Leucine — Research Evidence
Source: PubMed / NCBI · human studies preferred · ranked by evidence qualityLast analyzed: May 26, 2026
🟡Moderate Evidence
20 studies·3 RCTs·13 reviews
The summary below was generated by an AI system (Claude) based on the studies listed. It is a synthesis tool, not a clinical opinion. Read individual studies for full context.
The research base on leucine as a supplement spans multiple study types, including meta-analyses, systematic reviews, and randomized controlled trials, with a particular focus on its role in muscle protein synthesis, sarcopenia treatment, and rehabilitation. Leucine is a branched-chain amino acid that appears to play a meaningful role in stimulating muscle building pathways, and it is frequently studied both in isolation and as part of combined nutritional protocols — often alongside whey protein and vitamin D. The overall body of evidence suggests leucine-containing supplementation can support muscle mass and strength outcomes, particularly in older adults and those with muscle-wasting conditions, though the magnitude of benefit and optimal protocols remain areas of active investigation.
Key findings
- ✓Meta-analyses and systematic reviews support that leucine-enriched whey protein supplementation may benefit individuals with sarcopenia, particularly older adults, by supporting muscle mass and functional outcomes.
- ✓Protein supplementation combined with resistance training shows consistent positive effects on muscle mass and strength in healthy adults, with leucine identified as a key driver of the anabolic response, according to a strong-quality meta-analysis.
- ✓Leucine and branched-chain amino acids (BCAAs) alone may have limited muscle-building effects without adequate total dietary protein intake, as highlighted in narrative reviews questioning whether isolated BCAA supplementation is sufficient for meaningful hypertrophy.
- ✓RCT evidence suggests that muscle-targeted nutritional supplements — often containing leucine — can improve rehabilitation outcomes in sarcopenic patients, though study quality is generally rated moderate.
- ✓Leucine's metabolite HMB (beta-hydroxy-beta-methylbutyrate) has been reviewed as a potentially useful adjunct for muscle preservation, particularly in clinical and aging populations, though evidence quality is moderate.
Evidence gaps
- ?Most studies lack detailed reporting on population characteristics, sample sizes, and specific dosing protocols for leucine in isolation, making it difficult to establish clear dose-response relationships or optimal supplementation strategies.
- ?The majority of the evidence base relies on reviews and meta-analyses of combined supplement protocols (e.g., whey + leucine + vitamin D), making it hard to isolate leucine's independent contribution to observed benefits.
- ?Long-term safety and efficacy data for leucine supplementation across diverse populations — including younger adults, athletic populations, and those with chronic disease — remain limited within the available studies.
Safety summary
Leucine and BCAA supplementation appear to be generally well tolerated in the populations studied, with no major safety concerns flagged across the available reviews and trials. However, the reviewed literature does not provide comprehensive long-term safety data, so caution is warranted for high-dose or extended use without medical supervision.
Studies (20)
Effects of Whey Protein, Leucine, and Vitamin D Supplementation in Patients with Sarcopenia: A Systematic Review and Meta-Analysis.
Nutrients · 2023 · Chang MC et al.
Meta-Analysis🟢
Key finding
Effects of Whey Protein, Leucine, and Vitamin D Supplementation in Patients with Sarcopenia: A Systematic Review and Meta-Analysis.
COI: The authors declare no conflict of interest.
PMID: 36771225DOI: 10.3390/nu15030521
View on PubMed A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults.
British journal of sports medicine · 2018 · Morton RW et al.
Meta-Analysis🟢
Key finding
A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults.
Funded by: Industry (inferred from affiliations)
COI: Competing interests: SMP has received grant support, travel expenses, and honoraria for presentations from the US National Dairy Council. This agency has supported trials reviewed in this analysis.
PMID: 28698222DOI: 10.1136/bjsports-2017-097608
View on PubMed Nutritional interventions for preventing and treating pressure ulcers.
The Cochrane database of systematic reviews · 2024 · Langer G et al.
Meta-Analysis🟢
Key finding
Nutritional interventions for preventing and treating pressure ulcers.
COI: G Langer: no conflict of interest
CS Wan: no conflict of interest
D Schoberer: no conflict of interest
L Schwingshackl: no conflict of interest
A Fink: no conflict of interest
PMID: 38345088DOI: 10.1002/14651858.CD003216.pub3
View on PubMed Nutritional interventions to improve muscle mass, muscle strength, and physical performance in older people: an umbrella review of systematic reviews and meta-analyses.
