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A Review on Branched-Chain Amino Acids (BCAA)


What are Branched-Chain Amino Acids (BCAAs)? They are essential amino acids, namely leucine, isoleucine and valine, all having a branched molecular structure. BCAAs are considered essential because they are not produced naturally by the human body, unlike non-essential amino acids, therefore it is vital to source from diet. Like all amino acids, they are commonly found in protein-rich food such as meat, dairy products, and legumes. When you perform intense workouts, it’s crucial to rest, recuperate, and energize your body with the right nutrients, especially protein. BCAAs are building blocks your body consumes to synthesize proteins.

 

Mechanism of Action

BCAAs being the favourite among athletes, body builders and fitness enthusiasts, its main role is to support muscle development and maintenance. The combination of these three essential ketogenic amino acids makes up approximately one-third of skeletal muscle in the human body in form of protein, and roughly one-fifth of those found in your muscles1. Contrary to many other amino acids, since the enzyme BCAA amino-transferase is not found in the liver where most amino acids are enzymatically acted upon, BCAAs are metabolized only in the muscle cells. The rate-limiting enzyme of BCAA metabolism, branched-chain alpha-ketodehydrogenase, efficiently activated by working out or fasting, is also presented in the muscle. This is the reason why BCAAs are believed to play a role in energy production during exercise2.

 

Health Benefits on the Muscles

Through the activation of muscle protein synthesis in which the presence of leucine in BCAA is suggested to be the primary factor of the effect of growing muscle mass3,4. In one research, subjects who ingested a drink with 5.6 grams of BCAAs after their resistance workout had a 22% weightier increase in muscle protein synthesis compared to those who consumed a placebo drink4.

Some recent clinical studies reveal that exercise-induced muscle damage and muscle soreness may be curbed by oral consumption of BCAAs. Several studies demonstrate that BCAAs decrease protein breakdown during exercise and lower levels of creatine kinase and lactate dehydrogenase whereby both are the indicators that signal the degree of muscle damage5. Another recent study has implied that BCAA given before and following damaging resistance exercise limits indices of muscle damage and accelerates recovery in resistance-trained males6. It appears likely that BCAA provided greater bioavailability of substrate to improve protein synthesis and thereby the extent of secondary muscle damage associated with strenuous resistance exercise6.

Your muscle tissues use BCAAs during workout, causing levels of such in your blood vessels to decline. When blood levels of BCAAs is reduced, levels of the essential amino acid tryptophan in your brain increase3. In your brain, tryptophan is converted to serotonin, a brain chemical that is hypothesized to participate in the development of fatigue during exercise7. The rate-limiting step in the synthesis of serotonin is the transport of tryptophan across the blood-brain barrier. During endurance exercise, there is an uptake of tryptophan by the brain, suggesting that this may increase the synthesis and release of serotonin in the brain. Oral intake of BCAAs may diminish this uptake and also brain serotonin synthesis and release, thereby postponing and limiting exercise fatigue7. During the 60-minute exercise at a given work rate the subjects ratings of perceived exertion when they were given BCAAs were 7% lower, and their ratings of mental fatigue were 15% lower than when they were given placebo8.

 

Health Benefits on the Liver

BCAAs may enrich health in people with liver cirrhosis, a chronic disease in which the liver cannot function properly as a result of liver tissues scarring. Liver cirrhosis is a major risk factor for the development of hepatocellular carcinoma, the most common form of liver cancer, for which BCAA supplements may also be useful9,10. The effect of BCAAs supplementation could be particularly valuable in chronic hepatic injury with hyperammonemia and low concentrations of BCAAs in blood. The constructive effect of BCAA on liver regeneration and nutritional state of the body is related to their positive stimulatory effect on protein synthesis, secretion of hepatocyte growth factor, glutamine production and inhibitory effect on proteolysis11.

 

Health Benefits on the Pancreas

Leucine is the most readily oxidized BCAAs and therefore the most effective at secreting insulin from the pancreas. In pancreatic β cells, leucine acutely stimulates insulin secretion by serving as both metabolic fuel and allosteric activator of glutamate dehydrogenase to enhance glutaminolysis13. Long-term treatment of leucine has been shown to improve insulin secretory dysfunction of human diabetic islets via upregulation of certain key metabolic genes13. In vivo, leucine administration improves glycemic control in humans and rodents with type 2 diabetes13.

