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Leu4.5

Leucine Research

4 peer-reviewed studies

Our research database did not respond in time, so this list covers only our curated studies. It refreshes automatically.

What the evidence says

Mostly mechanism / observational

Most Leucine studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.

Most evidence is from high-quality meta-analyses and randomised trials published 2009–2025 with a typical study size of 302 participants.

Based on 4 studies · 3 meta-analyses · 1 RCT · 302 total participants

Confidence

High confidence

By outcome

Lean body mass & muscle growthUncertain. Leucine triggers the muscle protein synthesis response, but the long-term RCT verified for this entry found no increase in muscle mass or strength in healthy elderly men taking it on top of a normal diet. Mapped at a low relevance deliberately. · Not established here
Mostly mechanism / observational3 studies
Muscle strength & powerUncertain. Leucine triggers the muscle protein synthesis response, but the long-term RCT verified for this entry found no increase in muscle mass or strength in healthy elderly men taking it on top of a normal diet. Mapped at a low relevance deliberately. · Not established here
Too few graded studies2 studies
Therapeutic & clinical
Too few graded studies2 studies

Steady research

1 study in the last 5 years · Latest meta-analysis: 2025

200920172025

1Total body mass change during resistance exercise trainingMeta-AnalysisCited 19×n=302 · medium study2020

In plain English: Our findings do not support the use of HMB aiming at improvement of body composition or strength with RET.

Jakubowski JS et al. · Nutrients (2020)

A significant effect was found on TBM.
However, there were no significant effects for FFM, FM, or strength outcomes.
We conclude that HMB produces a small effect on TBM gain, but this effect does not translate into significantly greater increases in FFM, strength or decreases in FM during periods of RET.

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2RCTCited 192×2009

In plain English: The paper's own title states the result: long-term leucine supplementation does not increase muscle mass or strength in healthy elderly men.

Verhoeven S et al. · Am J Clin Nutr (2009)

Randomised controlled trial of long-term leucine supplementation in healthy elderly men (PubMed publication types: Randomized Controlled Trial)
The result is stated in the title itself — no increase in muscle mass or strength — so it is grounded without reading the abstract
This is the counter-evidence the entry is built around, and the reason its evidence score sits below 5

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3Meta-AnalysisCited 103×2015

In plain English: The first systematic review and meta-analysis of leucine specifically, pooling muscle protein synthesis, lean body mass and leg lean mass accretion in older people.

Xu ZR et al. · Br J Nutr (2015)

Systematic review and meta-analysis of leucine in older people (PubMed publication types: Meta-Analysis, Systematic Review)
Pools three distinct outcomes — muscle protein synthesis, lean body mass and leg lean mass accretion — rather than a single endpoint
Cited as a top-of-pyramid synthesis for the sarcopenia indication

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4Meta-AnalysisCited 5×2025

In plain English: The most recent meta-analysis of leucine supplementation in older adults with sarcopenia identified for this entry.

Hsieh MH et al. · Nutrients (2025)

Meta-analysis of leucine supplementation in older adults with sarcopenia (PubMed publication types: Meta-Analysis, Review)
Included as the most recent synthesis, so the entry is not anchored only on the 2015 reviews
Restricted to older adults who already have sarcopenia, which is a narrower population than healthy older adults

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View in Research Library

Leucine Research

Mostly mechanism / observational

Supplementation with the Leucine Metabolite β-hydroxy-β-methylbutyrate (HMB) does not Improve Resistance Exercise-Induced Changes in Body Composition or Strength in Young Subjects: A Systematic Review and Meta-Analysis

Long-term leucine supplementation does not increase muscle mass or strength in healthy elderly men.

The effectiveness of leucine on muscle protein synthesis, lean body mass and leg lean mass accretion in older people: a systematic review and meta-analysis.

Effects of Leucine Supplementation in Older Adults with Sarcopenia: A Meta-Analysis.