Nutrition reviews · 2021 · Gielen E et al.
Meta-Analysis🟢
Key finding
Nutritional interventions to improve muscle mass, muscle strength, and physical performance in older people: an umbrella review of systematic reviews and meta-analyses.
PMID: 32483625DOI: 10.1093/nutrit/nuaa011
View on PubMed Prevalence of and interventions for sarcopenia in ageing adults: a systematic review. Report of the International Sarcopenia Initiative (EWGSOP and IWGS).
Age and ageing · 2014 · Cruz-Jentoft AJ et al.
Systematic Review🟢
Key finding
Prevalence of and interventions for sarcopenia in ageing adults: a systematic review. Report of the International Sarcopenia Initiative (EWGSOP and IWGS).
Funded by: Industry (inferred from affiliations)
PMID: 25241753DOI: 10.1093/ageing/afu115
View on PubMed Nutritional Interventions to Improve Cachexia Outcomes in Cancer-A Systematic Review.
Medicina (Kaunas, Lithuania) · 2022 · Braha A et al.
Systematic Review🟢
Key finding
Nutritional Interventions to Improve Cachexia Outcomes in Cancer-A Systematic Review.
Funded by: Industry (inferred from affiliations)
COI: The authors declare no conflict of interest.
PMID: 35888685DOI: 10.3390/medicina58070966
View on PubMed Improving rehabilitation in sarcopenia: a randomized-controlled trial utilizing a muscle-targeted food for special medical purposes.
Journal of cachexia, sarcopenia and muscle · 2020 · Rondanelli M et al.
RCT🟡
Key finding
Improving rehabilitation in sarcopenia: a randomized-controlled trial utilizing a muscle-targeted food for special medical purposes.
COI: All authors have completed the Unified Competing Interest form (available on request from the corresponding author) and declare: no support from any organisation for the submitted work. Dr Cereda reports the following conflicts of interest (not for the present study): Consulting or Advisory Role: Nutricia S. p. A., Akern S.r.l., Wunder Sa.Bi. s.r.l., Fondazione Grigioni per il Morbo di Parkinson. Speaker's Honoraria: Nutricia S. p. A., Nestlè Health Science.
Dr Klersy is a statistical consultant with Nutricia S. p. A. (inclusive of the present work). All the other authors declare no financial relationships with any organisations that might have an interest in the submitted work in the previous three years. All authors declare no other relationships or activities that could appear to have influenced the submitted work.
PMID: 32961041DOI: 10.1002/jcsm.12532
View on PubMed Supplement-based nutritional strategies to tackle frailty: A multifactorial, double-blind, randomized placebo-controlled trial.
Clinical nutrition (Edinburgh, Scotland) · 2021 · Roschel H et al.
RCT🟡
Key finding
Supplement-based nutritional strategies to tackle frailty: A multifactorial, double-blind, randomized placebo-controlled trial.
COI: Conflict of interest SMP reports personal fees from Enhanced Recovery, equity from Exerkine, personal fees from Dairy Farmers of Canada, personal fees from US National Dairy Export Council, grants from Alliance for Potato Research and Education, grants from US National Dairy Council, outside the submitted work; In addition, SMP has a patent 3052324 issued to Exerkine, and a patent 16/182891 pending to Exerkine.
PMID: 34358827DOI: 10.1016/j.clnu.2021.06.024
View on PubMed Effects of a vitamin D and leucine-enriched whey protein nutritional supplement on measures of sarcopenia in older adults, the PROVIDE study: a randomized, double-blind, placebo-controlled trial.
Journal of the American Medical Directors Association · 2015 · Bauer JM et al.
RCT🟡
Key finding
Effects of a vitamin D and leucine-enriched whey protein nutritional supplement on measures of sarcopenia in older adults, the PROVIDE study: a randomized, double-blind, placebo-controlled trial.
Funded by: Medical Research Council
PMID: 26170041DOI: 10.1016/j.jamda.2015.05.021
View on PubMed Whey Protein, Leucine- and Vitamin-D-Enriched Oral Nutritional Supplementation for the Treatment of Sarcopenia.
Nutrients · 2022 · Cereda E et al.
Review🟡
Key finding
Whey Protein, Leucine- and Vitamin-D-Enriched Oral Nutritional Supplementation for the Treatment of Sarcopenia.
