Key facts
- One of three branched-chain amino acids (BCAAs).
- The key 'on switch' for muscle protein synthesis.
- Rich in whey, eggs, meat, and dairy.
- Roughly 2–3 g per meal helps maximize the muscle-building signal.
Of the 20 amino acids, leucine stands out for muscle building. It directly activates the mTOR pathway that initiates muscle protein synthesis, effectively telling the body to start building. This is why protein quality — how much leucine a source contains — matters, not just total grams.
Animal proteins like whey, eggs, meat, and dairy are leucine-rich, which is why they're so effective for muscle growth. Getting roughly 2–3 grams of leucine per meal (the amount in a typical protein serving) helps maximize the anabolic signal. Plant-based eaters can hit the same target with larger or combined protein servings.
Frequently asked questions
Why is leucine important for muscle?
Leucine directly activates the cellular pathway that starts muscle protein synthesis, making it the most important amino acid for triggering muscle growth.
Do I need a leucine supplement?
Usually not. A protein-rich diet with quality sources easily provides enough leucine. Supplements are only worth considering if total protein or leucine intake is hard to reach.
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