Isoleucine lowers elevated blood sugar levels by making muscle tissues to take in more sugar from your blood. The isoleucine effect on glucose uptake was mediated by phosphatidylinositol 3-kinase (PI3K)14. These results suggest that isoleucine stimulates the insulin-independent glucose uptake in skeletal muscle cells, which may contribute to the plasma glucose-lowering effect14.

 

Bonus: Pea Protein Isolate

BCAA supplements alone if not taken with a complete protein such as pea protein isolate with an adequate essential amino acids content may not adequately stimulate the synthesis of muscle protein4,12. Whether you’re taking BCAA supplement for muscle gain or reducing muscle soreness and fatigue, it is recommended to take BCAA before and after your exercises or workout, paired with pea protein isolate for maximum results.

 

Reference:

  1. Riazi R, Wykes LJ, Ball RO, Pencharz PB. The total branched-chain amino acid requirement in young healthy adult men determined by indicator amino acid oxidation by use of L-[1-13C] phenylalanine. J Nutr. 2003 May;133(5):1383-9.
  2. Shimomura Y, Yamamoto Y, Bajotto G, Sato J, Murakami T, Shimomura N, Kobayashi H, Mawatari K. Nutraceutical effects of branched-chain amino acids on skeletal muscle. J Nutr. 2006 Feb;136(2):529S-532S.
  3. Shimomura Y, Murakami T, Nakai N, Nagasaki M, Harris RA. Exercise promotes BCAA catabolism: effects of BCAA supplementation on skeletal muscle during exercise. J Nutr. 2004;134(6 Suppl):1583S-1587S.
  4. Jackman SR, Witard OC, Philp A, Wallis GA, Baar K, Tipton KD. Branched-chain amino acid ingestion stimulates muscle myofibrillar protein synthesis following resistance exercise in humans. Frontiers in Physiology. 2017;8.
  5. Coombes JS, Macnaughton 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.
  6. Howatson G, Hoad M, Goodall S, Tallent J, Bell PG, French DN. Exercise-induced muscle damage is reduced in resistance-trained males by branched chain amino acids: a randomized, double-blind, placebo controlled study. Journal of the International Society of Sports Nutrition. 2012;9(20)
  7. Newsholme EA, Blomstrand E. Branched-chain amino acids and central fatigue. J Nutr. 2006 Jan;136(1 Suppl):274S-6S.
  8. Blomstrand E, Hassmen P, Ek S, Ekblom B, Newsholme EA. Influence of ingesting a solution of branched-chain amino acids on perceived exertion during exercise. Acta Physiol Scand. 1997 Jan;159(1):41-9.
  9. Moriwaki H, Shiraki M,Fukushima H, Shimizu M, Iwasa J, Naiki T, Nagaki M. Long-term outcome of branched-chain amino acid treatment in patients with liver cirrhosis. Hepatol Res. 2008 Nov;38 Suppl 1:S102-6.
  10. Muto Y, Sato S, Watanabe A, Moriwaki H, Suzuki K, Kato A, Kato M, Nakamura T, Higuchi K, Nishiguchi S, Kumada H, Ohashi Y. Long-term Survival Study Group. Overweight and obesity increase the risk for liver cancer in patients with liver cirrhosis and long-term oral supplementation with branched-chain amino acid granules inhibits liver carcinogenesis in heavier patients with liver cirrhosis. Hepatol Res. 2006 Jul;35(3):204-14.
  11. Holecek M. Three targets of branched-chain amino acid supplementation in the treatment of liver disease. Nutrition 2010, 26, 482-490.
  12. Witard OC, Jackman SR, Breen L, Smith K, Selby A, Tipton KD. Myofibrillar muscle protein synthesis rates subsequent to a meal in response to increasing doses of whey protein at rest and after resistance exercise. Am J Clin Nutr. 2014 Jan;99(1):86-95.
  13. Yang J, Chi Y, Burkhardt BR, Guan Y, Wolf BA. Leucine metabolism in regulation of insulin secretion from pancreatic beta cells. Nutr Rev. 2010 May; 68(5): 270–279.
  14. Doi M, Yamaoka I, Fukunaga T, Nakayama M. Isoleucine, a potent plasma glucose-lowering amino acid, stimulates glucose uptake in C2C12 myotubes. Biochem Biophys Res Commun. 2003 Dec 26;312(4):1111-7.