COI: Emanuele Cereda declares that he has no conflict of interest. Roberto Pisati has been the Medical Director of Nutricia Italia S.p.a. up to 30 June 2018. Mariangela Rondanelli declares that he has no conflict of interest. Riccardo Caccialanza declares that he has no conflict of interest.
PMID: 35406137DOI: 10.3390/nu14071524
View on PubMed Amino acids: metabolism, functions, and nutrition.
Amino acids · 2009 · Wu G
Review🟡
Key finding
Amino acids: metabolism, functions, and nutrition.
Funded by: NICHD NIH HHS
PMID: 19301095DOI: 10.1007/s00726-009-0269-0
View on PubMed Branched-chain amino acids and muscle protein synthesis in humans: myth or reality?
Journal of the International Society of Sports Nutrition · 2017 · Wolfe RR
Review🟡
Key finding
Branched-chain amino acids and muscle protein synthesis in humans: myth or reality?
COI: ETHICS APPROVAL AND CONSENT TO PARTICIPATE: Not Applicable. CONSENT FOR PUBLICATION: Not Applicable. COMPETING INTERESTS: Dr. Wolfe has received research grants and/or honoraria from the National Cattleman’s Beef Checkoff program Abbott Nutrition, Danone and PepsiCo. Dr. Wolfe owns shares in Essential Blends, LLC, and has been a consultant for Axcella LLC. PUBLISHER’S NOTE: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
PMID: 28852372DOI: 10.1186/s12970-017-0184-9
View on PubMed Advances in muscle health and nutrition: A toolkit for healthcare professionals.
Clinical nutrition (Edinburgh, Scotland) · 2022 · Prado CM et al.
Review🟡
Key finding
Advances in muscle health and nutrition: A toolkit for healthcare professionals.
COI: Conflict of interest C.M.P. has previously received honoraria and/or paid consultancy from Abbott Nutrition, Nutricia, Nestlé Health Science, Fresenius Kabi, and Pfizer. T.R. reports grants from German Ministry of Education, Science, Research and Technology; grants and personal fees from Sanofi-Aventis and Alexion; personal fees from Abbott Nutrition, Argenx, Biogen, BMS, Roche, Novartis, and Teva; and personal fees and nonfinancial support from Merck Serono, outside the submitted work. S.T.H.C has previously received grant co-funding, travel grant and honoraria from Abbott Nutrition. M.C.G. has received paid consultancy from Abbott Nutrition and Nestlé Brazil. F.L., P.J.A, J.M., T.B. have previously received grant funding and paid consultancy from Abbott Nutrition.
PMID: 36081299DOI: 10.1016/j.clnu.2022.07.041
View on PubMed International society of sports nutrition position stand: β-hydroxy-β-methylbutyrate (HMB).
Journal of the International Society of Sports Nutrition · 2025 · Rathmacher JA et al.
Review🟡
Key finding
International society of sports nutrition position stand: β-hydroxy-β-methylbutyrate (HMB).
Funded by: Industry (inferred from affiliations)
COI: JAR is currently employed by MTI Biotech Inc., Ames IA and continues his research with HMB studies. JAR was a principal investigator for clinical and animal studies with HMB while previously employed at Metabolic Technologies, Inc., which until recently had marketed HMB-Ca and HMB-FA. JAR is listed as an inventor on a number of active HMB-related patents. JAR has received federal grants to conduct research on HMB-Ca. LMP is a former full-time employee of and current consultant for MTI Biotech Inc., Ames IA. LMP was involved in the conduct and reporting of results for clinical and animal studies with HMB while previously employed at Metabolic Technologies, Inc., which until recently had marketed HMB-Ca and HMB-FA. LMP is listed as an inventor on active HMB-related patents. JRT has no conflict of interest related to this manuscript in terms of financial or business interests. JRT has received grants and contracts to conduct research on dietary supplements, has served as a paid consultant for industry, and has received honoraria for speaking at conferences. JRT is listed as an inventor of previously filed HMB-related patents. JRS has no conflict of interest related to this manuscript in terms of financial or business interests. He has received grants and contracts to conduct research on dietary supplements, including HMB, over the past 25 years. He has also served as a paid consultant for the industry and received honoraria for speaking at conferences and writing lay articles about sports nutrition ingredients and topics. In addition, JRS has received financial support from the National Institute on Aging (R03AG06799) and the National Institute on Minority Health and Health Disparities (R01MD018025). RJ has received grants and contracts to conduct research on dietary supplements; has served as a paid consultant