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Anabolic Effects of Branched-Chain Amino Acids

Bane in the DC Comics series is the only super-villain to have broken Batman's back in a fight. Bane

became a test subject for a mysterious drug known as "Venom," which had killed the other test

subjects and he was the only one who survived. Bane found the drug caused him to have superhuman

strength, although he needed to take it via a system of cables pumped directly into his muscles. In the

comics, the drug Venom was a mixture of radioactive steroids, growth hormone and amino acids for

muscle growth. Although radioactive steroids may be science fiction, the anabolic effects of amino acid

are not.

There's little doubt that efficient recovery of protein metabolism is critical to the anabolic process and

preservation of skeletal muscle hypertrophy. Amino acid supplementation has been demonstrated to

heighten recovery during weight training by increasing protein synthesis, reducing muscle protein

breakdown and reducing muscle damage.

Free amino acids in humans are classified as essential amino acids and non-essential. Essential amino

acids need to be obtained from the diet, whereas non-essential amino acids are endogenous (produced

by the body). In terms of muscle protein synthesis, only the essential amino acids are needed. For

example, after an intense resistance exercise program, where subjects are administered either a

mixture of non-essential or essential amino acids alone, only essential amino acids increased protein

insulin, growth hormone and IGF-1- and may even enhance testosterone production.

Amino Acids, Training & Testosterone

prevented strength loss during an intense overreaching program. Overreaching is an accumulation of

training stress, resulting in a short-term decrement in performance capacity followed by a supercompensation

effect. In that study, 17 resistance-trained men were randomly assigned to either an

essential amino acid group or placebo group before embarking on a five-week overtraining program.

Each participant ingested the amino acid supplement separate from meals (i.e., one hour before a meal

and two hours after a meal).

In relation to the exercise bout, supplement doses were taken one to two hours pre- and post-exercise.

and evening dose. After one week of overreaching, 1 RM on the bench press had decreased in the

placebo group, but not the essential amino acid group. Both groups then showed similar increases in

The study indicates that amino acid supplementation is effective in preventing the initial strength loss

seen when first starting a high-volume program, probably by creating an anabolic environment and

reducing muscle damage. It's also been demonstrated that ingestion or infusion of essential amino

studies have reported that when whey protein or essential amino acids are matched for their effects on

net muscle protein synthesis, both supplements stimulated protein synthesis rates, but the increase

amino acids (15 grams of essential amino acids and 30 grams of sucrose) between whole meals

produces a greater anabolic effect than ingestion of a liquid meal replacement (23 grams protein, 126

Amino Acids, Resistance Exercise & Protein Synthesis

High-protein intakes increase the retention of nitrogen and place weight trainers in a more anabolic

environment. For example, Tarnopolsky and colleagues found that when strength lifters were

administered 0.8, 1.4 and 2.4 grams of protein per kilogram of bodyweight, nitrogen balance was

Protein is broken down into amino acids. Gym rats know that you need protein and sufficient calories to

increase muscle mass, but new research suggests that the timing of amino acid intake is essential for

this increase. For years, fitness enthusiasts were told that there was a heightened 45-minute "window

of opportunity" after exercise in which anabolic reactions take place. So, why is it so important to get

essential amino acids into your system quickly after exercise? One reason is that heavy, intense

exercise stimulates cortisol production, which results in increases in muscle-protein breakdown.

Researchers wanted to know what happened when you infused subjects with cortisol and the effects

essential amino acids have on cortisol. Administration of essential amino acids not only increased

After resistance exercise, increased protein synthesis has been documented for up to 48 hours

opportunity" theory. Studies have reported that a delay in protein consumption after exercise may

delay protein synthesis rates. For example, after intense leg exercise, subjects were fed an oral nutrient

supplement (10 grams protein, 8 grams carbohydrate and 3 grams fat), which was administered either

immediately after exercise or three hours after exercise.

Researchers found that the net uptake of amino acids and glucose immediately after exercise led to

more substrate and energy availability within the leg for protein synthesis. Although leg protein

breakdown wasn't significantly different between the two supplementations, leg protein synthesis

increased more than threefold when a protein supplement was consumed immediately after exercise

For an even greater effect, researchers discovered that using an amino acid/carbohydrate beverage

seems that in order to receive the optimal effects of protein supplementation, the "window of

opportunity" theory should be changed to consuming protein supplements or amino acid supplements

synthesis to exercise is a result of the metabolic changes induced by the muscular concentration and

the availability of amino acids. Although many Arnold wannabes are still using protein supplements,

remember that only essential amino acids are needed for increasing protein synthesis rates. Of the

eight essential amino acids, researchers have further narrowed the anabolic activity of essential amino

acids down to the branched-chain amino acids (often found in whey protein supplements).

