BCAAs are essential amino acids that bodybuilders use. BCAAs help many athletes increase power output, reduce fatigue, and improve fat loss [R, R, R, R].

However, excessive BCAA usage can have negative side effects, such as reducing performance and increasing the risk for type 2 diabetes. Read on for further detail on correct dosage and what else BCAA supplements can do for you [R, R].

What are BCAAs?

There are three BCAAs: leucine, isoleucine, and valine, which are all essential amino acids not produced by the body but needed for survival [R, R].

BCAAs are the largest collection of amino acids in the body, accounting for up to 35% of muscle proteins [R].

Normally, BCAAs are excreted rapidly. BCAA intermediates can be toxic at high concentrations, so functional BCAA breakdown is vital [R, R].

BCAA formulas have been on the market since 1996, mainly for treating liver diseases such as cirrhosis and hypoalbuminemia [R].

Nowadays, BCAAs are mainly used by bodybuilders for exercise purposes, to increase energy, and to boost protein synthesis (especially leucine) [R].

BCAAs Health Benefits

1) BCAA Supplementation Improves Exercise Performance

Exercise leads to amino acid usage. BCAAs become rapidly depleted after exercise, showcasing the possible beneficial effects of BCAA supplementation [R].

In a double-blind randomized controlled trial (DB-RCT) of 218 marathon runners, BCAA supplementation improved mental performance [R].

The running times of slower athletes improved, but there were no improvements in faster runners [R].

In a study (DB-RCT) of 12 volunteers, BCAA supplements increased power output. However, decreased fatigue and exertion may be the cause of the power elevation [R, R].

In another DB-RCT of 36 males, BCAA supplementation increased their muscle strength more compared to other supplements, like whey protein and carbohydrate supplements [R].

This effect could be caused by increases in cortisol as seen in a DB-RCT of 10 volunteers. Cortisol controls the fight-or-flight response, which can flood muscles with glucose, providing brief but great amounts of energy [R].

However, a study of 12 athletes found no increases in handgrip strength following BCAA supplementation [R].

Moreover, excessive BCAA supplementation can decrease exercise performance. A rat study showed that a 3.57% BCAA-supplemented diet increased swimming time until exhaustion by 37%. However, a higher (4.76%) BCAA-supplemented diet decreased swimming times by 43% compared to the controls [R].

BCAA Supplementation Reduces Fatigue and Increase Endurance

In a study (DB-RCT) of 218 marathon runners, BCAA supplementation reduced fatigue after a race. In another DB-RCT of 7 volunteers, their fatigue decreased by an average of 17.2% [R, R].

Similarly, BCAA supplementation can increase endurance. In a DB-RCT of 10 endurance runners, the runners given BCAA supplements ran better times for two consecutive days in a row in both 5,000 and 10,000 m races [R].

BCAA supplements also increase lactate threshold (LT) in a study (DB-RCT) of 8 volunteers. LT measures endurance capacity as any exercise below the LT means lactate does not build up in the muscles [R].

Oxygen consumption (VO2) is a measure of LT and the study showed that overall VO2 measures increased by 13% and max VO2 increased by 4.2% [R].

However, a DB-RCT of 10 volunteers undergoing aerobic exercise showed that BCAA supplementation had no effect on fatigue. There are other studies that have validated these results [R, R].

Furthermore, excessive BCAA supplementation leads to increased ammonia production, promoting fatigue [R].

BCAA Supplementation May Improve Fat Loss

In a DB-RCT of 7 volunteers, BCAA supplementation increased fat loss which is associated with improvements in aerobic exercise [R].

However, in a DB-RCT of 24 skiers, BCAA supplementation caused less weight loss (as opposed to fat loss) compared to the controls (1.2% compared to 2.1%) [R].

BCAA Supplementation Increases Lean Mass

In a DB-RCT of 36 body-builders, BCAA supplements increased lean mass by an average of 4 kg, which was more than other bodybuilding supplements like carbohydrate supplements and whey protein [R].

BCAA Supplementation May Reduce Soreness

In a DB-RCT of 12 healthy female volunteers, BCAA supplements decreased delayed-onset muscle soreness (DOMS) by 80%. Soreness reduces exercise performance in subsequent days [R].

However, in a DB-RCT of 21 older volunteers, BCAA supplementation did not improve muscle soreness [R].

BCAA Supplementation May Reduce Muscle Damage

Supplementing with BCAAs decreases protein degradation in the muscles [R].

Additional studies have shown that supplementation with a metabolite of leucine (HMB) led to lower levels of enzymes that indicate muscle damage [R].