for industry; has received honoraria for speaking at conferences and has served as an expert witness on behalf of the plaintiff and defense in cases involving dietary supplements. RJ is listed as an inventor of HMB-related patents. CMK has received grants and contracts to conduct research on dietary supplements; has served as a paid consultant for industry and has received honoraria for speaking at conferences involving dietary supplements. CMK currently serves as the President of the International Society of Sports Nutrition (ISSN). PSH has received grants and in-kind support to conduct research on dietary supplements and has received honoraria for speaking at conferences involving dietary supplements. DGC has conducted industry-sponsored research involving creatine supplementation and received creatine donations for scientific studies and travel support for presentations involving creatine supplementation at scientific conferences. In addition, DGC. serves on the Scientific Advisory Board for Alzchem and Create (companies that manufacture creatine products) and as an expert witness/consultant in legal cases involving creatine supplementation. BMR has no poteintial conflicts of interest related to this manuscript. SMA has received federal and industry grants to conduct research on dietary supplements, has served as a paid consultant for industry, and has received honoraria for speaking at conferences involving dietary supplements. DSK has received research grants and honorarium from companies in the dietary supplement and foods industry. This includes companies that may retail HMB. JA is the CEO of the International Society of Sports Nutrition (ISSN), which is a 501c3 academic non-profit. The ISSN has received on occasion grant support from companies that sell, market, or manufacture HMB. The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or reflecting the views of the Army or the Department of Defense. Any citations of commercial organizations and trade names in this report do not constitute an official Department of the Army endorsement of approval of the products or services of these organizations
PMID: 39699070DOI: 10.1080/15502783.2024.2434734
View on PubMed Emerging Targets and Treatments for Sarcopenia: A Narrative Review.
Nutrients · 2024 · Cacciatore S et al.
Review🟡
Key finding
Emerging Targets and Treatments for Sarcopenia: A Narrative Review.
Funded by: Università Cattolica del Sacro Cuore, Ministero dell'Istruzione e del Merito, European Commission, Centro Studi Achille e Linda Lorenzon
COI: The funders had no role in the writing of the manuscript or in the decision to publish it. The authors declare no conflicts of interest.
PMID: 39408239DOI: 10.3390/nu16193271
View on PubMed Beta-hydroxy-beta-methylbutyrate supplementation and skeletal muscle in healthy and muscle-wasting conditions.
Journal of cachexia, sarcopenia and muscle · 2017 · Holeček M
Review🟡
Key finding
Beta-hydroxy-beta-methylbutyrate supplementation and skeletal muscle in healthy and muscle-wasting conditions.
PMID: 28493406DOI: 10.1002/jcsm.12208
View on PubMed Rehabilitation Nutrition for Injury Recovery of Athletes: The Role of Macronutrient Intake.
Nutrients · 2020 · Papadopoulou SK
Review🟡
Key finding
Rehabilitation Nutrition for Injury Recovery of Athletes: The Role of Macronutrient Intake.
COI: The author declares no conflict of interest.
PMID: 32824034DOI: 10.3390/nu12082449
View on PubMed Isolated Leucine and Branched-Chain Amino Acid Supplementation for Enhancing Muscular Strength and Hypertrophy: A Narrative Review.
International journal of sport nutrition and exercise metabolism · 2021 · Plotkin DL et al.
Review🟡
Key finding
Isolated Leucine and Branched-Chain Amino Acid Supplementation for Enhancing Muscular Strength and Hypertrophy: A Narrative Review.
PMID: 33741748DOI: 10.1123/ijsnem.2020-0356
View on PubMed Dietary protein recommendations and the prevention of sarcopenia.
Current opinion in clinical nutrition and metabolic care · 2009 · Paddon-Jones D et al.
Review🟡
Key finding
Dietary protein recommendations and the prevention of sarcopenia.
Funded by: NIA NIH HHS, NIAMS NIH HHS
PMID: 19057193DOI: 10.1097/MCO.0b013e32831cef8b
View on PubMed Acute Sarcopenia: Mechanisms and Management.
Nutrients · 2024 · Damanti S et al.
Review🟡
Key finding
Acute Sarcopenia: Mechanisms and Management.
Funded by: European Union - Next Generation EU - NRRP M6C2 - Investment 2.1 Enhancement and strengthening of biomedical research in the NHS
COI: The authors declare no conflicts of interest.
PMID: 39458423DOI: 10.3390/nu16203428
View on PubMed