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.
What this study found
Leucine supplementation increased muscle protein fractional synthetic rate in older adults, suggesting an anabolic effect that may be relevant to sarcopenia. However, pooled evidence showed no significant improvement in lean body mass or leg lean mass, including in longer-term studies. The strongest signal was for short-term muscle protein synthesis rather than clinically measurable changes in body composition.
- Study & population
- Systematic review and meta-analysis of randomized trials in adults aged 65 years or older.
- Intervention
- Oral leucine supplementation was evaluated across trials using both chronic and acute regimens.
- Key limitation
- The evidence came from small trials with heterogeneous populations, doses, durations, and study designs, which limits precision and comparability.
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Open PDFOriginal abstract
In the present study, we performed a meta-analysis to assess the ability of leucine supplementation to increase the muscle protein fraction synthetic rate and to augment lean body mass or leg lean mass in elderly patients. A literature search was conducted on Medline, Cochrane, EMBASE and Google Scholar databases up to 31 December 2013 for clinical trials that investigated the administration of leucine as a nutrient that affects muscle protein metabolism and muscle mass in elderly subjects. The included studies were randomised controlled trials. The primary outcome for the meta-analysis was the protein fractional synthetic rate. Secondary outcomes included lean body mass and leg lean mass. A total of nine studies were included in the meta-analysis. The results showed that the muscle protein fractional synthetic rate after intervention significantly increased in the leucine group compared with the control group (pooled standardised difference in mean changes 1·08, 95% CI 0·50, 1·67; P< 0·001). No difference was found between the groups in relation to lean body mass (pooled standardised difference in mean changes 0·18, 95% CI - 0·18, 0·54; P= 0·318) or leg lean mass (pooled standardised difference in mean changes 0·006, 95% CI - 0·32, 0·44; P= 0·756). These findings suggest that leucine supplementation is useful to address the age-related decline in muscle mass in elderly individuals, as it increases the muscle protein fractional synthetic rate.