SYS ONLINE
SUPPLEMENT_SCHOLAR
evidence · mechanism · dose
Supplements/Amino Acid

L-Leucine

Essential BCAA and primary anabolic signaler via mTORC1 activation.

Muscle GrowthAthletic Performance

Overview

Essential BCAA and primary anabolic signaler via mTORC1 activation.

Natural sources
  • Whey
  • Eggs
  • Meat
Common forms
  • L-Leucine
  • HMB (metabolite)

Mechanism of action

Activates mTORC1 directly via Sestrin2-GATOR2.

Pathways
  • · mTORC1

Effects on the body

Supports
Muscle protein synthesis

Organ system effects

Skeletal Muscle

Threshold leucine ~2.5–3 g per meal optimizes MPS.

Evidence-based benefits

Triggers MPS at ~3 g/meal

Strong evidence

Improves recovery in elderly with low protein intake

Moderate evidence

Potential side effects

Common
    Rare
      Serious

        Drug interactions

        No notable interactions reported.

        Supplement interactions

        Pairs well with

        None listed.

        Avoid combining with

        No specific avoidances listed.

        Dosing & bioavailability

        Typical dose
        2.5–5 g per dose; 3 g optimal MPS trigger

        Where to buy

        Affiliate-style search links to reputable retailers. We don't endorse specific brands — verify third-party testing (USP, NSF, Informed Sport) before purchase.

        Amino Acid
        L-Leucine
        Amazon
        Wide selection · fast shipping
        Amino Acid
        L-Leucine
        iHerb
        Global delivery · curated brands
        Amino Acid
        L-Leucine
        Thorne
        Practitioner-grade · NSF tested

        Scientific evidence (9)

        Systematic reviewExamine.com Supplement Database · 2023

        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.

        Key findings

        Best-supported outcome: Triggers MPS at ~3 g/meal (evidence: strong). Additional outcomes and limitations summarized in the full profile.

        Open study
        Systematic reviewPubMed (NLM) · 1970

        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.

        Key findings

        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.

        Open study
        Systematic reviewPubMed (NLM) · 1970

        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.

        Key findings

        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.

        Open study
        Systematic reviewPubMed (NLM) · 1970

        PubMed: L-Leucine — randomized controlled trial

        Live PubMed search

        Live results for "L-Leucine randomized controlled trial" across the PubMed/MEDLINE peer-reviewed index.

        Key findings

        Opens current human and preclinical literature matching L-Leucine and "randomized controlled trial". Filter by RCT, meta-analysis, or year on the results page.

        Open study
        Systematic reviewPubMed (NLM) · 1970

        PubMed: L-Leucine — meta-analysis

        Live PubMed search

        Live results for "L-Leucine meta-analysis" across the PubMed/MEDLINE peer-reviewed index.

        Key findings

        Opens current human and preclinical literature matching L-Leucine and "meta-analysis". Filter by RCT, meta-analysis, or year on the results page.

        Open study
        Systematic reviewPubMed (NLM) · 1970

        PubMed: L-Leucine — pharmacokinetics

        Live PubMed search

        Live results for "L-Leucine pharmacokinetics" across the PubMed/MEDLINE peer-reviewed index.

        Key findings

        Opens current human and preclinical literature matching L-Leucine and "pharmacokinetics". Filter by RCT, meta-analysis, or year on the results page.

        Open study
        Systematic reviewPubMed (NLM) · 1970

        PubMed: L-Leucine — safety adverse events

        Live PubMed search

        Live results for "L-Leucine safety adverse events" across the PubMed/MEDLINE peer-reviewed index.

        Key findings

        Opens current human and preclinical literature matching L-Leucine and "safety adverse events". Filter by RCT, meta-analysis, or year on the results page.

        Open study
        Systematic reviewPubMed (NLM) · 1970

        PubMed: L-Leucine — dose response

        Live PubMed search

        Live results for "L-Leucine dose response" across the PubMed/MEDLINE peer-reviewed index.

        Key findings

        Opens current human and preclinical literature matching L-Leucine and "dose response". Filter by RCT, meta-analysis, or year on the results page.

        Open study
        Systematic reviewGoogle Scholar · 1970

        Google Scholar: L-Leucine — clinical evidence

        Live Scholar search

        Cross-database citation index for L-Leucine as it relates to "clinical evidence".

        Key findings

        Includes preprints, theses, and journal articles. Useful for tracking citation counts and follow-on work.

        Open study
        Educational use only. This profile is not medical advice. Consult a qualified healthcare professional before starting any supplement, especially if you take prescription medication or have a chronic condition.