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Branched-chain amino acids (BCAAs) are a group of three essential amino acids:

• leucine
• isoleucine
• valine

BCAA supplements are commonly taken to boost muscle growth and enhance exercise performance. They may also help with weight loss and reducing fatigue after exercise.

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This article contains all the most important information about branched-chain amino acids and their benefits.

What are BCAAs?

BCAAs consist of three essential amino acids:

• leucine
• isoleucine
• valine

These amino acids are grouped together because they are the only three amino acids to have a chain that branches off to one side.

Like all amino acids, BCAAs are building blocks your body uses to make proteins.

BCAAs are considered essential because, unlike nonessential amino acids, your body cannot make them. Therefore, it is essential to get them from your diet.

The three BCAAs are leucine, isoleucine, and valine. All have a branched molecular structure and are considered essential to the human body.

How do branched-chain amino acids work?

BCAAs make up a large chunk of the body’s total amino acid pool.

Together, they represent around 35–40% of all essential amino acids present in your body and 14–18% of those found in your muscles (1).

Contrary to most other amino acids, BCAAs are mostly broken down in the muscle, rather than in the liver. Because of this, they are thought to play a role in energy production during exercise (2).

BCAAs play several other roles in your body.

First, your body can use them as building blocks for protein and muscle (3, 4, 5).

They may also be involved in regulating your blood sugar levels by preserving liver and muscle sugar stores and stimulating your cells to take in sugar from your bloodstream (6, 7, 8, 9).

What’s more, BCAAs may help reduce the fatigue you feel during exercise by reducing the production of serotonin in your brain (10).

Out of the three, leucine is thought have the biggest impact on your body’s capacity to build muscle proteins (3, 11).

Meanwhile, isoleucine and valine seem more effective at producing energy and regulating your blood sugar levels (6, 12).

Your body can use BCAAs to build muscle protein and produce energy. They may also have an effect on your brain that reduces fatigue.

BCAAs may reduce fatigue during exercise

Consuming BCAAs may help reduce physical and mental fatigue.

A study reports that consuming 20 grams of BCAA dissolved in 400 mL of water and 200 mL of strawberry juice 1 hour before working out increases time to exhaustion in participants (13).

In another study, it was found that participants reported up to 15% less fatigue in those given BCAAs during exercise, compared with those who were given a placebo (14, 15).

In one study, this increased resistance to fatigue helped the BCAA group exercise for 17% longer before reaching exhaustion compared with the placebo group (12).

However, not all studies found that decreased fatigue caused improvements in physical performance (14, 16, 17).

In some people, BCAAs may help reduce exercise fatigue. Whether this improves exercise performance is still up for debate.

BCAA supplements reduce muscle soreness

BCAAs may also help your muscles feel less sore after exercise.

One way they may do so is by lowering blood levels of the enzymes creatine kinase and lactate dehydrogenase, which are involved in muscle damage. This may improve recovery and provide some protection against muscle damage (18).

Various studies asked participants to rate their muscle soreness levels after performing certain strength-training exercises.

Participants who were given BCAA supplements rated their muscle soreness levels as much as 33% lower than those given a placebo (19, 20, 21).

In some cases, those given BCAAs also performed up to 20% better when they repeated the same strength-training tests 24–48 hours later (22, 23).

However, effects may vary based on your gender or the total protein content of your diet (19, 24).

BCAAs taken before or after strength training may reduce muscle soreness following your workout. However, the effects may vary from one person to another.

BCAAs may increase muscle mass

Some people who purchase BCAA supplements do so to increase their muscle mass.

After all, research shows that BCAAs do activate enzymes responsible for building muscle (25).

Some studies also show that BCAA supplements may be effective at increasing muscle mass, especially if they contain a higher proportion of leucine than isoleucine and valine (25, 26).

However, there’s currently no evidence that getting your BCAAs from a supplement is any more beneficial than getting them from your diet or from a whey or soy protein supplement.

In fact, studies show that taking supplements with whole protein may, at least in some cases, be better for muscle growth than taking supplements with individual amino acids (27).

Getting enough BCAAs may boost muscle growth. You can get them from high protein foods in your diet or through supplements.

BCAAs may lower blood sugar levels

BCAAs may also help maintain normal blood sugar levels.

Leucine and isoleucine are thought to increase insulin secretion and cause your muscles to take in more sugar from your blood, thereby decreasing your blood sugar levels (28, 29).

However, in practice, not all studies back up these effects (30, 31).

In fact, some even report potential rises in blood sugar levels, depending on the type of diet participants followed. For instance, when BCAAs are combined with a high fat diet, consuming them in supplement form may lead to insulin resistance (32, 33).

