Branched-Chain Amino Acids

Also indexed as: BCAAs, Isoleucine, Leucine, Valine

What are they?

The branched-chain amino acids (BCAAs) are leucine, isoleucine, and valine. BCAAs are considered essential amino acids because human beings cannot survive unless these amino acids are present in the diet.

BCAAs are needed for the maintenance of muscle tissue and appear to preserve muscle stores of glycogen (a storage form of carbohydrate that can be converted into energy).¹ BCAAs also help prevent muscle protein breakdown during exercise.²

Some research has shown that BCAA supplementation (typically 10-20 grams per day) does not result in meaningful changes in body composition,³ nor does it improve exercise performance⁴ ⁵ ⁶ ⁷ ⁸ or enhance the effects of physical training.⁹ ¹⁰ However, BCAA supplementation may be useful in special situations, such as preventing muscle loss at high altitudes¹¹ and prolonging endurance performance in the heat.¹² Studies by one group of researchers suggest that BCAA supplementation may also improve exercise-induced declines in some aspects of mental functioning.¹³ ¹⁴ ¹⁵

BCAAs can active glutamate dehydrogenase—an enzyme that is deficient in amyotrophic lateral sclerosis (ALS), also called Lou Gehrig’s disease. In one double-blind trial, 26 grams per day of BCAA supplements helped those with ALS maintain muscle strength.¹⁶ However, a larger study was ended early when people using BCAAs not only failed to improve, but experienced higher death rates than the placebo group.¹⁷ Other studies have shown no benefit of BCAA supplementation for ALS or other neuromuscular diseases,¹⁸ ¹⁹ though a small group of people suffering from diseases of the nervous system collectively called spinocerebellar degeneration did improve when given BCAAs in a preliminary study.²⁰

One study investigating the advantages of BCAA supplementation for people with diabetes undergoing an intense exercise programme found no additional benefit of BCAAs on reducing abdominal fat or improving glucose metabolism.²¹

Patients with liver diseases that lead to coma—called hepatic encephalopathy—have low concentrations of BCAAs and excess levels of certain other amino acids. Preliminary research suggested that people with this condition might be helped by BCAAs. Double-blind studies have produced somewhat inconsistent results,²² ²³ ²⁴ but a reanalysis of these studies found an overall benefit for the symptoms of encephalopathy.²⁵ Therapeutic effects of BCAAs have also been shown in children with liver failure²⁶ and adults with cirrhosis of the liver.²⁷ Any treatment of people with liver failure requires the direction of a physician.

People with chronic kidney failure may also benefit from BCAA supplementation. A preliminary study found improved breathing and sleep quality in people given intravenous BCAAs during kidney dialysis.²⁸

Phenylketonuria (PKU) is a genetic disease that causes abnormally high amounts of phenylalanine and its end products to accumulate in the blood, causing damage to the nervous system. A controlled trial demonstrated that regular use of BCAAs by adolescents and young adults with PKU, improved performance on some tests of mental functioning.²⁹ This outcome makes sense because BCAAs may compete with phenylalanine, reducing its toxic effects.

In tardive dyskinesia, phenylalanine levels have also been reported to be elevated. As a result, one group of researchers gave tardive dyskinesia patients BCAAs (from 150 mg per 2.2 pounds body weight up to 209 mg per 2.2 pounds body weight) after breakfast and one hour before lunch and dinner for two weeks.³⁰ The BCAA mixture included equal parts valine and isoleucine plus 33% more leucine than either of the other two amino acids. Of nine patients so treated, six had at least a 58% decrease in symptoms, and all people in the study had a decrease of at least 38% in symptoms.

Where are they found?

Dairy products and red meat contain the greatest amounts of BCAAs, although they are present in all protein-containing foods. Whey protein and egg protein supplements are other sources of BCAAs. BCAA supplements provide the amino acids leucine, isoleucine, and valine.