Anabolic Effects of Branched-chain Amino Acids

The branched-chain amino acids (BCAAs) are leucine, isoleucine and valine. In many gym circles,

BCAAs seem to have been pushed aside in favor of creatine and other products for muscle growth.

Creatine is a great product, but it has no effect on human protein synthesis rates after resistance

undisputable. One study reported that when BCAAs were administered before a one-hour run, it

resulted in post-recovery elevations in GH and testosterone. The T response wasn't modified during the

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). BCAAs also help prevent

muscle protein breakdown during exercise. Protein synthesis in skeletal muscle is produced by intake of

a mixed meal and is largely due to BCAAs. For example, infusions of a mixture of amino acids

advantage for someone who wants to add muscle and who's dieting, as they have minimal calories,

they're metabolized strictly in muscle and they're highly anabolic.

Of all three BCAAs, leucine appears to be the most important for stimulating protein. More recent

studies have extended the earlier investigation to show that leucine is the most potent of the BCAAs in

enhancing mRNA translation of protein synthesis. In contrast to administration of either isoleucine or

valine alone, which have no effect on protein synthesis, leucine is unique as it's the most important

of leucine alone to fasted rats invoked the same stimulation of protein synthesis in skeletal muscle as

What's interesting about leucine is that it appears to be specific for muscle protein synthesis as

opposed to other organs. For example, oral administration of leucine has no effect on global rates of

protein synthesis in the liver, which many amino acids have. This means muscle seems to have first

dibs on leucine absorption, in contrast to other amino acids that are metabolized in the gut. Thus, it

impact on being incorporated into muscle than any other amino acid. A Swedish research study

reported that when patients had leucine infusions followed by muscle biopsies, increases in muscle

protein synthesis rates were observed and the intracellular concentrations of leucine increased

The research suggests that leucine is capable of stimulating muscle protein synthesis by itself.

BCAA/Leucine & Insulin: A Powerful Anabolic Combination

Leucine appears to regulate the energy status of the cell and intracellular concentrations of several

Supplemental leucine allows for a muscle to achieve maximum protein synthesis and anabolic

environment in muscle. Researchers tested how anabolic insulin was by itself and in conjunction with

amino acids. They found that insulin by itself was anti-catabolic in muscle by inhibiting protein

breakdown, whereas amino acids plus insulin largely increased protein anabolism by stimulating protein

synthesis and reducing muscle tissue breakdown. Thus, there's a synergistic effect between insulin and

amino acids. This is why it's so important to consume a combination carbohydrate/amino acid beverage

Subsequent studies have reported that insulin infused in the brachial artery in a fasted state caused a

20-fold increase, but failed to stimulate muscle protein synthesis and inhibited muscle protein

muscle protein synthesis rates as insulin by itself does not increase muscle protein synthesis rates.

To further support this research, if rats are administered diazoxide, which prevents a rise in insulin, the

of leucine is that it can stimulate protein synthesis through an insulin-independent mechanism. For

example, protein synthesis in diabetic rats is suppressed 35 percent, however, leucine administration to

diabetic rats increases protein synthesis by approximately 50 percent, but the rate remains below that

One of the problems researchers discovered when trying to identify the mechanism whereby leucine

increases protein synthesis is that leucine can stimulate insulin release. It was speculated that leucine

administration might have caused a rise in insulin, which enhanced protein synthesis rates. Subsequent

studies have shown that when arterial levels of leucine are measured after ingestion of BCAAs, no

significant increase in arterial insulin was detected. This suggests that leucine has a direct effect on

stimulate protein synthesis in skeletal muscle through both insulin-dependent and

independent mechanisms.

Fasting and calorie restriction result in an increase in leucine appearance rate in the blood- an index of

whole body protein breakdown. The increase in leucine appearance is consistent with a decline in

insulin, because insulin normally suppresses protein breakdown. Additionally, fasting increases the

glucocorticoids such as cortisol is characterized by a reduction in protein synthetic rate coincident with

hampered protein synthesis rates. However, oral administration of leucine reversed the catabolic effects

Get Your Swell on for Increased Protein Synthesis Rates!!

