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Branched-Chain Amino Acids (BCAA)

What are Branched-Chain Amino Acids (BCAAs)?

BCAAs, which include leucine, isoleucine and valine, are essential amino acids, you have to obtain from food because your body cannot produce them. The name “branched” refers to the typical structure of the BCAAs molecule.

BCAAs Functions

  • A source of energy; BCAAs provide 4 Calories per gram of energy, just like proteins
  • Stimulation of protein synthesis, especially in muscles, and promotion of muscle repair
  • Production of glutamate, an excitatory neurotransmitter in the brain
  • Reference: [1]

Foods High in BCAAs

Amount of BCAAs in prepared foods:

  • PLANT FOODS: beans (2 g/cup); pumpkin seeds (1.5 g/oz); nuts (1 g/oz); quinoa (1 g/cup)
  • ANIMAL FOODS: milk, nonfat (10 g/cup); cheese (5 g/100 g); chicken, turkey, pork, beef, fish (4 g/3 oz); egg (1 g/egg)
  • Breast milk: 2 g/liter

NOTE: Whey (powder) is relatively low in BCAAs (~0,5 g/oz)

BCAAs are not destroyed by heating, just like amino acids in meat are not destroyed by cooking.

Reference: US Department of Agriculture [10]

One 2013 study in Japan has suggested that high dietary intake of BCAAs could decrease the risk of diabetes 2 [9].

BCAAs Deficiency Symptoms

Deficiency of BCAAs usually occurs along with protein malnutrition. Deficiency of BCAAs alone is rare and may occur in individuals with chronic kidney failure and liver cirrhosis [13]. The main symptom is anorexia (poor appetite) [3].

BCAAs Supplements

BCAAs supplements are available as tablets, capsules, powder, drink and a solution for intravenous injection. They can be included in “protein powder” products or combined with creatine, glutamine or other amino acids.

BCAAs in supplements are in the free-form, which means they are not linked with each other like in proteins, so they do not need to be digested and can appear in the blood ad muscles much quicker than BCAAs from foods [12].

Can BCAAs supplements be good for you?

BCAAs supplements are POSSIBLY EFFECTIVE in:

  • Reducing anorexia (poor appetite) in individuals on kidney hemodialysis or having cancer
  • Decreasing symptoms of mania within several hours to few weeks
  • Reducing muscle breakdown and soreness during exercise [1,4]
  • Reducing involuntary facial movements (tardive dyskinesia) in children and adults who take antipsychotic drugs.

The main reference: Natural Medicines Comprehensive Database [1]

There is INSUFFICIENT EVIDENCE about the effectiveness of BCAAs supplements in reducing fatigue, improving concentration, in the treatment of diabetes 2 and spinocerebellar degeneration [1], promoting weight loss or fat loss [6,7] or treatment of hepatic encephalopathy (brain disorder in individuals with severe liver disease, mainly in alcoholics) [8] .

BCAAs supplements are POSSIBLY INEFFECTIVE in enhancing athletic performance [11], treatment of amyotrophic lateral sclerosis (ALS) [1] or treatment of muscle recovery after prolonged bed rest [5].


  • For chronic hepatic encephalopathy, tablets up to 25 grams per day, or intravenous injection of a BCAA solution, 80-120 g/day
  • For mania, a drink with a BCAA mixture, 60 grams for 7 days
  • For anorexia during hemodialysis, BCAA granules, 3 x 4 g/day
  • Reference [1]


Bodybuilders and runners often use BCAAs. Sport doctors often recommend taking BCAAs pre- and post- workout to enable optimal muscle regeneration [11]. Again, several reviews have shown that BCAAs do not increase athletic performance [1,11].

BCAAs Safety: Side Effects, Toxicity

BCAAs supplements appear to be safe to use in children and adults according to studies lasting for up to 6 months. Side effects may include fatigue, nausea and muscle incoordination [1].

Allergic reactions to BCAAs supplements are possible but would be much more likely caused by added substances than BCAAs themselves.

Safety During Pregnancy and Breastfeeding

Pregnant and breastfeeding women should avoid BCAAs supplements since their safety during these periods has not been studied well [1].

Who else should avoid BCAAs supplements?

  • Anyone drinking a lot of alcohol; BCAAs triggered hepatic encephalopathy in one case [1]
  • Individuals with amyotrophic lateral sclerosis (ALS, Lou Gehrig’s disease)
  • Individuals with  branched-chain keto aciduria, also known as maple syrup urine disease (MSUD); they should also have a low-BCAAs diet [2]
  • Infants with idiopathic hypoglycemia
  • Individuals scheduled for surgery in the next two weeks
  • Main reference: [1]

BCAAs-Drugs Interactions

BCAAs supplements may [1]:

  • Decrease absorption of levodopa
  • Increase the glucose-lowering effect of anti-diabetic drugs, such as glipizide and insulin.

Maple Syrup Urine Disease (MSUD)

Maple syrup urine disease (MSUD) is a rare genetic disease with an inability to break down branched-chain amino acids (BCAAs) leucine, isoleucine and valine due to a lack of appropriate enzymes, so they accumulate in the blood and may affect the brain and other organs [14].

Symptoms, which develop from the 4th day to the second week after birth, include maple syrup smelling urine, poor appetite, vomiting and lethargy [14]. Mild and severe forms of the disease exist. If untreated, seizures, coma or death may occur. Brain damage can result in mental retardation. Blood tests show increased levels of leucine, isoleucine and valine, and the presence of alloisoleucine. There is no treatment; symptoms can be prevented by a life-long diet low in leucine, isoleucine and valine. With a strict diet, children may survive until adulthood.

  1. Branched-chain amino acids supplements information, effects  Natural Medicines Comprehensive Database
  2. Maple syrup urine disease diet  Emedicine
  3. BCAAs in kidney failure  Journal of Nutrition
  4. BCAAs effect of muscle soreness after exercise  PubMed
  5. BCAAs and muscle recovery after prolonged bed rest  Journal of Applied Physiology
  6. BCAAS and abdominal fat loss  PubMed
  7. BCAAs associated with lower obesity prevalence  PubMed Central
  8. The beneficial effect of BCAAs in hepatic encephalopathy  Cochrane Summaries
  9. BCAAS intake and diabetes  PubMed
  10. Natural sources of BCAAs  US Department of Agriculture
  11. BCAAs enhance muscle recovery but not athletic performance  Pubmed
  12. Almeida CC et al, 2016, Protein and Amino Acid Profiles of Different Whey Protein Supplements  PubMed
  13. BCAAs deficiency in liver cirrhosis  PubMed
  14. Maple syrup urine disease, clinical presentation  Emedicine

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