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Branched-chain amino acids (BCAAs) are made up of 3 of the 9 essential amino acids:

  • Isoleucine

  • Leucine

  • Valine

While all other amino acids are broken down in the liver, BCAA are metabolized primarily in lean body mass tissue. Because of this, they could help improve exercise performance and also reduce the rate of lean body mass break down.

BCAA supplementation may promote lean body mass protein synthesis and also increase lean body mass in individuals who consume a low protein diet. In one study, leucine and valine were found to cause a significant suppression in body weight loss in mice with cachexia (body-wasting). Both of these BCAA caused a significant increase in muscle tissue, through an increase in protein synthesis and a decrease in degradation


BCAA supplementation may also be effective in preventing fatigue in athletes and physically active people by halting a decline in serum BCAA levels which can occur during physical exertion. A decline in serum BCAA levels typically causes the influx of tryptophan into the brain, which is followed by increased serotonin production - which may result in fatigue.


The amino acid leucine plays a critical role in the synthesis of muscle protein. Isoleucine plays a vital role by inducing cells to store more glycogen. Valine functions synergistically with the other two BCAA, to encourage normal growth, repair bodily tissues, regulate blood sugar levels, and supply the body with energy. Valine also stimulates the central nervous system and is required for healthy mental function.

Isoleucine: Isoleucine is the BCAA best known for its role in increasing endurance, helping to repair lean tissue, and encouraging blood clotting at the site of injury. This BCAA has been shown to provide potential benefit for athletes because its primary role in the body is to increase energy and help recovery from strenuous physical activity.

An isoleucine deficiency can produce symptoms like those of hypoglycemia (low blood sugar), and can include:

  • Headaches

  • Dizziness

  • Fatigue

  • Depression

  • Confusion

  • Irritability


Leucine: Leucine works with the BCAA isoleucine and valine to help repair lean mass, regulate blood sugar, and maintain the body’s energy levels. L-leucine has also shown to temporarily increase the production of growth hormone

Leucine is also an effective BCAA for preventing lean body mass loss because it is metabolized to glucose more quickly than either isoleucine or valine. Increased available glucose inhibits the body having to break down lean body mass for energy during intense exertion.

Leucine is also involved in healing processes in bones, skin, and lean body mass tissue after traumatic injury. Because of this leucine is often administered in nutritional support for people recovering from surgery


Valine: Valine may help in removing excess nitrogen from the liver and in transporting nitrogen to other tissues in the body as required. Valine has also been studied as an adjunctive nutritional support in people with liver and gallbladder disease caused by alcoholism or drug abuse. Valine has also been studied for reversing alcohol-related brain damage.

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