From the Guidelines
L-Leucine Overview
L-leucine is a branched-chain amino acid (BCAA) that plays a crucial role in protein synthesis and muscle growth. As a dietary supplement, L-leucine is typically administered in doses ranging from 2-5 grams per day, with some studies suggesting that doses as high as 10 grams per day may be effective for promoting muscle protein synthesis 1.
Key Points About L-Leucine
- Dose and Duration: The recommended duration of L-leucine supplementation varies depending on the individual's goals and health status, but common durations range from 6-12 weeks.
- Medications and Formulations: Medications such as HMB (beta-Hydroxy beta-Methylbutyrate) and other BCAA supplements often contain L-leucine as an active ingredient, with typical formulations containing 2-3 grams of L-leucine per serving.
- Importance in Muscle Protein Synthesis: L-leucine is essential for muscle protein synthesis, and its supplementation has been shown to improve muscle protein synthesis even in the context of inflammation 1.
- Role in Cancer-Related Malnutrition: L-leucine, along with other essential amino acids, may help improve muscle protein synthesis in patients with cancer, potentially mitigating cancer-related malnutrition 1.
Evidence Supporting L-Leucine Use
Studies have indicated that supplementation with L-leucine or high-dose leucine may improve muscle protein synthesis, even within the context of inflammation, although results have not been fully consistent 1. Additionally, L-leucine has been shown to reverse the decrease in disturbed muscle protein homeostasis due to hyperammonaemia 1.
Conclusion is not allowed, so the answer ends here.
From the FDA Drug Label
Metabolism Levacetylleucine is metabolized into acetate and L-leucine by ubiquitously expressed enzymes, which are used endogenously in catabolic and metabolic pathways
- L-leucine is an amino acid that is a product of the metabolism of levacetylleucine. L-leucine is an amino acid. 2
From the Research
Definition of L-leucine
- L-leucine is a nutritionally essential branched-chain amino acid (BCAA) in animal nutrition 3
- It is usually one of the most abundant amino acids in high-quality protein foods 3
- L-leucine is also known as Leu, and it plays a crucial role in protein and energy metabolism 3
Functions of L-leucine
- L-leucine increases protein synthesis through activation of the mammalian target of rapamycin (mTOR) signaling pathway in skeletal muscle, adipose tissue, and placental cells 3
- It promotes energy metabolism, including glucose uptake, mitochondrial biogenesis, and fatty acid oxidation, to provide energy for protein synthesis 3
- L-leucine inhibits protein degradation, and approximately 80% of it is normally used for protein synthesis, while the remainder is converted to α-ketoisocaproate (α-KIC) and β-hydroxy-β-methylbutyrate (HMB) in skeletal muscle 3
Role of L-leucine in Exercise and Sports
- L-leucine supplementation has been suggested to increase protein synthesis, inhibit protein degradation, and regulate energy homeostasis in athletes 4
- Consumption of BCAA, including leucine, before or during endurance exercise may prevent or decrease the net rate of protein degradation and improve mental and physical performance 4
- However, the effects of leucine supplementation on exercise performance are still debated, and further research is needed to fully understand its role 4, 5
Mechanisms of L-leucine Action
- L-leucine activates the mTOR signaling pathway, which regulates translation initiation and protein synthesis 6, 7
- It also increases the expression of L-type amino acid transporter 1 (LAT1), which stimulates amino acid uptake and enhances leucine-induced activation of protein synthesis 6
- The mechanisms underlying the synergistic effects of leucine and exercise on muscle protein synthesis are still being researched 6