People buy BCAA supplements to increase muscle mass and enhance performance during exercise. Branched-chain amino acids are useful because they help activate vital enzymes during muscle protein synthesis.
So what are BCAAs, and what do they do? Branched-chain amino acids (BCAAs) are a sub-category of essential amino acids. The essential amino acids that most people are interested in are: leucine, isoleucine, and valine because of the vital role these amino acids play in muscle development.
15 Potential Benefits of BCAAs
- Boosts Strength
- Aids Weight Loss
- Prevents Muscle Loss
- Improves Coordination
- Assists Muscle Recovery
- Increases Muscle Growth
- Reduces Exercise Fatigue
- Reduces Muscle Soreness
- Increases Insulin Secretion
- Prevents Liver Disease
- Reduces Mental Fatigue
- Supports Immune Function
- Improves Cognitive Function
- Improves Body Composition
- Stimulates Muscle Protein Synthesis
BCAAs are incredibly popular in the fitness world. Whether you take BCAAs before, after, or during a workout, BCAAs are said to prevent muscle breakdown and aid muscle growth.
However, some people argue that taking BCAAs is redundant because every time we consume protein, we also consume essential amino acids. For example, whey protein powder, on average, contains up to 11 grams of leucine, 6 grams of isoleucine, and 6 grams of valine.
Food-wise, chicken contains around 6.6 grams of branched-chain amino acids for a 6 ounce portion. In comparison, salmon contains approximately 5.9 grams for the same portion size with essential amino acids in varying amounts.
BCAAs represent around 40% of all vital amino acids in the body, with the muscles containing approximately 18% of all BCAAs. However, contrary to other amino acids, BCAAs are broken down in the muscles instead of the liver; this is why many people believe that BCAAs play an essential role in energy production during exercise.
Besides stimulating muscle protein synthesis, BCAAs also decrease cognitive fatigue during extended periods of activity. The potential to reduce mental fatigue may prove beneficial for increasing physical endurance in athletes. However, one of the main concerns surrounding BCAA supplements is BCAAs bioavailability once it enters the body.
As BCAAs have poor hydrophilic performance, meaning BCAAs are not soluble in water, they struggle to dissolve in the digestive tract. This insolubility means that despite taking high concentrations of BCAAs, your body is unable to absorb 100% of the BCAAs you consume.
Dietary Sources of BCAAs
If you wish to add more BCAAs to your diet, the following foods contain high amounts of Branched-Chain Amino Acids:
- Soy products
- Pumpkin seeds
- Milk and Cheese
- White and red meat
- Legumes, beans, peas, and lentils
There is also the option to take BCAA supplements. BCAA supplements come in either powder or capsule form. You can purchase BCAA supplements and mix them into liquids such as water or a protein shake.
BCAAs contain three essential amino acids: isoleucine, leucine, and valine. In most cases, BCAA supplements include twice the amount of leucine than valine or isoleucine, and this is known as a 2:1:1 ratio.
BCAA supplements offer this ratio because leucine is, according to research published in the Journal of Nutrition, effective at stimulating muscle protein synthesis and suppressing the breakdown of protein in muscles.
The Nine Essential Amino Acids
There are nine essential amino acids that play an indispensable role in muscle protein synthesis and glucose regulation. These nine essential amino acids work in different ways.
Histidine: is the base of histamine, the neurotransmitter involved in immune reactions, digestion, sexual function, and the circadian rhythm/sleep-wake cycle. Histidine is also crucial for maintaining the protective barrier surrounding nerve cells.
Isoleucine: is a branched-chain amino acid that plays a vital role in muscle metabolism, immune system support, the production of hemoglobin, and energy production and regulation.
Leucine: is one of the most important BCAAs. Leucine is needed for muscle protein synthesis and repair. Aside from this, leucine plays a role in blood glucose regulation, wound healing, and growth hormone production.
Lysine: is an amino acid that plays a role in muscle protein synthesis, hormone production, as well as the absorption of calcium.
Lysine also serves an important function in energy production, immune support, and the production of structural proteins like collagen and elastin.
Methionine: is an amino acid that’s important for metabolic functioning and the detoxification process.
Phenylalanine: is the precursor amino acid for several important neurotransmitters, including tyrosine, dopamine, epinephrine, and norepinephrine.
Phenylalanine plays an essential role in the structure and function of proteins and enzymes, contributing to the formation of other amino acids.
Threonine: is an important component of structural proteins like collagen and elastin, both of which are crucial for healthy skin and connective tissue. Threonine also contributes to fat metabolism and optimal immune functioning.
Tryptophan: often thought to be the cause of drowsiness after eating turkey, is crucial for maintaining the correct balance of nitrogen in the body.
Valine: as a constituent of BCAAs, helps to stimulate muscle protein synthesis and enhance energy production.
As you can see from this list, these nine essential amino acids play a vital role in maintaining and supporting the body.
