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Branched-Chain Amino Acids

Also indexed as: BCAAs, Isoleucine, Leucine, Valine

Illustration

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.

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

Science Ratings Health Concerns
2Stars

Kidney failure (intravenous BCAAs)

Liver cirrhosis

Phenylketonuria

1Star

Athletic performance (for high altitude and extreme temperature only)

Hepatic encephalopathy

Spinocerebellar degeneration

Tardive dyskinesia

3Stars 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 an 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.1 2 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.3 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:

1. 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.

2. 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.

3. 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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