BCAA Supplementation May Increase Short-Term Memory Performance After Exercise

A DB-RCT of 12 volunteers showed that after exercise athletes without BCAA supplementation had reduced short-term memory. Memory performance in BCAA supplemented volunteers did not decrease [R].

BCAA Supplementation May Decrease Reaction Times

In a DB-RCT of 10 soccer players, those given BCAA supplements showed a decrease of up to 10% in reaction time compared to the controls [R].

BCAA Supplementation May Reduce Perceived Exertion

In a DB-RCT of 7 cyclists, BCAA supplementation reduced the exertion that was perceived by the athletes by up to 7%. However, even if their exertion was lower, their exercise performance did not change [R].

BCAA Supplementation Reduces Perceived Pain

Norepinephrine is released in the brain to manage pain. BCAA supplementation in rats increased norepinephrine, thereby, reducing pain [R].

BCAA Supplementation Improves Breathing

BCAA supplementation decreased blood CO2 levels by 9%, which normally increases with exercise [R].

It also increased average oxygen intake (by 19%) and minute ventilation (by 22%), which measures the volume of gas inhaled by the lungs per minute [R].

Finally, BCAA supplementation increases ventilatory response, which allows the body to process and receive oxygen at higher rates [R].

BCAA Supplementation Does Not Affect Heart Rate

Although some BCAA users mention it as a typical concern before starting supplementation, scientific evidence shows that BCAAs don’t affect heart rate by themselves.

In a study of 12 men taking BCAA and carbohydrate supplements, the supplements did not increase heart rate [R].

Other studies showed that heart rate did not change, or that it even decreased [R ,R, R].

The increased heart rate seen by some users may be due to other components in the supplements such as caffeine.

2) BCAA Supplementation May Improve Liver Health

In one DB-RCT, BCAA supplementation not only increased nutritional status but also improved sleep and decreased fatigue in liver cirrhosis patients [R].

Furthermore, in a DB-RCT of 16 controls, 20 chronic hepatitis patients, and 100 cirrhosis patients, BCAA supplementation greatly increased albumin in the blood, which leads to declines in both liver diseases [R].

Liver survival rate without any detrimental event was around 63.6% with BCAA supplementation [R].

3) BCAA Supplementation Can Help the Kidneys

BCAA supplementation reduces the chances of kidney failure by up to 40%. It increases amino acid levels but not protein intake, which decreases kidney damage [R, R].

BCAA supplementation also improved appetite and nutrition in dialysis patients [R].

4) BCAA Supplementation May Prevent Heart Failure

In rat studies, BCAA supplementation improved outcomes after induced heart failure and cardiac cachexia (severe weight loss), improving functions such as [R]:

  • Decreased heart rate
  • Increased heart function
  • Increased survival time
  • Decreased weight loss
  • Increased mitochondrial function

In humans, BCAA breakdown deficiencies are linked to increased heart disease risk [R].

5) BCAAs May Increase Energy

During states of increased amino acid levels, the amino acids will compete with glucose to provide energy, thereby becoming a secondary source of energy. In one study, people with high levels of amino acids required 36% less glucose [R].

In rats, isoleucine (a BCAA) decreased glucose usage by 20% in the blood and 71% in the muscles [R, R, R].

Isoleucine and valine can also be converted to glucose for energy [R].

One gram of BCAA is around 4 calories [R].

6) BCAAs May Improve Insulin Resistance and Diabetes

Insulin resistance increases blood sugar levels. In a DB-RCT of 27 patients suffering from either insulin resistance or hepatitis C, BCAA supplements improved muscle insulin resistance in 10 of the patients (but remained unchanged in the rest) [R].

Moreover, BCAA levels can be used to predict insulin resistance. In a weight-loss study of 500 participants, insulin resistance was correlated with increased BCAA levels [R].

Insulin resistance is the most common cause of type 2 diabetes. In a long-term study of 2,422 subjects, after 12 years, 201 patients with insulin resistance developed type 2 diabetes and had higher levels of BCAAs [R].

Also, urine leucine levels were significantly higher in 55 type 2 diabetes patients [R].

BCAA supplementation itself increases the risk for type 2 diabetes. In a 15 year study of 155 middle-aged women, increasing BCAA intake by up to 20% increased the risks of type 2 diabetes by 7% [R].

7) BCAA Supplementation May Improve Sleep

Some patients with kidney problems develop sleep disorders such as sleep apnea, which can reduce sleep quality and time [R].

In a study of 7 patients, taking BCAA supplements at night increased rapid eye movement (REM) sleep and decreased end-tidal CO2 levels, which are important for dreaming and respiratory function during sleep [R].

