Branched-Chain Amino Acids
Also indexed as: BCAAs, Isoleucine, Leucine, Valine
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):
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
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.
1. Zello GA, Wykes LF, Ball RO, et al. Recent advances in methods of
assessing dietary amino acid requirements for adult humans. J Nutr
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.