So, what is it about exercise that increases protein synthesis rates? Blood flow to working muscles is

greatly enhanced after exercise and blood is shunted away from other organs. This results in a greater

delivery of amino acids to muscle tissue and a low percentage of amino acids being absorbed by the

In animal studies, BCAAs, including leucine, were highly influenced by blood flow to muscles that

occurs during exercise, suggesting that leucine or BCAAs taken before exercise will greatly enhance

muscle protein synthesis rates due to enhanced blood flow to muscle. A recent study reported that

when insulin was infused into subjects, the change in muscle protein synthesis was predicted by

suggest that leucine, along with enhanced blood flow, significantly increases protein synthesis rates.

Leucine Increases mTOR

Leucine plays multiple roles in metabolism beyond the minimum requirement as an essential substrate

for synthesis of new proteins. The potential for leucine to impact protein synthesis, insulin signaling and

production of alanine and glutamine is dependent on dietary intake and increasing leucine

"Highlander amino acid: There can be only one!"

Leucine stimulates protein synthesis rates greater than any other amino acid. Additionally, a recent

study reported that the addition of leucine to a protein-based supplement led to a greater protein

synthesis than intake of the protein supplement alone when it was taken after a resistance exercise

It has now been established that leucine stimulates protein synthesis through signaling pathways that

mTOR is a master regulator of muscle growth (cell size and division) by sensing amino acid availability

important effects on stimulating a variety of growth signals, resulting in increased protein synthesis

rates. Resistance exercise, amino acids or a combination of both, are all known regulators of mTOR.

When BCAAs were administered to subjects during and after one session of leg extensions, an increase

muscle hypertrophy is unknown. Interestingly, IGF-1-dependent muscle hypertrophy is dependent on

the mTOR pathway. Studies have reported that if mTOR is inhibited by drugs, neither insulin, amino

evidence strongly suggests that mTOR plays a crucial role in controlling muscle cell growth.

Leucine for Reducing Appetite and Maintaining an Anabolic Environment

Another benefit of leucine has been found for weight training. mTOR is not only found in muscle, but

also in brain areas that regulate food intake. The research is still premature, but rats administered

leucine have a reduction in appetite. In several experiments, leucine decreases food intake.

Interestingly, another BCAA- valine- had no effect on food intake and didn't stimulate mTOR activity in

pathway with apparent modulation of the downstream signal for control of protein synthesis, resulting

in maintenance of muscle protein during periods of restricted energy intake.

Oral intake of 2.5 grams of leucine stimulates muscle protein synthesis after exercise or an overnight

conditions. Two weight-loss trials using diets designed to provide 10 grams per day of leucine (125

grams per day of dietary protein) with a minimum of 2.5 grams of leucine at each of three meals. In

comparisons with subjects following the USDA Food Guide Pyramid, subjects consuming the proteinrich

diets lost more weight and were more effective in correcting body composition during weight

lean tissue consistent with a protein-sparing mechanism for leucine. It seems reasonable that if a

strength competitor is getting ready for a competition, adding a few grams of leucine to his diet may

reduce appetite, yet still maintain an anabolic environment.

Leucine & Aging

Aging is associated with a decrease in muscle mass along with concomitant decrease in anabolic

hormones. In addition, there's also a decrease in protein synthesis, which has been termed "anabolic

resistance." This is shown by a decreased sensitivity and responsiveness of protein synthesis in muscle

both in rats and humans.

A recent study examined younger rats (8 months old) and older rats (22 months old) and found that

protein breakdown rates were higher in older rats compared to younger rats. But when older rats are

fed a diet supplemented with 5 percent leucine, there's a rejuvenation of muscle and an inhibition of

leucine-induced stimulation of muscle protein synthesis. When older animals are fed a high-leucine

supplemented meal, it will not only restore a significant stimulation of muscle protein synthesis, but

muscle protein wasting during aging.

'90s. The reported anabolic effects of BCAAs, particularly leucine, have caught the eye of many

researchers in terms of increasing muscle mass and reducing muscle breakdown. It's been known for

many years that muscle hypertrophy comes about via an increase in the rate of protein synthesis.

Leucine and BCAA have potent anabolic effects by increasing mTOR activity, resulting in enhanced

activation of muscle proteins. Carbohydrates, nonessential amino acids and other amino acids don't

have the stimulatory effects on protein synthesis when compared with leucine. However, in most cases,

the combination of BCAAs with carbohydrates produces an additive effect on the stimulation of the

mTOR pathway, producing maximal rates of protein synthesis during recovery.

By Robbie J. Durand, MA