L-Leucine and muscle
What 6 graded rows on l-leucine agree on for muscle, and where they differ. Counted side by side, never averaged.
Consensus finder Rows from the L-Leucine page, reviewed Oct 21, 2026 How it decides
What the rows agree on
Each block and row is one graded row from the L-Leucine page, with its PubMed record.
Your question
L-Leucine and muscle
6 rows · 2,728 peopleMostly no difference: 4 of 6 rows, and most of the people. 2 found an improvement.
- CGrade C× 2
- DGrade D× 4
- Rows
- 6
- Trials
- 16
- At least: a review without a trial count
- People
- 2,728
- Pooled reviews may count some twice
Where they differ
From the rowsThe best-graded row, grade C, is a meta-analysis of 1,418 people (2022) and found no difference.
The 2 rows that found an improvement were larger: a median of 592 people, against a median of 54 people for the 4 rows that found no difference.
Only the 4 rows that found no difference name women and men in their population.
The rows
2 improved · 4 no difference- CGrade CLean mass, handgrip strength and leg press in older adults · No difference
Meta-analysis · n 1,418 · 2022 · Older adults in 17 randomized trials (2009–2022)
Varied by trial · Varied by trial
Leucine on its own did not change total lean mass, handgrip strength or leg press. Combined products containing leucine plus vitamin D improved handgrip strength and gait speed slightly.
- DGrade DLean mass, strength and blood sugar control in older men with type 2 diabetes · No difference
RCT · n 60 · 2011 · Older men with type 2 diabetes, habitual protein intake adequate
2.5 g with each main meal (7.5 g/day) · 6 months
Lean tissue mass, body fat, strength, muscle fibre characteristics, HbA1c and insulin sensitivity did not change or differ from placebo.
- DGrade DMuscle protein synthesis and muscle size during leg immobilization · No difference
RCT · n 48 · 2026 · Recreationally active young (n = 24) and older (n = 24) adults with one leg in a cast
5 g with each main meal (15 g/day) · 3 days
Muscle protein synthesis was about 15–23% lower and thigh muscle area about 1% smaller in the casted leg, with no difference between leucine and placebo.
- DGrade DMuscle synthesis, lean mass, strength and frailty with resistance training · No difference
RCT · n 19 · 2026 · Pre-frail or frail women (mean age 77.5) doing resistance training on a protein-optimized diet (1.2 g/kg/day)
7.5 g/day · 12 weeks
Training raised muscle protein synthesis by 47% and lean mass by 2% and cut frailty criteria by 64%, but leucine added no benefit over placebo.
- CGrade CGrip strength, muscle mass index and gait speed in older adults with sarcopenia · Improved
Meta-analysis, 11 studies · n 1,133 · 2025 · Adults over 65 with sarcopenia (EWGSOP criteria) in 10 randomized trials and 1 prospective study
Varied by trial; a high-dose subgroup was analysed · Varied by trial
Handgrip strength, appendicular muscle mass index and gait speed differed significantly from placebo; the muscle mass difference was also seen in high-dose and leucine-plus-vitamin D subgroups.
- DGrade DSarcopenia measures (walking time, lean mass index) in nursing-home residents · Improved
RCT · n 50 · 2020 · Institutionalised adults aged 65 and over
6 g/day (placebo: 6 g lactose) · 13 weeks
Walking time and lean mass index improved, and maximum expiratory force improved versus placebo; function scales, cognition and inflammatory markers did not change.