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.
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.
Why do athletes use it?*
Some athletes say that branched-chain amino acids
helps improve strength training results.
helps improve endurance.
What do the advocates say?*
A good deal of research has been done on branched-chain amino acids (BCAAs) in athletes,
but results are quite mixed. BCAAs do not seem to enhance training benefits or exercise
performance in most situations. Some athletes, however, may experience increased mental
clarity during exercise or may be less susceptible to infections caused by the stress of
exercise. Performance under extreme conditions, such as high altitude or heat, may also be
improved with BCAAs.
How much is usually taken by athletes?
Some research has shown that supplemental BCAAs (typically 10 to 20 grams per day) do not
result in meaningful changes in body composition,1 nor do they improve exercise
performance or enhance the effects of physical training.234567 However, BCAA supplementation may be useful in special
situations, such as preventing muscle loss at high altitudes and prolonging endurance
performance in the heat.89 One controlled study gave triathletes 6
grams per day of BCAA for one month before a competition, then 3 grams per day from the day of
competition until a week following. Compared with a placebo, BCAAs restored depleted glutamine
stores and immune factors that occur in elite athletes, and led to a reported one-third fewer
symptoms of infection during the period of supplementation.10 Studies by one group
of researchers suggest that BCAA supplementation may also improve exercise-induced declines in
some aspects of mental functioning.111213
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.14 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.
*Athletes and fitness advocates may claim benefits for branched-chain
amino acids based on their personal or professional experience. These are individual opinions
and testimonials that may or may not be supported by controlled clinical studies or published
scientific articles on branched-chain amino acids. For more complete and detailed information,
including references and safety information, see
Branched-Chain Amino Acids as nutritional supplements.
References (To view, roll mouse over the "References" heading; to hide, click on the heading)
1. Kelly GS. Sports nutrition: A review of selected nutritional
supplements for bodybuilders and strength athletes. Alt Med Rev
1997;2:184–201.
2. 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].
3. 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.
4. 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.
5. Davis JM, Welsh RS, De Volve KL, et al. Effects of branched-chain
amino acids and carbohydrate on fatigue during intermittent, high Intensity running. Int J
Sports Med 1999;20:309–14.
6. 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.
7. 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.
8. 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.
9. 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.
10. Bassit RA, Sawada LA, Bacurau RF, et al. The effect of BCAA
supplementation upon the immune response of triathletes. Med Sci Sports Exerc
2000;32:1214–9.
11. Hassmén P, Blomstrand E, Ekblom B, Newsholme EA. Branched-chain
amino acid supplementation during 30-km competitive run: mood and cognitive performance.
Nutrition 1994;10:405–10.
12. 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.
13. 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.
14. 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.
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 pharmacist for any health problem and before using any supplements or
before making any changes in prescribed medications. Information expires June 2009.
