The Study
Effects of leucine intake on muscle growth, strength, and recovery in young active adults: a systematic review of randomized controlled trials
This study looked at lots of experiments where people took leucine pills or drinks and trained with weights. It found that, on average, the leucine didn’t help them get bigger, stronger, or recover faster than people who took fake pills. So we can say: if you’re a healthy young person who already trains, leucine probably won’t help you more than your regular diet.
Analysis score
Maximum 100 for a systematic review.
Where the score came from
Leucine is a protein building block that tricks muscles into thinking it's time to grow, but when you already eat enough protein, taking extra leucine pills doesn't help.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 520 / 100
Quality score
Systematic reviews and meta-analyses of cohort studies. They sit above a single cohort study but below a single randomized trial, because the underlying evidence is still observational.
Key takeaways
Summary
Based on the study abstract and findings.
- 1No, the result is not significant for a human — taking leucine supplements won't help you get bigger or stronger if you're already eating enough protein.
- 213 out of 14 studies found no difference between leucine and placebo groups in muscle gain, strength, or recovery.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Nutrire
Year
2025
Authors
Geison Rivera-Bermúdez, María Fernanda Pizarro-Segura, Dayana Quesada-Quesada, M. Segura-Buján, Reza Zare, G. Gómez, Alan A. Aragon
Related Content
Claims (6)
Taking leucine supplements won’t help young athletes build more muscle, get stronger, or recover faster—even though leucine is known to trigger a muscle-growth signal in the body.
Taking leucine supplements won’t help healthy, fit young people build more muscle than taking a sugar pill, even if the supplement is strong enough to trigger a muscle-growth signal in the body.
Even though leucine (a protein building block) turns on muscle-growth signals in the body, if you're already eating enough protein, taking extra leucine won't make you stronger, bigger, or recover faster.
Taking extra leucine pills won’t help you build more muscle, get stronger, or recover faster from weight training if you’re already eating enough protein.
Taking leucine supplements won't help you recover faster from tough workouts if you're already fit and healthy — your muscles will bounce back just as well with a fake pill.
Taking leucine supplements won’t make you stronger in the gym if you’re already a healthy, trained young adult lifting weights—even if you take up to 5 grams a day for a couple of months.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.