That said, many of these studies were done on animals or cells, which means that their results may not be totally applicable to humans.

In humans, effects also seem to vary between participants.

For example, in one recent study participants with liver disease were given 12.5 grams of BCAAs three times per day. In 10 participants, blood sugar levels were reduced, while 17 participants experienced no effects (34).

More studies are needed before strong conclusions can be drawn.

BCAAs may help promote blood sugar management, at least in some cases. However, more studies are needed to confirm their effects.

BCAAs may enhance weight loss

Branched-chain amino acids may help prevent weight gain and enhance fat loss.

In fact, observational studies report that those consuming an average of 15 grams of BCAAs from their diet each day may have up to 30% lower risk of becoming overweight or having obesity than those consuming an average of 12 grams per day (35, 36).

However, it’s worth noting that those consuming fewer BCAAs also consumed around 20 fewer grams of total protein per day, which may have influenced results.

If you’re attempting to lose weight, BCAAs may help your body get rid of unwanted fat more effectively.

Competitive wrestlers consuming a high protein, calorie-restricted diet supplemented with BCAAs lost 3.5 more pounds (1.6 kg) than those given a soy protein supplement over a 19-day study period (37).

The BCAA group also lost 0.6% more body fat than the soy protein group, despite consuming equivalent calories and slightly less total protein each day (37).

In another study, weightlifters given 14 grams of BCAAs per day lost 1% more body fat over an eight-week study period than those given 28 grams of whey protein per day. The BCAA group also gained 4.4 pounds (2 kg) more muscle (38).

That said, these two studies have some flaws. For instance, they provide little information about the composition of the supplement and of the diet followed, which could have influenced the outcomes.

What’s more, studies examining the effects of BCAAs on weight loss show inconsistent results (39).

BCAAs may help prevent weight gain and enhance weight loss. However, more research is needed to determine whether supplements provide any added benefits over a high protein diet.

BCAAs may reduce complications in liver disease

BCAAs may help reduce complications linked to liver failure.

One possible complication is hepatic encephalopathy (HE), which can lead to confusion, loss of consciousness and coma.

A 2014 review suggests that in patients with liver disease, BCAA supplements may be more beneficial than other supplements at reducing the severity of HE (40).

However, BCAAs did not improve overall survival rate, and they didn’t lower the risk of other complications, such as infections and gastric bleeding (40).

Another review of studies in patients undergoing liver surgery reported that BCAA-enriched solutions may help improve liver function, reduce the risk of complications, and decrease the duration of hospital stay (41).

BCAA supplements may also be effective at reducing fatigue and improving weakness, sleep quality, and muscle cramps in individuals with liver disease (42).

In cases of liver cancer, taking BCAA supplements may help reduce water retention and decrease the risk of premature death (43).

However, if you have liver disease, please speak with your healthcare team about using BCAA supplements before starting them.

BCAA supplements may be effective at improving liver function and decreasing the risk of complications in individuals who have liver disease.

Dosage instructions

If you’d like to start supplementing with branched-chain amino acids, you should speak with a healthcare professional to decide if it’s right for you and how much you should take.

Furthermore, there are no official recommended daily requirements for BCAA though there are studies that have suggested different amounts (44, 45).

However, people who include sufficient protein-rich foods in their diets most likely do not need to take supplements.

The best time to take BCAA supplements is before and/or after your workout. Many people who are trying to gain muscle also take them in the morning and before bed.

However, whether the exact timing makes a big difference for this has not been studied properly. But you should follow the manufacturer’s instructions and do not exceed the maximum listed dosage.

There is no official recommended dose for BCAAs, and since a diet that is sufficient in protein-rich foods may be all you need, you should speak with a healthcare professional before supplementing.

Top food sources

Luckily, there’s a large variety of foods that contain BCAAs such as:

• meat, poultry, and fish
• beans and lentils
• dairy items such as cheese and milk
• tofu and tempeh
• eggs
• quinoa
• nuts and seeds

Adding foods from the list above to your diet will help you increase the amount of BCAAs you get each day.

Safety and side effects

Taking BCAA supplements is generally safe and without side effects for most people.

However, individuals with a rare congenital disorder called maple syrup urine disease should limit their intake of BCAAs because their bodies cannot break them down properly (46).

Taking BCAA supplements is generally safe, but BCAA supplementation is not recommended for some people.

The bottom line

Branched-chain amino acid supplements may provide impressive benefits in certain circumstances, especially when it comes to muscle growth and physical performance.

However, BCAAs can also be found in whole protein supplements as well as in a large variety of protein-rich foods.

Therefore, taking BCAA supplements may not be necessary, especially if you get sufficient amounts through your diet or a protein supplement.