The Study
Enriching a protein drink with leucine augments muscle protein synthesis after resistance exercise in young and older men.
This study found that when men drank a protein shake with extra leucine after lifting weights, their muscles started repairing faster than when they drank a shake without it. But it only tested 9 men in each group in a lab — so we can't say it works the same for everyone, like women or older people who don't exercise.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
Scientists gave men a protein drink after lifting weights — some got extra leucine, others got a fake ingredient. They measured how fast muscles repaired themselves.
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 546 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — even older men’s muscles responded as well as young men’s when given extra leucine, suggesting it can help overcome age-related muscle slowdown.
- 2With leucine, muscle protein synthesis increased by about 38% (0.11% vs 0.08% per hour) over 4 hours.
- 3Leucine also turned on a key muscle growth signal (p70S6K1) more in older men.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Clinical nutrition
Year
2017
Authors
P. Atherton, Vinod Kumar, A. Selby, D. Rankin, W. Hildebrandt, B. Phillips, John P. Williams, N. Hiscock, Kenneth Smith
Related Content
Claims (4)
After resistance training, the rate of muscle protein synthesis is highest between 30 and 45 minutes.
When healthy young and older men consume a drink with 10 grams of protein, 24 grams of carbohydrates, and 4.2 grams of leucine after resistance exercise, their muscle protein synthesis rates increase significantly over the next four hours compared to the same drink without leucine.
In older men, taking leucine after weight training leads to higher levels of p70S6K1 phosphorylation than taking a control substance with the same nitrogen content, which reflects greater activation of the mTOR signaling pathway.
Taking leucine after exercise increases muscle protein synthesis in older men as much as it does in younger men, even though older men typically have reduced muscle building responses to stimuli.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.