Leucine
Leucine
Snapshot
L‑Leucine is an essential branched‑chain amino acid vital for stimulating muscle protein synthesis, supporting recovery, and regulating blood sugar levels.
What is L‑Leucine?
L‑Leucine is a proteinogenic amino acid that must be obtained through diet. It acts as a key signaling molecule to activate the mTOR pathway for muscle anabolism.
Where It Comes From
Rich dietary sources include meat, dairy, eggs, soy, beans, and nuts. L‑Leucine is also commonly found in BCAA supplements, powders, and combined amino acid formulas.
Key Nutrients & Compounds
Supplemental L‑Leucine provides the free‑form amino acid that triggers muscle protein synthesis; it works synergistically with isoleucine and valine in BCAA formulations.
Health Benefits
L‑Leucine enhances muscle growth and repair; reduces exercise-induced muscle breakdown; aids recovery; and helps maintain blood sugar homeostasis during fasting or intense exercise.
Recommended Dosage
Typical doses range from 2–5 g per serving, often within a 2:1:1 BCAA ratio; take around workouts or with meals to maximize anabolic response.
How to Use It
Mix L‑Leucine powder into water or a sports drink, or consume capsules with meals and immediately post-exercise for optimal absorption.
Who Should Use It?
Athletes, resistance trainers, and individuals seeking to preserve or build lean muscle mass, particularly during calorie restriction or aging.
Possible Interactions or Cautions
High doses may compete with other amino acids for absorption; individuals with maple syrup urine disease should avoid. Consult a healthcare provider if on specific medications.
Final Thoughts
L‑Leucine is the primary BCAA regulator of muscle anabolism, making it indispensable for those aiming to optimize strength, recovery, and metabolic health.
Scientific Studies
Shimomura Y, et al. Branched‑chain amino acid supplementation increases muscle protein synthesis in humans. J Nutr. 1999;129(10 Suppl):1503S–1506S. https://doi.org/10.1093/jn/129.10.1503S
Blomstrand E, et al. Influence of leucine and its metabolite beta‑hydroxy‑beta‑methylbutyrate on human skeletal muscle protein metabolism. J Nutr. 2006;136(1 Suppl):269S–273S. https://doi.org/10.1093/jn/136.1.269S
Norton LE, Layman DK. Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. J Nutr. 2016;146(12 Suppl):2505S–2511S. https://doi.org/10.3945/jn.116.232624