BCAAs and Muscle Growth
A study published in the European Journal of Clinical Nutrition examined a group of healthy women who took part in regular resistance exercise. The women took 2 grams of leucine and 5 grams of BCAAs before and after each training session and on rest days as well. The results of the study found that BCAA supplements did not have an impact on the women’s body composition or muscle mass.
Likewise, another study published in the American Journal of Clinical Nutrition looked at untrained, healthy men who performed consistent weight training workouts.
In the study, the men took BCAA supplements that provided 2.25 grams of leucine and 4.5 grams of BCAAs before and after each training session (with four sessions each week).
Again, the researchers found no impact on body composition, either positive or negative, when supplementing with BCAAs. Further research by McMaster University examined resistance-trained men who consumed a diet high in protein.
In the study, the men took 3.5 grams of leucine and 7 grams of BCAAs before and after each training session. At the end of the study, the researchers found that BCAA supplements preserved muscle mass and had a positive effect on muscle protein synthesis. Unfortunately, other researchers have criticized this study for dubious data reporting, which may have led to flawed conclusions at the end of the study.
An article published in the International Journal of Sports Medicine examined the effect of BCAAs on elite wrestlers who had a lean body fat percentage of 6–8 percent.
The study found that BCAAs didn’t preserve muscle mass, but did provide a boost to fat loss during a hypo-caloric diet that was quite aggressive and took place over 19-days.
However, it’s important to note that the wrestlers’ protein intake was low (about 1 gram for every 2.2 pounds of bodyweight), and the BCAA dose (67 grams of BCAAs per day, which included 50 grams of leucine) was too high for regular consumption.
Leucine and Muscle Mass
A study published in Sports Medicine looked at the quantity of BCAAs and the impact of BCAA ingredients on muscle mass. The study found that BCAA supplements that have more leucine are more effective when it comes to increasing muscle mass; this is likely due to leucine’s anabolic effect on protein metabolism.
As leucine increases muscle protein synthesis rates, BCAAs with a high leucine ratio are in a better position to protect and support muscles. The omission of leucine has been shown to inactivate mTOR signaling, which results in the breakdown of muscle proteins.
This finding doesn’t mean that isoleucine and valine are useless. Isoleucine and valine are necessary for the production of energy and the regulation of blood sugar levels.
BCAAs and Muscle Protein Synthesis
Research into muscle protein synthesis shows that rates of muscle protein synthesis tend to slow down at or after the age of twenty. However, muscle protein synthesis for athletes is more dependent on muscle usage than age.
Remember, all forms of intense physical activity send direct stress to the muscles. During exercise, muscles break down through a process known as catabolism, which involves the separation of muscle fibers.
The subsequent repair of muscles is known as anabolism—the process where muscle protein synthesis occurs, leading to muscle growth and development.
BCAAs are said to promote cell signaling and protein synthesis through the activation of the mTOR pathway; mTOR is the central regulator of several processes in the body that contribute to cell growth, cell proliferation, cell migration, and muscle growth.
There are, however, studies that suggest that BCAA supplementation alone cannot support an increased rate of muscle protein synthesis. In this case, the rate of muscle protein synthesis requires the availability of all amino acids, not just branched-chain amino acids.
With BCAA supplements, you increase the amount of available leucine, isoleucine, and valine, but the availability of other essential amino acids is limited.
Can BCAAs Alone Build Muscle?
A study reported in Frontiers in Physiology found that BCAAs do not build muscle. In the study, 25 grams of whey protein, which contained 3 grams of leucine and 6.25 grams of protein, were mixed with essential amino acids.
After three hours, the study found that all three supplements stimulated muscle protein synthesis, but in the fifth hour, only pure whey protein stimulated muscle protein synthesis.
Another follow-up study by Canadian researchers investigated what would happen if they gave an increased dose of leucine to men. After resistance exercise, 24 healthy, young men (split into two groups) took either whey protein with 4.25 grams of leucine or whey protein with 2.25 grams of leucine.
The study found that whey protein with 4.25 grams of leucine stimulated muscle protein synthesis, while whey protein with 2.25 grams of leucine did not improve muscle protein synthesis levels.
The same study discovered that whey protein mixed with BCAAs stimulated lower levels of muscle protein synthesis compared to whey protein mixed with 4.25 grams of leucine.
This study suggests that leucine stimulates more muscle growth when consumed on its own without the presence of isoleucine and valine. The reason this occurs is likely due to isoleucine and valine competing with leucine for absorption in the gut and entry into muscle tissues.
BCAAs and Exercise Performance
Another study published in the Journal of the International Society of Sports Nutrition found that people who took BCAAs performed 20% better on strength training tests. In the study, when the participants repeated the same strength-training tests after 24 to 48 hours, it was found that there was a “possibility” that BCAAs also improved their recovery time.
St. Mary’s University school of health and Applied Science performed a study on 16 resistance-trained athletes and found that branched-chain amino acids improved muscle recovery and performance and also led to a decrease in muscle soreness.