BCAAs have been used in connection with the following conditions (refer to the individual health concern for complete information):

Science Ratings

Health Concerns

Kidney failure (intravenous BCAAs)

Liver cirrhosis

Phenylketonuria

Athletic performance (for high altitude and extreme temperature only)

Hepatic encephalopathy

Spinocerebellar degeneration

Tardive dyskinesia

Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars

Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star

For a herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.

Who is likely to be deficient?

Only a person deficient in protein would become deficient in BCAAs, because most foods that are sources of protein supply BCAAs. Few people in Western societies are protein deficient.

How much is usually taken?

Most diets provide an adequate amount of BCAAs for most people, which is about 25–65 mg per 2.2 pounds of body weight.³¹ ³² Athletes involved in intense training often take 5 grams of leucine, 4 grams of valine, and 2 grams of isoleucine per day to prevent muscle loss and increase muscle gain, though most research does not support this use of BCAAs.

Are there any side effects or interactions?

Side effects have not been reported with the use of BCAAs. Until more research is conducted, people with ALS should avoid taking supplemental BCAAs. In one study, supplementation with a large amount of BCAAs (60 grams) caused alterations in the blood levels of tryptophan, phenylalanine, and tyrosine.³³ The changes in the blood levels of these amino acids could, in theory, cause depression in susceptible individuals. Until more is known, individuals with a history of depression should consult a doctor before supplementing with BCAAs. People with kidney or liver disease should not consume high amounts of amino acids without consulting their doctor.

At the time of writing, there were no well-known drug interactions with branched-chain amino acids.

References
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1. Blomstrand E, Ek S, Newsholme EA. Influence of ingesting a solution of branched-chain amino acids on plasma and muscle concentrations of amino acids during prolonged submaximal exercise. Nutrition 1996;12:485-90.

2. MacLean DA, Graham TE, Saltin B. Branched-chain amino acids augment ammonia metabolism while attenuating protein breakdown during exercise. Am J Physiol 1994;267:E1010-22.

3. Kelly GS. Sports nutrition: a review of selected nutritional supplements for bodybuilders and strength athletes. Med Rev 1997;2:184-201.

4. Van Hall G, Raaymakers JSH, Saris WHM, Wagenmakers AJM. Supplementation with branched-chain amino acids (BCAA) and tryptophan has no effect on performance during prolonged exercise. Clin Sci 1994;87:52 [abstract #75].

5. Blomstrand E, Hassmen P, Ek S, et al. Influence of ingesting a solution of branched-chain amino acids on perceived exertion during exercise. Acta Physiol Scand 1997;159:41-9.

6. Van Hall G, Raaymakers JSH, Saris WHM, Wagenmakers AJM. Supplementation with branched-chain amino acids (BCAA) and tryptophan has no effect on performance during prolonged exercise. Clin Sci 1994;87:52 [abstract #75].

7. Madsen K, MacLean DA, Kiens B, et al. Effects of glucose, glucose plus branched-chain amino acids, or placebo on bike performance over 100 km. J Appl Physiol 1996;81:2644-50.

8. Davis JM, Welsh RS, De Volve KL, Alderson NA. Effects of branched-chain amino acids and carbohydrate on fatigue during intermittent, high-intensity running. Int J Sports Med 1999;20:309-14.

9. Vukovich MD, Sharp RL, Kesl LD, et al. Effects of a low-dose amino acid supplement on adaptations to cycling training in untrained individuals. Int J Sport Nutr 1997;7:298-309.

10. Freyssenet D, Berthon P, Denis C, et al. Effect of a 6-week endurance training programme and branched-chain amino acid supplementation on histomorphometric characteristics of aged human muscle. Arch Physiol Biochem 1996;104:157-62.

11. Schena F, Guerrini F, Tregnaghi P, et al. 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 1992;65:394-8.

12. Mittleman KD, Ricci MR, Bailey SP. Branched-chain amino acids prolong exercise during heat stress in men and women. Med Sci Sports Exerc 1998;30:83-91.

13. Hassmè¬ P, Blomstrand E, Ekblom B, Newshomle EA. Branched-chain amino acid supplementation during 30-km competitive run: mood and cognitive performance. Nutrition 1994;10:405-10.

