Forgot password?

Join NutriDesk


Branched Chain Amino Acids

Branched Chain Amino Acids

What are they?

Amino acids are organic molecules that consist of:

  • a basic amino group (−NH2),
  • an acidic carboxyl group (−COOH), and
  • an organic R group (or side chain) that is unique to each amino acid.

Branched Chain Amino Acids or BCAAs

  • These are L-Leucine, L-Isoleucine and L-Valine
  • They have aliphatic side chains with a carbon atom that is bound to more than two other carbon atoms (a branch).
  • These are amont the 9 essential amino acids which cannot be created in the body but need to be supplied in the diet --- for more information on amino acids in general please click on this link: Amino Acids
  • In humans, the total muscle mass accounts for an estimated 40% of body weight and BCAAs make up nearly a 1/3 of all muscle proteins65.

Unique metabolism

  • BCAAs are metabolized by a group of specific enzymes after absorption.
  • The BCAAs are unique in that they are not broken down in the liver and are transported in the bloodstream directly to skeletal muscle.
  • Once in the muscle, BCAAs enter mitochondria which are the cellular organelles responsible for energy production and are the source of 90% of all energetic output in the human body62.

BCAAs, exercise and muscle growth

  • BCAAs can have powerful effects on protein synthesis. They either decrease the rate of protein breakdown or increase the rate of protein synthesis or both to increase lean muscle mass65.
  • A regulatory protein called mTOR acts like an energy and nutrient sensor.
  • mTOR senses energy availability including caloric intake and helps regulate caloric consumption.
  • mTOR interacts with leptin known as the anoretic hormone as it decreases hunger through signals in the brain.
  • The BCAA L-Leucine was shown to increase mTOR signalling in the hypothalamus of the brain associated with decreased food intake.
  • L-Leucine also interacts with mTOR to stimulate protein synthesis. In aging individuals, the postprandial (after-eating) protein synthesis signals are diminished and adding L-Leucine to the meal can help overcome this problem which is a contributor to sarcopenia or muscle loss in aging26.
  • For a greater understanding of how this mTOR signalling works, see Protein Synthesis

BCAAs and muscle soreness post-exercise

  • It is important to note that 30% of all skeletal muscle protein as mentioned above, is made up of BCAAs.
  • Resistance training works by micro-injuries to muscle fibres which then result in satellite cell activation for repair purposes. Satellite cells are analogous to muscle stem cells. 
  • Without the proper nutritional resources in terms of BCAAs and the other amino acids from protein, tissue repair will be delayed and may even result in ongoing muscle and tendon pain due to poor repair process driven by insufficient nutritional building-blocks.
  • BCAAs used during intense exercise like resistance training, reduced the rise in blood markers of inflammation and muscle damage. The authors of one study stated:

    "These results demonstrate that BCAA supplementation during an intensive training program effectively reduces the muscle soreness and fatigue sensation, and that the perceived changes could be attributed to the attenuation of muscle damage and inflammation.66"
  • Having BCAAs both just before and during resistance training can reduce muscle soreness by 2 - 3 days67. This muscle soreness is simply caused by the damage from exercising. This soreness is also a marker that you have trained intensively enough to cause micro-damage to the muscle which is necessary for muscle growth. But it is also important to ensure that this micro-damage is repaired quickly by having the BCAAs and protein necessary for quick repair.

BCAAs and glycogen stores and recovery

  • An important fact is that BCAAs can delay muscle glycogen depletion and aid muscle glycogen resynthesis65.

BCAAs,  Mitochondrial Biogenesis and Longevity

  • Show to prolong life in the yeast species Saccharomyces cerevisiae64.
  • Increased mitochondrial biogenesis - ie stimulates the formation of new mitochondria63.
  • In mice studies, BCAAs upregulated the expression of SIRT1 gene linked to longevity across a wide range of species.
  • They upregulate genetic defence systems that quench the damaging effects of reactive oxygen species (ROS). that are linked to aging and cellular decay.
  • Exercise acts in a synergistic way with BCAAs to enhance mitochondrial function. Trained mice fed BCAAs had greater numbers of mitochondria in heart and skeletal muscle.
  • The presence of an enzyme involved in blood vessel relaxation (dilation) and blood vessel regulation called endothelial nitric oxide synthase (eNOS) seems to be important in how BCAAs work to improve mitochondrial function and numbers. The BCAA effects are not apparent in mice who lack eNOS63.
  • BCAAs are also involved in the formation of gamma-aminobutyric acid (GABA) the main inhibitory neurotransmitter in the brain and known to regulate neuronal excitability in the human brain. 

BCAAs the Metabolic Syndrome and Diabetes

  • An imporant BCAA, L-Leucine is important in the signalling mechanisms produced by insulin modulating glucose use by skeletal muscle.
  • The Metabolic Syndrome and diabetes can be a muscle wasting process due to insulin resistance and the lost of insulin receptor signals for glucose and amino acid uptake into cells.
  • BCAAs with each meal should be strongly considered along with a high quality protein like whey protein to maximize protein synthesis and glucose uptake and to ensure these pre-diabetic and diabetic individuals maintain and hopefully gain critical lean muscle mass through this disease process.
  • It is important to note that resistance training stimulates all the muscle fibres if done correctly through the orderly recruitment of muscle fibres to reach the important and strongest, Type-IIB muscle fibres and if this is done through quality training guidance, your body responds by increasing the number of GLUT4 insulin receptors which dramatically improve insulin sensitivity and re-establish the important anabolic receptor signals for muscle growth and glucose control.

RDA for L-Leucine

  • It has been suggested that the RDA for L-Leucine should be 45mg/kg/day for sedentary individuals and higher for active individuals65.
  • Whey protein is naturally high in BCAAs65.

Link to QuickGuide Topic References

Please register it's quick and easy.

There is no obligation. Just click on the following link: Join NutriDesk then you can access the references through the link below.

QuickGuide Topic References