Another research study by the Department of Community Nutrition at Tehran University showed that if you supplement with BCAAs, you will receive more muscle recovery benefits and reduce muscle soreness compared to supplementing with other products.
Researchers discovered that taking 4 grams of leucine per day increases the strength performance of non-athletic people. These studies indicate that BCAAs are beneficial for both trained and untrained individuals.
BCAAs and Muscle Damage
It seems that BCAAs have the potential to slow down muscle loss, but cannot stop or prevent muscle loss altogether. The Department of Rehabilitation in Midorigaoka Hospital in Japan carried out a 10-day study on 22 older adults committed to a hospital bed.
The study found that patients who received 15 grams of mixed amino acids increased their muscle function, while patients who used a placebo had 30% less muscle function in comparison.
BCAAs can also decrease the extent of Delayed Onset Muscle Soreness after a hard training session. The leading theory behind this is that BCAAs help to reduce serum levels of intramuscular enzymes associated with muscle damage and high creatine kinase levels.
A study of 16 male athletes who participated in 120 minutes of cycling at 70% of their VO₂ max found that athletes who supplemented with BCAAs over 14-days experienced a significant decrease in creatine kinase levels compared to athletes who took no BCAAs.
Another study published in the Journal of the International Society of Sports Nutrition examined 12 male athletes who performed damaging muscle exercises.
The study found that BCAA supplementation decreased creatine kinase concentrations. This decrease in creatine kinase indicates less muscle damage and improved recovery rates compared to athletes who used a placebo instead of a BCAA supplement.
Furthermore, a study by Nagoya University found that Delayed Onset Muscle Soreness peaked 2–3 days after exercise; however, muscle soreness was significantly lower in people who supplemented with BCAAs.
BCAAs and Weight Loss
According to the Gillings School of public health, people who consumed approximately 15 grams of BCAAs every day lowered their chance of being overweight or obese by a significant amount.
In another study, wrestlers who consumed a high-protein diet, supplementing with BCAAs, lost around 3.5 pounds (or 1.6 kilograms) more weight than wrestlers who consumed a soy protein supplement. The BCAA group also lost 0.6% more body fat than the soy protein group.
Further research on weightlifters examined how BCAAs affect weight loss. In the study, the weightlifters consumed 14 grams of BCAAs per day. After 8-weeks, the study found that weightlifters who took BCAAs experienced a 1% body fat reduction compared to weightlifters who took 28 grams of whey protein. However, more research and studies are needed to confirm these results.
BCAAs and Exercise Fatigue
According to central fatigue theory, excess serotonin crosses the blood-brain barrier during physical activity, which contributes to feelings of fatigue.
Altering serotonin activity curbs various psychological responses like lethargy, sleepiness, and mood changes, which makes us feel more awake. When we alter the ratio of tryptophan to BCAAs by increasing the amount of BCAAs in our diet, we limit the amount of serotonin that the brain receives, decreasing feelings of tiredness.
A Swedish study of male endurance cyclists examined the effects of branched-chain amino acids on perceived exertion after 80 minutes of exercise. In the study, after consuming BCAAs, cyclists’ perceived ratings of exertion were 7% lower, and evaluations of mental fatigue were 15% lower than cyclists who took a placebo.
Another study conducted by the Université d’Orléans examined a group of sailors in a 32 hour offshore sailing race. After the race finished, the researchers found that the detrimental effects of fatigue were significantly lower in the sailing group that consumed a high protein diet rich in BCAAs.
Furthermore, researchers at Rutgers University examined the effects of BCAA supplementation on cycling performance. In the study, cyclists who consumed BCAAs cycled for 12% longer than cyclists who took a placebo supplement.
While these studies show promise, other studies report no association between BCAA supplements and decreased fatigue.
Effectiveness of BCAAs
Studies show that whole proteins with a complete amino acid profile lead to more muscle growth than taking BCAAs. Research also indicates that BCAA supplements don’t promote muscle growth in healthy young adults. While some studies show promising results for BCAA supplements, further research is needed.
Still, the fact remains that BCAA supplements are a multi-million dollar industry based around the belief that taking BCAAs keeps the body in an anabolic state and stimulates muscle protein synthesis. While there is some truth to these claims, it seems that BCAAs are only useful in the absence of sufficient protein in a person’s diet.
Long-story-short, essential amino acids are critical to your overall health and well-being, and BCAAs do not provide the body with all the essential amino acids it needs. In this respect, as a supplement, whey protein offers a more complete amino acid profile than BCAAs.
There is no need to take a BCAA supplement if you already have enough protein in your diet. Eating a protein-rich diet will cover all your BCAA needs without the need to supplement with additional BCAA products.
If you want to supplement with BCAAs, you’re better off taking whey protein or egg protein, as these supplements provide you with all the essential amino acids your body needs.