L-Leucine
Research reviewed: Up until 03/2026
L-Leucine (L-Leucine (2-amino-4-methylpentanoic acid)) is a dietary supplement with 4 published peer-reviewed studies involving 325 participants, researched for Muscle Protein Synthesis, Muscle Preservation & Anti-Aging.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Muscle Protein Synthesis
ModerateMuscle Preservation & Anti-Aging
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Muscle Protein Synthesis
To evaluate increased protein intake derived from leucine-enriched protein on myofibrillar protein synthesis
Study Type
Randomized, crossover trial
Purpose
To evaluate increased protein intake derived from leucine-enriched protein on myofibrillar protein synthesis
Dose
Leucine-enriched protein bar
Participants
8 young adults
Duration
Short-term acute resistance training
Results
Resistance training increased integrated MyoPS and was significantly enhanced with increased protein intake from leucine-enriched bar.
How They Measured It
Myofibrillar protein synthesis (MyoPS), protein signaling
To compare native whey protein high in leucine with regular whey protein for post-exercise muscle protein synthesis
Study Type
Randomized, controlled trial
Purpose
To compare native whey protein high in leucine with regular whey protein for post-exercise muscle protein synthesis
Dose
Native whey protein vs regular WPC-80
Participants
24 young resistance-trained men and women
Duration
Post-exercise measurement
Results
Despite larger increase in blood leucine with native whey, both stimulated post-exercise p70S6K-phosphorylation and MPS similarly.
How They Measured It
Muscle protein synthesis rate, phosphorylation of p70S6K
Muscle Preservation & Anti-Aging
To evaluate effects of leucine-enriched high protein supplementation on body composition and muscle function in older adults with sarcopenia
Study Type
Randomized, controlled trial
Purpose
To evaluate effects of leucine-enriched high protein supplementation on body composition and muscle function in older adults with sarcopenia
Dose
Leucine-enriched whey protein supplement
Participants
Older adults with sarcopenia
Duration
12-24 weeks
Results
Leucine-enriched high protein supplementation more effective than placebo at improving muscle mass, strength, and function in older adults.
How They Measured It
Muscle mass, strength, physical function
To evaluate effects of free leucine supplementation and resistance training on muscle strength and functional status in older adults
Study Type
Randomized, controlled trial
Purpose
To evaluate effects of free leucine supplementation and resistance training on muscle strength and functional status in older adults
Dose
Free leucine supplementation
Participants
Older adults
Duration
12 weeks
Results
Free leucine combined with resistance training showed beneficial effects on muscle strength and functional status in older adults.
How They Measured It
Muscle strength, physical function, body composition
Frequently Asked Questions
Common questions about L-Leucine research
There are currently 6 peer-reviewed studies on L-Leucine (L-Leucine (2-amino-4-methylpentanoic acid)), involving 325 total participants. Research covers Muscle protein synthesis, Muscle preservation, Athletic performance. The overall evidence strength is rated as Moderate.
The evidence is currently rated as "Moderate Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (4 human studies), and reported outcomes.
L-Leucine has been researched for: Muscle protein synthesis, Muscle preservation, Athletic performance. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 4 out of 6 studies are human trials. Human trials carry more weight in our evidence scoring system.