Limitations of BCAA Supplementation

BCAA mechanisms and amino acid ratios for treating muscle damage and soreness are still unknown [R].

Also, BCAA supplementation may interfere with the absorption of other amino acids. The blood-brain barrier uses similar mechanisms for amino acid absorption. Extra BCAA supplementation can lead to decreased absorption of tryptophan, tyrosine, and glutamine [R, R].

Side Effects of BCAA Supplementation

1) BCAA Supplementation Can Lead to Hyperammonemia

BCAA supplementation increases ammonia levels in the blood (hyperammonemia), which can lead to a variety of different brain disorders such as Reye syndrome and deficiencies of urea cycle enzymes [R].

Furthermore, hyperammonemia leads to increased fatigue [R].

2) BCAA Supplementation May Lead to Amyotrophic Lateral Sclerosis (ALS)

ALS is one of the most common neuromuscular diseases, especially in athletes. This is caused by increased BCAA levels, leading to increased excitation of certain neurons [R].

These neurons become hyperexcited to toxic levels, causing ALS [R].

3) BCAA Supplementation Decreases Absorption of other Amino Acids

Aromatic amino acids (phenylalanine, tyrosine, and tryptophan) compete with BCAAs in getting absorbed into the brain [R,R].

Phenylalanine and tyrosine increase dopamine. Therefore, BCAA supplements may reduce dopamine [R,R,R].

BCAA Dosage

There is still not enough data for correct dosing of BCAA. However, one study (DB-RCT) found that 0.087g/kg at a 2:1:1 ratio (leucine:isoleucine:valine) improved performance factors such as strength and decreased soreness [R].

The recommended dosage for leucine, one of the BCAAs, in bodybuilding for an average weight male is around 35 grams/day [R].

It is recommended to take BCAA supplements before and after exercise to reduce muscle damage [R].

It is important to remember excessive dosing can have the opposite effect and worsen performance. In one rat study, excessive BCAA supplements increased fatigue [R].

Although there is clinical data on toxic doses on rat studies, human data is not available [R].

Forms of Supplementation

BCAAs can be supplemented as:

The powder or lemonade forms tend to taste worse but are the most popular. This is because you have to take a lot of capsules or tablets to get the recommended amount and they take longer to digest.

Also, foods high in protein content such as chicken, turkey, beef, pork, milk, and cheese will be high in BCAA content [R].

Drug Interactions

BCAA with morphine, a pain medication, increases the effectiveness and duration of the pain relief [R].

Synergies with Other Supplements

In a DB-RCT of 10 endurance runners, combining BCAA supplements with arginine and citrulline supplements improved run time. While BCAA supplementation can increase ammonia levels, arginine and citrulline both decrease them, thus having a protective effect [R].

Contraindications of BCAA Supplementation

People with various diseases should not take BCAA supplements.

Patients with McArdle’s disease uptake and degrade BCAA at much higher rates. When they took BCAA supplements, their heart rates spiked and exercise performance decreased [R].

Maple Syrup Urine Disease is caused by deficiencies in the molecule responsible for BCAA breakdown (branched-chain α-keto acid dehydrogenase). These individuals will have unusually high levels of BCAA, and supplementation could worsen their symptoms [R].

BCAA Supplements Should Be Warily Taken by Diabetics

Although not fully validated, BCAA supplementation has been shown to conserve blood glucose and glycogen levels. Diabetics should be wary of taking BCAA supplements, especially during exercise when glucose levels should decrease since BCAA supplements help to conserve glucose levels [R].

BCAA-related Genes

In a study of 73 obese and 77 lean patients, BCAA levels were significantly higher in obese patients. BCAA supplementation can lead to activation of certain pathways such as mTOR, S6K1, and IRS1, which can lead to insulin resistance [R].

Krüppel-like Factor 15 (KLF15) is a key regulator of the heart’s BCAA catabolic pathway. Defective KLF15 increases levels of branched-chain α-keto acids (BCKA), which are known to promote heart defects and failure [R].

User Reviews

BCAA supplement users say that their workouts have improved heavily. One user states that the BCAA supplements have helped even during their “cutting” phase [R].

Other reviews mention that it is hard to go wrong with BCAA supplements no matter the brand [R, R].

FDA Compliance

The information on this website has not been evaluated by the Food & Drug Administration or any other medical body. We do not aim to diagnose, treat, cure or prevent any illness or disease. Information is shared for educational purposes only. You must consult your doctor before acting on any content on this website, especially if you are pregnant, nursing, taking medication, or have a medical condition.


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