Odds are good that if you take your fitness performance seriously, you have either used branched-chain
aminos acid (BCAA) supplements or at least heard of them. Now more than ever, those gym goer’s with their
gallon jug of neon colored liquid are most likely BCAA’s.
However, the science in recent years has shown that BCAA’s aren’t nearly as useful for fitness performance,
with their counterpart essential amino acid (EAA) supplements becoming more and more prevalent in fitness
supplements. So what are the differences between the two and when should you use one, or the other, or
What’s an amino acid?
Let’s start with amino acids in general. There are twenty amino acids in existence, each of which can be
thought of as a building block of protein. Amino acids can be linked together within your cells to create
peptides, which then can interact and
fold upon themselves to create the
proteins we fitness enthusiasts have
learned to love. When we consume
protein, it is broken down into amino
acids that our cells then take up and use
to create their own proteins. This is why
amino acids can be useful during exercise,
as they are absorbed much quicker than
proteins, due to the decreased need for digestion/processing. Of the twenty amino acids, nine of them are
considered essential, meaning that your body lacks the ability to create them on their own and must be
ingested via diet or supplementation. The other 11 are deemed non-essential, meaning your body can indeed
synthesize them on its own if required.
BCAA vs. EAA, What’s the
Out of the twenty amino acids,
three of them contain “branches”
protruding out from their molecular
structure; making their title of
BRANCH chained amino acids quite
fitting. These three are leucine,
isoleucine, and valine; all of which belong to the EAA category. In humans, BCAA’s represent roughly 35% of
the amino acids within skeletal muscle tissue (the type of muscle you train when working out). During
exercise, these amino acids are oxidized (depleted) within muscles, and overtime can result in muscle loss  .
Knowing this, it makes sense why BCAA supplementation has been shown to retain muscle loss in
malnourished populations, such as the elderly and those with diseases such as cancer [2-4] . Thus, it can be
easily understood why BCAA’s have been pushed so heavily to both retain muscle during a cutting phase or
building muscle in a bulking phase.
While all three BCAA’s are essential, there still are the additional six that are absolutely necessary in your
diet for survival and proper bodily function. Animal meats, eggs, beans, and nuts are fantastic sources of
various EAA’s; and virtually all foods that contain protein, whether plant or animal-based, will contain at least
some of the EAA’s. While most EAA supplements do contain a higher BCAA:EAA ratio, they still include
sufficient levels of the other 6 EAA’s.
Why EAA’s reign supreme
To keep it brief: I personally feel that EAA’s are superior to BCAA’s in virtually any instance!
The main reason why I suggest EAA’s over BCAA’s is the fact that a recent paper used very thorough
scientific methods to demonstrate that contrary to what the scientific community has said in the past; not
only oral, but even intravenous BCAA supplementation does NOT increase muscle protein synthesis in a living
organism  . Simply put, your body requires all EAA’s must be present within a cell to significantly increase
the rate of protein synthesis. While leucine has been shown to stimulate the mTOR cellular pathway (which is
the main signaling pathway for muscle growth) and induce muscle protein synthesis [6, 7] , a complete EAA
profile must be present in order for the mTOR signaling to actually lead to the production of new contractile
muscle tissue. After all, who cares if your muscle cells are signaling to build more muscle if at the end of the
day no muscle growth occurs? Having EAA’s immediately post workout supplies your body with rapidly
absorbed/utilized nutrients necessary for immediate muscle protein synthesis and eventual muscle growth.
Another reason to choose EAA’s over BCAA’s are the reduced neurotransmitter levels within your brain that
has been shown to occur with BCAA supplementation. Neurons in your brain release neurotransmitters to
signal to each other; with the three major ones being serotonin, dopamine, and adrenaline. To put it simply,
these three are responsible for making your happy, motivated, and energized, respectively. Like many other
signaling molecules in your body, serotonin and dopamine/adrenaline are created from amino acids.
Serotonin is created by turning tryptophan into 5-HTP, and dopamine and adrenaline are created by turning
tyrosine into L-dopa. After ingesting foods or supplements containing these amino acids, they are absorbed
from your gut, travel through your blood, and must use transport proteins to enter your brain. These transport
proteins are specific for amino acids and can only transport one amino acid at a time. This means that the
amino acids in your blood have to compete for the available transporters to enter your brain. Knowing this, it
isn’t hard to imagine how ingesting BCAA’s would dramatically increase the amount of BCAAs in your blood,
which would mean the BCAA’s would have a higher probability to bind a transporter and enter your brain. One
study demonstrated that BCAA supplementation in rats does indeed flood transporters, resulting in less
tryptophan and tyrosine uptake into the brain, leading to decreased brain serotonin, dopamine, and
adrenaline levels  . Not only can this affect physical performance, but chronic BCAA use could also negatively
affect your overall mood due to lowered neurotransmitter levels. Supplementing with complete EAA’s
provides your body with both tryptophan and tyrosine, preventing this inhibition of uptake.
The main take home message is this; BCAA’s can be useful for MAINTAINING muscle during a cutting phase,
but NOT for building muscle. However, even if you are focused on leaning out, I would still strongly suggest
supplementing with EAA’s anyways as well to not only give your muscles everything they need to build muscle
(which CAN occur at times during a cutting phase), but also prevent your amino acid ratios from getting out of
whack, as well as get a kick start on muscle recovery after training. Lucky for you, the fitness industry has
noted these new advances in science and EAA supplements are on the rise! I personally sip on a 2:1 EAA/BCAA
blend as I drive to the gym to load my muscles to prevent any amino acid oxidation during my training, and
throughout my workouts to keep the microenvironment within my muscles as anabolic as possible.
- Shimomura, Y., et al., Exercise promotes BCAA catabolism: effects of BCAA supplementation on skeletal
muscle during exercise. J Nutr, 2004. 134(6 Suppl): p. 1583S-1587S.
- Eley, H.L., S.T. Russell, and M.J. Tisdale, Effect of branched-chain amino acids on muscle atrophy in
cancer cachexia. Biochem J, 2007. 407(1): p. 113-20.
- Louard, R.J., E.J. Barrett, and R.A. Gelfand, Effect of infused branched-chain amino acids on muscle and
whole-body amino acid metabolism in man. Clin Sci (Lond), 1990. 79(5): p. 457-66.
- Busquets, S., et al., Branched-chain amino acids inhibit proteolysis in rat skeletal muscle: mechanisms
involved. J Cell Physiol, 2000. 184(3): p. 380-4.
- Wolfe, R.R., Branched-chain amino acids and muscle protein synthesis in humans: myth or reality? J Int
Soc Sports Nutr, 2017. 14: p. 30.
- Anthony, J.C., et al., Leucine stimulates translation initiation in skeletal muscle of postabsorptive rats
via a rapamycin-sensitive pathway. J Nutr, 2000. 130(10): p. 2413-9.
- Anthony, J.C., et al., Orally administered leucine stimulates protein synthesis in skeletal muscle of
postabsorptive rats in association with increased eIF4F formation. J Nutr, 2000. 130(2): p. 139-45.
- Choi, S., et al., Oral branched-chain amino acid supplements that reduce brain serotonin during exercise
in rats also lower brain catecholamines. Amino acids, 2013. 45(5): p. 1133-1142.