Why is Leucine more important?
Although other amino acids have key roles in building muscle the impact of leucine is stated as being many times more potent than any others, so how does it do this? The exact action by which Leucine increases muscle building is complex in nature, but fundamentally it proposed to work by stimulating a pathway that regulates muscle cell growth through the mammalian target of rapamycin (mTOR) a protein in muscle cells.
This pathway instructs the muscle cells to use the amino acids, growth factors and energy sources available to build muscle, Leucine appears to be a key mediator in signalling these complex pathways to maintain optimum muscle protein synthesis. Leucine supplementation comes most commonly in its L-Leucine form (usually in combination with Isoleucine and Valine and/or other BCAAs), optimum Leucine dosing to maintain muscle protein synthesis has been cited as being around 2 to 5g of Leucine every 4 to 6 hours, dosages above this do not appear to have increased benefit in terms of muscle protein synthesis.
Leucine is best used in combination with other BCAA’s to optimise its effects, Leucine is found from many food sources, 20g of whey protein contains around 3g of Leucine with a similar amount being found in approximately 180g of chicken or 150g of beef. BCAA supplements are increasingly popular taken intra-workout where food and shakes are not easily consumed. The primary advantage of a high-quality BCAA supplement is its very fast acting digestion and absorption rates, ensuring that the muscle cells remain in a fed state preventing an excessive breakdown of muscle tissue and increased recovery times.
Leucine is commonly used in either on its own or as an addition to food protein sources, as it increases the uptake of the amino acids helping maintain muscle tissue when in calorific deficit during dieting/fasting or when a need for optimum recovery is required to handle high training volumes or loads.