14. Blomstrand E, Hassmen P, Ek S, et al. Influence of ingesting a solution of branched-chain amino acids on perceived exertion during exercise. Acta Physiol Scand 1997;159:41-9.

15. Blomstrand E, Hassmen P, Ekblom B, et al. Administration of branched-chain amino acids during sustained exercise—effects on performance and on plasma concentration of some amino acids. Eur J Appl Physiol 1991;63:83-8.

16. Plaitakis A, Smith J, Mandeli J, et al. Pilot trial of branched-chain amino acids in amyotrophic lateral sclerosis. Lancet 1988;1:1015-8.

17. The Italian ALS Study Group. Branched-chain amino acids and amyotrophic lateral sclerosis: a treatment failure? Neurology 1993;43:2466-70.

18. Tandan R, Bromberg MB, Forshew D, et al. A controlled trial of amino acid therapy in amyotrophic lateral sclerosis: I. Clinical, functional, and maximum isometric torque data. Neurology 1996;47:1220-6.

19. MacLean D, Vissing J, Vissing SF, Haller RG. Oral branched-chain amino acids do not improve exercise capacity in McArdle disease. Neurology 1998;51:1456-9.

20. Mori N, Adachi Y, Takeshima T, et al. Branched-chain amino acid therapy for spinocerebellar degeneration: a pilot clinical crossover trial. Intern Med 1999;38:401-6.

21. Mourier A, Gautier JF, De Kerviler E, et al. Mobilization of visceral adipose tissue related to the improvement in insulin sensitivity in response to physical training in NIDDM. Effects of branched-chain amino acid supplements. Diabetes Care 1997;20:385-91.

22. Maddrey WC. Branched chain amino acid therapy in liver disease. J Am Coll Nutr 1985;4:639-50 [review].

23. Wahren J, Denis J, Desurmont P, et al. Is intravenous administration of branched chain amino acids effective in the treatment of hepatic encephalopathy? A multicenter study. Hepatology 1983;3:475-80.

24. Egberts E-H, Schomerus H, Hamster W, Jï¿½ P. Branched chain amino acids in the treatment of latent portosystemic encephalopathy. Gastroenterology 1985;88:887-95.

25. Naylor CD, O’Rourke K, Detsky AS, et al. Parenteral nutrition with branched-chain amino acids in hepatic encephalopathy. A meta-analysis. Gastroenterology 1989;97:1033-42.

26. Chin SE, Sheperd RW, Thomas BJ, et al. Nutritional support in children with end-stage liver disease: a randomized crossover trial of a branched-chain amino acid supplement. Am J Clin Nutr 1992;56:158-63.

27. Kato M, Miwa Y, Tajika M, et al. Preferential use of branched-chain amino acids as an energy substrate in patients with liver cirrhosis. Intern Med 1998;37:429-34.

28. Soreide E, Skeie B, Kirvela O, et al. Branched-chain amino acid in chronic renal failure patients: respiratory and sleep effects. Kidney Int 1991;40:539-43.

29. Berry HK, Brunner RL, Hunt MM, et al. Valine, isoleucine, and leucine. A new treatment for phenylketonuria. Am J Dis Child 1990;144:539-43.

30. Richardson MA, Bevans ML, Weber JB, et al. Branched chain amino acids decrease tardive dyskinesia symptoms. Psychopharmacology 1999;143:358-64.

31. Zello GA, Wykes LF, Ball RO, et al. Recent advances in methods of assessing dietary amino acid requirements for adult humans. J Nutr 1995;125:2907–15.

32. Young VR, Bier DM, Pellett PL. A theoretical basis for increasing current estimates of the amino acid requirements in adult man, with experimental support. Am J Clin Nutr 1989;50:80–92.

33. Scarna A, Gijsman HJ, Harmer CJ, et al. Effect of branch chain amino acids supplemented with tryptophan on tyrosine availability and plasma prolactin. Psychopharmacology 2002;159:222–3.

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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or chemist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires March 2007.

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