Branched-Chain Amino Acids (BCAA) consists of three amino acids, including leucine, isoleucine, and valine.
These essential amino acids have branched molecular structures and can not be synthesized in higher organisms.
Key Health Benefits of BCAAs
The key benefits of BCAA include reducing fatigue, muscle soreness, and increasing lean mass in trained athletes. It had a beneficial effect in improving the quality of life in patients with liver cirrhosis. It may also play a role in improving sleep disturbances and reducing body fat.
1. BCAAs increase improves the quality of life in liver cirrhosis patients
BCAA administration increases serum albumin levels, thereby improves the quality of life and prognosis in patients with liver cirrhosis.
Patients with cirrhosis have protein deficiencies, which could lead to hypoalbuminemia, thereby reducing their quality of life. 
A multicenter randomized trial showed that BCAA supplementation (12g/day) in decompensated cirrhosis patients for two years increased serum albumin concentration and improved their quality of life. 
In a study with Japanese liver cirrhosis patients, 48 weeks of BCAA supplementation decreased fat accumulation, enhanced glucose sensitivity, and improved the survival of liver cirrhosis patients.
In 16 randomized clinical trials, BCCA supplements had a beneficial effect on the symptoms of hepatic encephalopathy, a complication of cirrhosis.
What it means: BCCA supplementation for a long time increased serum albumin concentration, which improved the quality of life in patients with decompensated cirrhosis. It may also have a beneficial effect on hepatic encephalopathy. Future large scale studies are needed to determine the sufficient dosage needed to increase these beneficial effects.
2. BCAAs may reduce central fatigue during endurance exercise
BCCA supplements may reduce fatigue during exercise.
During prolonged exercise, there is an increased influx of tryptophan, which leads to increased production of the neurotransmitter, serotonin, causing central fatigue.
BCCA supplements inhibit tryptophan transport, lower serotonin, and thereby may decrease central fatigue.
When seven male cyclists were supplemented with BCAAs during exercise, their ratings for perceived exertion were 7% lower, and mental fatigue ratings were 15% lower compared to placebo.
However, there was no difference in physical performance between the two groups. 
In another study, subjects were supplemented with BCAAs (300mg/day) for three days and then completed an exercise trial. They showed a 17.2 % greater resistance to fatigue.
What it means: The studies showed that BCCA supplementation may reduce central fatigue associated with exercise. More studies are required to determine the BCAA dosage required for reducing fatigue after different forms of exercise.
3. BCAAs may reduce exercise-induced delayed onset muscular soreness (DOMS)
The studies showed that BCCA supplementation may reduce muscle soreness during recovery from intense exercise.
BCAAs may decrease the serum concentration of intramuscular enzymes including, creatine kinase and lactate dehydrogenase, and thereby reduce muscle soreness.
These enzymes are the indicators of muscle damage after the exercise, 
In a meta-analysis involving eight randomized clinical trials, BCCA supplementation caused a reduction in muscle soreness and improved muscle function. 
In another study, a combination of 3.2g BCAA and 2g taurine two weeks prior and three days after exercise reduced DOMS and muscle damage. 
What it means: DOMS occurs after exercise. BCCA supplementation may reduce muscle soreness following exercise, which may help in speeding up the recovery. Further studies are required to elucidate optimal dose, markers involved, and ingestion periods.
4. BCAAs may improve the lean muscle mass
The studies showed that BCCA supplementation may help in improving lean muscle mass and lose body fat.
In a randomized double-blind study, intake of BCAA supplement (14g) following eight-week resistance training resulted in an increase in lean muscle mass and a decrease in body fat.
In a clinical trial, BCCA supplementation improved lean muscle mass in people with rheumatoid arthritis.
In another study with 68 patients, the eight-week intervention of BCAAs improved muscle mass and hand-grip strength in sarcopenia adults.
What it means: BCAAs may improve lean muscle mass and reduce body fat in athletes. It may increase lean muscle mass in older adults with arthritis and sarcopenia. However, the results are inconclusive because of the variability in experimental procedures, supplement dosage, treatment duration, and dietary control.
5. BCAAs may help in improving hepatic function in liver cancer patients
BCAA supplementation may have a role in improving hepatic functions, and decreasing the rate of therapy interruption in patients with hepatocellular carcinoma (HCC).
The patients with HCC have low serum albumin levels causing edema, which in turn interferes with anticancer therapy.
In a study involving 124 patients who had undergone hepatectomy due to cancer, intravenous nutritional support with BCCA supplement reduced postoperative morbidity.
In a meta-analysis study, BCCA supplements improved serum albumin levels, reduced risk of complication, and duration of stay in patients undergoing the hepatic operation.
What it means: BCAA supplementation increases serum albumin level and thereby may improve hepatic functions, and quality of life in patients with hepatocellular carcinoma after hepatic resection. More research studies are required to elucidate the effects of BCAA supplements in inhibiting the proliferation of liver cancer cells and reducing the mortality of liver cancer patients.
6. BCAAs may help in reducing body fat
The studies showed that BCCA supplementation may help in reducing the percentage of body fat.
In a study with northern Chinese adults, higher BCAA intake reduced the prevalence of obesity.
A similar effect was observed in middle-aged East Asian and Western adults.
In another study, twenty-five wrestlers consuming calorie-restricted diet supplemented with BCCAs over the 19 day study period showed a significant reduction in abdominal visceral adipose tissue.
What it means: BCAAs may help in reducing body fat and prevent weight gain. Further long term cohort studies are needed to explore the potential mechanism and determine whether BCAAs provide any benefits over a high protein diet.
7. BCAAs may help in improving sleep disturbances
Some studies show that BCCA supplements at night may improve sleep disturbances and respiratory controls during sleep.
In one study with five healthy individuals, nocturnal BCAA infusion improved respiratory controls during sleep and thus may help in reducing sleep apnea. 
In another study, chronic renal patients had reduced sleep quality and decreased amount of rapid eye movement. BCAA infusion in such patients increased REM sleep and decreased end-tidal CO2, which in turn improved respiratory function during sleep.
What it means: Preliminary research shows that BCAA supplements may be effective in improving sleep disturbances. However, larger clinical trials are needed to confirm the preliminary research.
BCAA are generally safe when given orally or injected intravenously by a healthcare professional. It can sometimes cause stomach problems, nausea, vomiting, and loss of coordination.
It may cause high blood pressure or skin whitening in rare cases.
Avoid using BCAAs during pregnancy and lactating as there is not enough information about its safety during pregnancy.
It is safe in children when used for short term (6 months). Avoid using BCAAs when the person has amylotrophic lateral sclerosis (ALS), ketoaciduria, chronic alcoholism.
Also, stop using BCAAs before surgery as it might affect sugar levels.
BCAAs might interact with medications for diabetes, corticosteroids, Parkinson’s disease inflammation, and thyroid hormones. Always consult a healthcare practitioner before taking BCAAs.
There is no recommended dose of BCAA. The recommended dose of isoleucine is 48-72mg/kg.
Leucine is supplemented in the range of 2-10g. Most of the studies used BCAAs ranging from 10-20gm per day.
BCAAs are essential amino acids that can not be synthesized in the body.
So, there BCAAs are obtained either from diet or supplements. Research suggests that BCAA supplements may improve muscle soreness, fatigue, and increase lean mass in athletes. It may improve the quality of life in liver cirrhosis patients.
However, some research linking it to reducing the risk of cancer and improving sleep disturbances are yet to be established.
Therefore, future studies are required to fill up the gap between BCAAs and their metabolic functions.