Branched-chain amino acids (BCAAs) are a group of three essential amino acids: leucine, isoleucine and valine.
BCAA supplements are commonly taken in order to boost muscle growth and enhance exercise performance. They may also help with weight loss and reduce fatigue after exercise.
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:
These amino acids are grouped together because they are the only three amino acid to have a chain that branches off to one side.
Their molecular structure looks like this: Image Source: Like all amino acids, BCAAs are building blocks your body uses to make proteins.
BCAAs are considered essential because, unlike non-essential amino acids, your body cannot make them. Therefore, it is essential to get them from your diet.
Bottom Line: 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 ().
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 ().
BCAAs play several other roles in your body too.
First, your body can use them as building blocks for protein and muscle (, , ).
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 (, , , ).
What's more, BCAAs may help reduce the fatigue you feel during exercise by reducing the production of serotonin in your brain ().
Out of the three, leucine is thought have the biggest impact on your body's capacity to build muscle proteins ().
Meanwhile, isoleucine and valine seem more effective at producing energy and regulating your blood sugar levels (, ).
Bottom Line: 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.
Studies in human participants report up to 15% less fatigue in those given BCAAs during exercise, compared to those who were given a placebo (, ).
In one study, this increased resistance to fatigue helped the BCAA group exercise for 17% longer before reaching exhaustion, compared to the placebo group ().
In another study, participants were put under heat stress during a cycling test. They were asked to ingest either a drink containing BCAAs or a placebo. Those who drank the BCAA drink cycled for 12% longer than the placebo group ().
However, not all studies found that decreased fatigue caused improvements in physical performance (, , , , ).
In addition, BCAAs may be more effective at reducing exercise fatigue in untrained compared to trained individuals ().
Bottom Line: 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 ().
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 (, , ).
In some cases, those given BCAAs also performed up to 20% better when they repeated the same strength-training tests 24–48 hours later (, ).
However, effects may vary based on your gender or the total protein content of your diet (, ).
Bottom Line: 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
Many 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 ().
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 (, ).
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 less-expensive 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 ().
Bottom Line: Getting enough BCAAs is likely to 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 (, , ).
However, in practice, not all studies back up these effects (, , ).
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 (, ).
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, one recent study gave participants with liver disease 12.5 grams of BCAAs three times per day. In 10 participants, blood sugar levels were reduced, while 17 participants experienced no effects ().
Therefore, more studies are needed before strong conclusions can be drawn.
Bottom Line: BCAAs may help promote blood sugar control, 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 obese than those consuming an average of 12 grams per day (, ).
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 the 19-day study period ().
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 ().
In another study, weightlifters given 14 grams of BCAAs per day lost 1% more body fat over the eight-week study period than those given 28 grams of whey protein per day. The BCAA group also gained 4.4 lbs (2 kg) more muscle ().
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 ().
Bottom Line: 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 recent review suggests that in patients with liver disease, BCAA supplements may be more beneficial than other supplements at reducing the severity of HE ().
However, BCAAs did not improve overall survival rate, nor did they lower the risk of other complications, such infections and gastric bleeding ().
Another recent 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 ().
BCAA supplements may also be effective at reducing fatigue and improving weakness, sleep quality and muscle cramps in individuals with liver disease ().
In cases of liver cancer, taking BCAA supplements may help reduce water retention and decrease the risk of premature death by up to 7% ().
Bottom Line: BCAA supplements may be effective at improving liver function and decreasing the risk of complications in individuals who have liver disease.
If you'd like to start supplementing with branched-chain amino acids, how much you should take will depend on your individual needs and goals.
A World Health Organization report from 1985 states that the average adult should consume a minimum of 15 mg of BCAAs per pound (34 mg/kg) of body weight each day ().
However, according to more recent research, the daily requirements may actually be as high as 65 mg/lb (144 mg/kg) of body weight per day (, ).
Based on these newer studies, healthy adults should aim to consume:
- Women: A minimum of 9 grams of BCAAs per day
- Men: A minimum of 12 grams of BCAAs per day
People who include sufficient protein-rich foods in their diets most likely do not need to take supplements.
However, daily requirements may be slightly higher for athletes and people doing heavy resistance training. In these cases, supplements may be beneficial.
Most of the studies observing the benefits in trained individuals used supplement doses ranging from 10–20 grams of BCAAs per day.
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.
Bottom Line: Average daily intakes of 5–12 grams of BCAAs are probably sufficient for most people, and can be easily met through diet alone. Athletes may benefit from supplements with 10–20 grams of BCAAs per day.
Top Food Sources
Luckily, there's a large variety of foods that contain BCAAs. Those with the highest amounts include ():
- Meat, poultry and fish: 3–4.5 grams per 3 oz (84 grams)
- Beans and lentils: 2.5–3 grams per cup
- Milk: 2 grams per cup (237 ml)
- Tofu and tempeh: 0.9 to 2.3 grams per 3 oz (84 grams)
- Cheese: 1.4 grams per 1 oz (28 grams)
- Eggs: 1.3 grams per large egg
- Pumpkin seeds: About 1 gram per 1 oz (28 grams)
- Quinoa: 1 gram per cup.
- Nuts: 0.7–1 gram per 1 oz (28 grams), depending on the variety.
Bottom Line: 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.
Studies on the safe upper intake levels of BCAAs are rare, but studies report that total BCAA intakes between 15–35 grams per day seem generally safe (, ).
However, BCAA supplements are not recommended for those suffering from ALS, also known as Lou Gehrig's disease ().
In addition, 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 ().
Bottom Line: BCAA intakes of 15–35 grams per day are considered safe for most people. However, those with ALS or maple syrup urine disease should limit their intakes.
Take Home Message
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.