Overview
Branched-chain amino acid that triggers mTOR.
- Dietary protein from animal sources (meat, fish, eggs, dairy) and plant sources (soy, legumes, grains)
- Free-form amino acid powders and capsules
- Targeted pre-workout, recovery, or sleep formulations
- Free-form crystalline powder
- Capsules or tablets
- Pre-mixed recovery or hydration beverages
- Time-release formulations
Mechanism of action
Activates mTORC1 to stimulate muscle protein synthesis.
- · Activates mTORC1 to stimulate muscle protein synthesis
Effects on the body
Organ system effects
L-Leucine influences muscle protein synthesis, neuromuscular output, or recovery from exercise.
Evidence-based benefits
Stimulates MPS
Moderate evidencePotential side effects
- · GI upset
Drug interactions
Supplement interactions
- Creatine monohydrateFoundational support for strength, power, and lean mass.
- Whey or EAAsProvides amino acid substrate for muscle protein synthesis.
No specific avoidances listed.
Dosing & bioavailability
Where to buy
Affiliate links — we may earn a commission at no extra cost to you. Amazon code supplementsch-20 is auto-applied at checkout. We don't endorse specific brands; verify third-party testing (USP, NSF, Informed Sport) before purchase.
Third-party testedIndependently verified L-Leucine — look for USP, NSF, or Informed Sport seals on the label for purity and dose accuracy.L-Leucine third party tested NSF
CapsulesPre-measured L-Leucine capsules — easiest for travel and consistent daily dosing without scoops or scales.L-Leucine capsules
PowderBulk unflavored L-Leucine powder — best cost-per-gram and flexible dosing for stacking or mixing into drinks.L-Leucine powder unflavored
Best sellersMost-purchased L-Leucine products on Amazon — a quick way to see what's reviewed widely before you commit.L-Leucine best sellerScientific evidence8Show studiesHide studies
Leucine and MPS in elderly
Katsanos CS, et al.
Elderly given EAA
Leucine-enriched EAA stimulated MPS.
PubMed: L-Leucine — Stimulates MPS
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PubMed: L-Leucine — randomized controlled trial
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PubMed: L-Leucine — meta-analysis
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PubMed: L-Leucine — pharmacokinetics
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PubMed: L-Leucine — safety adverse events
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PubMed: L-Leucine — dose response
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Google Scholar: L-Leucine — clinical evidence
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