lead to muscle loss. Leucine supplementation has been shown to even aid in the recovery of regenerating Tibialis Anterior Muscle (TA) when analyzed on day 10 post injury13.

There has been quite a bit of literature lately on BCAAs and their use in sports and resistance training. BCAAs have been shown to reduce the exercise induced muscle damage. There have been conflicting reports on when these amino acids should be used. However, taking them both before and after the resistance training has shown an improvement in protein synthesis and thus prevent the muscle damage14. It has also been reported that the use of BCAAs taken together with carbohydrates, shows improvement in mental agility during sustained competitive exercises15. In addition, BCAAs have been found to decrease the serum levels of creatine phosphokinase (CPK) and lactate dehydrogenase (LDH)16 , which are indicators of muscle damage and tissue breakdown. This shows that BCAAs lower the exercise induced muscle damage in the body. Literature also shows that BCAAs exert a protein sparing17 effect that allows the athletes to train harder during training cycles. This allows for greater recovery time by decreasing the exercise-induced damage18. Recent studies have also shown involvement of BCAAs in improving skeletal muscle wasting even if not caused by training19.

HOW MUCH BCAAS TO TAKE

An upper limit of 450 mg/Kg body mass/day is well tolerated20 and is not advisable to increase this limit as it would stress the kidneys and could lead to deleterious effects. Similarly, an upper limit of leucine has been reported as 500mg/Kg body wt/day or an approximation of about 35g/day is a cautious estimate21. For individual use, people will have to start from 5g/day and see the results.

REFERENCES:

  1. Harper, A. E.; Miller, R. H. a.; Block, K. P., Branched-chain amino acid metabolism. Annu Rev Nutr 1984, 4, 409-454.
  2. Mero, A., Leucine supplementation and intensive training. Sports Med. 1999, 27, 347-358.
  3. Anthony, J. C. e. a., Signaling pathways involved in translational control of protein synthesis in skeletal muscle by leucine. J. Nutr. Biochem. 2001, 131, 856S-860S.
  4. Freudenberg, A.; Klaus, S., Comparison of high-protein diets and leucine supplementation in the prevention of metabolic syndrome and related disorders in mice. . J. Nutr. Biochem. 2012, 23 (11), 1524-30.
  5. Wagenmakers, A. J., Muscle amino acid metabolism at rest and during exercise: role in human physiology and metabolism. Exerc. Sport. Sci. Rev. 1998, 26, 287-314.
  6. Layman, D. K.; Walker, D. A., Potential importance of leucine in treatment of obesity and the metabolic syndrome. J Nutr 2006, 136, 319S-323S.
  7. Campos-Ferraz, P. L.; Bozza, T.; Nicastro, H. a.; Lancha, A. H., Distinct effects of leucine or a mixture of the branched-chain amino acids (leucine, isoleucine, and valine) supplementation on resistance to fatigue, and muscle and liver-glycogen degradation, in trained rats. 2013, 29, 1388-1394.
  8. Layman, D. K., The role of leucine in weight loss diets and glucose homeostasis. J Nutr 2003, 133, 261S-267S.
  9. Nicastro, H.; Zanchi, N. E.; da Luz, C. R. a.; de Moraes, W. M., Effects of leucine supplementation and resistance exercise on dexamethasone-induced muscle atrophy and insulin resistance in rats. Nutrition 2012, 28, 465-471.
  10. Nicastro, H.; da Luz, C. R.; Chaves, D. F.; Bechara, L. R.; et.al., Does branched-chain amino acids supplementation modulate skeletal muscle remodeling through inflammation modulation? Possible mechanisms of action. J. Nutr. Biochem. 2012, 136937.
  11. Astrand, P. O.; Rodahl, K.; Dahl, H. A.; Sromme, S. B., Textbook of work physiology. 4th ed.; Human Kinetics: Champain, IL, 2003.
  12. (a) Newsholme, E. A.; Acworth, I. N., Amino acids, brain neuro- transmitters and a functional link between muscle and brain that is important in sustained exercise. In Advances in myochemistry., G, B., Ed. John Libbey: London, 1987; pp 127-
  13. (b) Blomstran, E.; Celsing, F.; Newsholme, E. A., Changes in plasma concen- trations of aromatic and branched-chain amino acids during sustained exercise in man and their possible role in fatigue. . Acta Physiol Scand 1988, 133, 115-121.
  14. Pereira, M. G.; Silva, M. T.; Carlassara, E. O. C.; et.al., Leucine Supplementation Accelerates Connective Tissue Repair of Injured Tibialis Anterior Muscle. Nutritents 2014, 6, 3981-4001.
  15. Howatson, G.; Hoad, M.; Goodall, S.; Tallent, J.; Bell, P. G.; French, D. N., Exercise induced muscle damage is reduced in resistance trained males by branched chain amino acids: a randomized, double-blind, placebo controlled study. J Int Soc Sports Nutr 2012, 9, 20.
  16. Hassmen, P.; Blomstran, E.; Ekbolom, B., and; Newsholme, E. A., Branched-chain amino acid supplementation during 30-km competitive run: mood and cognitive performance. . Nutrition 1994, 10, 405-410.
  17. MacLean, D. A.; Graham, T. E. a.; Saltin, B., Branched-chain amino acids augment ammonia metabolism while attenuating protein breakdown during exercise. The American Journal of Physiology 1994, 6, 1.
  18. Norton, L. E. a.; Layman, D. K., Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. The Journal of Nutrition 2006, 136, 2.
  19. Kim, D. H.; Kim, S. H.; Jeong, W. S. a.; Lee, H. Y., Effect of BCAA intake during endurance exercises on fatigue substances, muscle damage substances, and energy metabolism substances. J. Exerc. Nutr. Biochem 2013, 17 (4), 169-180.
  20. Tomoda, K.; Kubo, K.; Hino, K.; Kondoh, Y.; et.al., Branched-chain amino acid-rich diet improves skeletal muscle wasting caused by cigarette smoke in rats. J. Toxicol. Sci. 2014, 39 (2), 331-337.
  21. Gleeson, M., Interrelationship between Physical Activity and Branched-Chain Amino Acids. J. Nutr. 2005, 135, 1591S-1595S.
  22. Elango, R., Chapman, K., Rafii, M, Ball, R.O. and Pencharz, P.B., Determination of the tolerable upper intake level of leucine in acute dietary studies in young men. Am J Clin Nutr 2012, 96, 759-767.

By Dr. Meenakshi Noll