One of the most popular uses of BCAAs is to increase muscle growth.

The BCAA leucine activates a certain pathway in the body that stimulates muscle protein synthesis, which is the process of making muscle (1, 2).

In one study, people who consumed a drink with 5.6 grams of BCAAs after their resistance workout had a 22% greater increase in muscle protein synthesis compared to those who consumed a placebo drink (3).

That being said, this increase in muscle protein synthesis is approximately 50% less than what was observed in other studies where people consumed a whey protein shake containing a similar amount of BCAAs (4, 5).

Whey protein contains all the essential amino acids needed to build muscle.

Therefore, while BCAAs can increase muscle protein synthesis, they can’t do so maximally without the other essential amino acids, such as those found in whey protein or other complete protein sources (6, 7).

SUMMARY

BCAAs play an important role in building muscle. However, your muscles require all the essential amino acids for the best results.

Some research suggests BCAAs can help decrease muscle soreness after a workout.

It’s not uncommon to feel sore a day or two after a workout, especially if your exercise routine is new.

This soreness is called delayed onset muscle soreness (DOMS), which develops 12 to 24 hours after exercise and can last up to 72 hours (8).

While the exact cause of DOMS is not clearly understood, researchers believe it’s the result of tiny tears in the muscles after exercise (9, 10).

BCAAs have been shown to decrease muscle damage, which may help reduce the length and severity of DOMS.

Several studies show that BCAAs decrease protein breakdown during exercise and decrease levels of creatine kinase, which is an indicator of muscle damage (11, 12, 13)

In one study, people who supplemented with BCAAs before a squat exercise experienced reduced DOMS and muscle fatigue compared to the placebo group (14).

Therefore, supplementing with BCAAs, especially before exercise, may speed up recovery time (15, 16).

SUMMARY

Supplementing with BCAAs may decrease muscle soreness by reducing damage in exercised muscles.

Just as BCAAs may help decrease muscle soreness from exercise, they may also help reduce exercise-induced fatigue.

Everyone experiences fatigue and exhaustion from exercise at some point. How quickly you tire depends on several factors, including exercise intensity and duration, environmental conditions and your nutrition and fitness level (17).

Your muscles use BCAAs during exercise, causing levels in your blood to decrease. When blood levels of BCAAs decline, levels of the essential amino acid tryptophan in your brain increase (18).

In your brain, tryptophan is converted to serotonin, a brain chemical that is thought to contribute to the development of fatigue during exercise (19, 20, 21).

In two studies, participants who supplemented with BCAAs improved their mental focus during exercise, which is thought to result from the fatigue-reducing effect of BCAAs (22, 23).

However, this decrease in fatigue is unlikely to translate to improvements in exercise performance (24, 25).

SUMMARY

BCAAs may be useful in decreasing exercise-induced fatigue, but they are unlikely to improve exercise performance.

BCAAs can help prevent muscle wasting or breakdown.

Muscle proteins are constantly broken down and rebuilt (synthesized). The balance between muscle protein breakdown and synthesis determines the amount of protein in muscle (26).

Muscle wasting or breakdown occurs when protein breakdown exceeds muscle protein synthesis.

Muscle wasting is a sign of malnutrition and occurs with chronic infections, cancer, periods of fasting and as a natural part of the aging process (27).

In humans, BCAAs account for 35% of the essential amino acids found in muscle proteins. They account for 40% of the total amino acids required by your body (28).

Therefore, it’s important that the BCAAs and other essential amino acids are replaced during times of muscle wasting to halt it or to slow its progression.

Several studies support the use of BCAA supplements for inhibiting muscle protein breakdown. This may improve health outcomes and quality of living in certain populations, such as the elderly and those with wasting diseases like cancer (29, 30, 31).

SUMMARY

Taking BCAA supplements can prevent the breakdown of protein in certain populations with muscle wasting.

BCAAs may improve health in people with cirrhosis, a chronic disease in which the liver does not function properly.

It’s estimated that 50% of people with cirrhosis will develop hepatic encephalopathy, which is the loss of brain function that occurs when the liver is unable to remove toxins from the blood (32).

While certain sugars and antibiotics are the mainstays of treatment for hepatic encephalopathy, BCAAs may also benefit people suffering from the disease (33, 34).

One review of 16 studies including 827 people with hepatic encephalopathy found that taking BCAA supplements had a beneficial effect on the symptoms and signs of the disease, but had no effect on mortality (35).

Liver cirrhosis is also a major risk factor for the development of hepatocellular carcinoma, the most common form of liver cancer, for which BCAA supplements may also be useful (36, 37).

Several studies have shown that taking BCAA supplements may offer protection against liver cancer in people with liver cirrhosis (38, 39).

As such, scientific authorities recommend these supplements as a nutritional intervention for liver disease to prevent complications (40, 41).

SUMMARY

BCAA supplements may improve the health outcomes of people with liver disease, while also possibly protecting against liver cancer.

BCAAs are found in foods and whole protein supplements.

Getting BCAAs from complete protein sources is more beneficial, as they contain all the essential amino acids.

Fortunately, BCAAs are abundantly found in many foods and whole protein supplements. This makes BCAA supplements unnecessary for most, especially if you consume enough protein in your diet already (42).

Consuming protein-rich foods will also provide you with other important nutrients that BCAA supplements lack.

The best food sources of BCAAs include (43):

SUMMARY

Many protein-rich foods contain high amounts of BCAAs. If you consume enough protein in your diet, BCAA supplements are unlikely to provide additional benefits.

The branched-chain amino acids (BCAAs) are a group of three essential amino acids: leucine, isoleucine and valine.

They are essential, meaning they can’t be produced by your body and must be obtained from food.

BCAA supplements have been shown to build muscle, decrease muscle fatigue and alleviate muscle soreness.

They have also successfully been used in a hospital setting to prevent or slow muscle loss and to improve symptoms of liver disease.

However, because most people get plenty of BCAAs through their diet, supplementing with BCAA is unlikely to provide additional benefits.