Overview
Essential BCAA and primary anabolic signaler via mTORC1 activation.
- Whey
- Eggs
- Meat
- L-Leucine
- HMB (metabolite)
Mechanism of action
Activates mTORC1 directly via Sestrin2-GATOR2.
- · mTORC1
Effects on the body
Organ system effects
Threshold leucine ~2.5–3 g per meal optimizes MPS.
Evidence-based benefits
Triggers MPS at ~3 g/meal
Strong evidenceImproves recovery in elderly with low protein intake
Moderate evidencePotential side effects
- · L-Leucine is generally well-tolerated at evidence-based doses
- · Mild GI discomfort (nausea, loose stools, or bloating) possible at higher intakes
- · Headache or transient fatigue reported by a small fraction of users
- · Allergic or hypersensitivity reaction (rash, itching, swelling)
- · Sleep disturbance if taken late in the day
- · Discontinue and seek medical advice if symptoms are severe, persistent, or include difficulty breathing
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 evidence9Show studiesHide studies
L-Leucine: pharmacology, clinical evidence, and safety — narrative review
Examine.com Research Team
Curated narrative review of human and preclinical evidence for L-Leucine, including mechanism, typical dosing, and safety considerations.
Best-supported outcome: Triggers MPS at ~3 g/meal (evidence: strong). Additional outcomes and limitations summarized in the full profile.
PubMed: L-Leucine — Triggers MPS at ~3 g/meal
Live PubMed search
Live results for "L-Leucine Triggers MPS at ~3 g/meal" across the PubMed/MEDLINE peer-reviewed index.
Opens current human and preclinical literature matching L-Leucine and "Triggers MPS at ~3 g/meal". Filter by RCT, meta-analysis, or year on the results page.
PubMed: L-Leucine — Improves recovery in elderly with low protein intake
Live PubMed search
Live results for "L-Leucine Improves recovery in elderly with low protein intake" across the PubMed/MEDLINE peer-reviewed index.
Opens current human and preclinical literature matching L-Leucine and "Improves recovery in elderly with low protein intake". Filter by RCT, meta-analysis, or year on the results page.
PubMed: L-Leucine — randomized controlled trial
Live PubMed search
Live results for "L-Leucine randomized controlled trial" across the PubMed/MEDLINE peer-reviewed index.
Opens current human and preclinical literature matching L-Leucine and "randomized controlled trial". Filter by RCT, meta-analysis, or year on the results page.
PubMed: L-Leucine — meta-analysis
Live PubMed search
Live results for "L-Leucine meta-analysis" across the PubMed/MEDLINE peer-reviewed index.
Opens current human and preclinical literature matching L-Leucine and "meta-analysis". Filter by RCT, meta-analysis, or year on the results page.
PubMed: L-Leucine — pharmacokinetics
Live PubMed search
Live results for "L-Leucine pharmacokinetics" across the PubMed/MEDLINE peer-reviewed index.
Opens current human and preclinical literature matching L-Leucine and "pharmacokinetics". Filter by RCT, meta-analysis, or year on the results page.
PubMed: L-Leucine — safety adverse events
Live PubMed search
Live results for "L-Leucine safety adverse events" across the PubMed/MEDLINE peer-reviewed index.
Opens current human and preclinical literature matching L-Leucine and "safety adverse events". Filter by RCT, meta-analysis, or year on the results page.
PubMed: L-Leucine — dose response
Live PubMed search
Live results for "L-Leucine dose response" across the PubMed/MEDLINE peer-reviewed index.
Opens current human and preclinical literature matching L-Leucine and "dose response". Filter by RCT, meta-analysis, or year on the results page.
Google Scholar: L-Leucine — clinical evidence
Live Scholar search
Cross-database citation index for L-Leucine as it relates to "clinical evidence".
Includes preprints, theses, and journal articles. Useful for tracking citation counts and follow-on work.