Shared Mechanisms and Differential Effects of L-Carnitine Supplementation in Athletes and Cardiometabolically Impaired Individuals
DOI:
https://doi.org/10.12775/QS.2025.48.67108Keywords
L-carnitine, fatty acid oxidation, mitochondrial function, exercise performance, cardiometabolic health, heart failure, muscle recovery, oxidative stress, supplementation, TMAOAbstract
Introduction and purpose:
L-carnitine is a key component of mitochondrial fatty acid transport and energy metabolism. Owing to its metabolic importance, it is widely studied in the context of exercise performance and cardiometabolic disorders. This review aims to assess current evidence on its metabolic actions, effectiveness in physical performance and recovery, and its therapeutic potential in cardiovascular and metabolic diseases.
Material and methods:
A literature search was performed in PubMed, Google Scholar and ResearchGate using the keywords. Studies were analyzed for mechanisms of action, supplementation effects, clinical outcomes and safety.
Results:
L-carnitine enhances mitochondrial β-oxidation, regulates the acyl-CoA/CoA ratio and reduces oxidative stress. In athletes, chronic supplementation may increase fat oxidation during moderate-intensity exercise and reduce markers of muscle damage, but it does not significantly improve VO₂max or endurance. In individuals with metabolic disorders, L-carnitine improves insulin sensitivity, lipid profile, metabolic flexibility and cardiac function. Supplementation increases TMAO levels, although its clinical importance remains uncertain.
Conclusions:
L-carnitine shows benefits for exercise recovery and significant improvements in metabolic and cardiovascular dysfunction. Its effects vary depending on baseline metabolic status and carnitine levels. Future research should focus on standardized dosing strategies, long-term effects, and clarifying the clinical relevance of TMAO elevation.
References
Almannai, M., Alfadhel, M., & El-Hattab, A. W. (2019). Carnitine Inborn Errors of Metabolism. Molecules, 24(18), 3251. https://doi.org/10.3390/molecules24183251
Gnoni, A., Longo, S., Gnoni, G. V., & Giudetti, A. M. (2020). Carnitine in Human Muscle Bioenergetics: Can Carnitine Supplementation Improve Physical Exercise? Molecules, 25(1), 182. https://doi.org/10.3390/molecules25010182
Calvani, M., Reda, E., & Arrigoni-Martelli, E. (2000). Regulation by carnitine of myocardial fatty acid and carbohydrate metabolism under normal and pathological conditions. Basic Research in Cardiology, 95(2), 75–83. https://doi.org/10.1007/s003950050167
Almannai, M., Alfadhel, M., & El-Hattab, A. W. (2019). Carnitine Inborn Errors of Metabolism. Molecules, 24(18), 3251. https://doi.org/10.3390/molecules24183251
Longo, N., Frigeni, M., & Pasquali, M. (2016). Carnitine transport and fatty acid oxidation. Biochimica et Biophysica Acta (BBA) - Molecular Cell Research, 1863(10), 2422–2435. https://doi.org/10.1016/j.bbamcr.2016.01.023
Virmani, M. A., & Cirulli, M. (2022). The Role of l-Carnitine in Mitochondria, Prevention of Metabolic Inflexibility and Disease Initiation. International Journal of Molecular Sciences, 23(5), 2717. https://doi.org/10.3390/ijms23052717
Stephens, F. B. (2017). Does skeletal muscle carnitine availability influence fuel selection during exercise? Proceedings of the Nutrition Society, 77(1), 11–19. https://doi.org/10.1017/s0029665117003937
Wall, B. T., Stephens, F. B., Constantin‐Teodosiu, D., Marimuthu, K., Macdonald, I. A., & Greenhaff, P. L. (2011). Chronic oral ingestion of l ‐carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. The Journal of Physiology, 589(4), 963–973. https://doi.org/10.1113/jphysiol.2010.201343
Stephens, F. B., Constantin‐Teodosiu, D., & Greenhaff, P. L. (2007). New insights concerning the role of carnitine in the regulation of fuel metabolism in skeletal muscle. The Journal of Physiology, 581(2), 431–444. https://doi.org/10.1113/jphysiol.2006.125799
Gnoni, A., Longo, S., Gnoni, G. V., & Giudetti, A. M. (2020). Carnitine in Human Muscle Bioenergetics: Can Carnitine Supplementation Improve Physical Exercise? Molecules, 25(1), 182. https://doi.org/10.3390/molecules25010182
Mielgo-Ayuso, J., Pietrantonio, L., Viribay, A., Calleja-González, J., González-Bernal, J., & Fernández-Lázaro, D. (2021). Effect of Acute and Chronic Oral l-Carnitine Supplementation on Exercise Performance Based on the Exercise Intensity: A Systematic Review. Nutrients, 13(12), 4359. https://doi.org/10.3390/nu13124359
Sawicka, A. K., Renzi, G., & Olek, R. A. (2020). The bright and the dark sides of L-carnitine supplementation: a systematic review. Journal of the International Society of Sports Nutrition, 17(1). https://doi.org/10.1186/s12970-020-00377-2
Yarizadh, H., Shab-Bidar, S., Zamani, B., Vanani, A. N., Baharlooi, H., & Djafarian, K. (2020). The Effect of L-Carnitine Supplementation on Exercise-Induced Muscle Damage: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. Journal of the American College of Nutrition, 39(5), 457–468. https://doi.org/10.1080/07315724.2019.1661804
Ho, J.-Y., Kraemer, W. J., Volek, J. S., Fragala, M. S., Thomas, G. A., Dunn-Lewis, C., Coday, M., Häkkinen, K., & Maresh, C. M. (2010). l-Carnitine l-tartrate supplementation favorably affects biochemical markers of recovery from physical exertion in middle-aged men and women. Metabolism, 59(8), 1190–1199. https://doi.org/10.1016/j.metabol.2009.11.012
Stefan, M., Sharp, M., Gheith, R., Lowery, R., Ottinger, C., Wilson, J., Durkee, S., & Bellamine, A. (2021). L-Carnitine Tartrate Supplementation for 5 Weeks Improves Exercise Recovery in Men and Women: A Randomized, Double-Blind, Placebo-Controlled Trial. Nutrients, 13(10), 3432. https://doi.org/10.3390/nu13103432
Volek, J. S., Kraemer, W. J., Rubin, M. R., Gómez, A. L., Ratamess, N. A., & Gaynor, P. (2002). L-Carnitine l-tartrate supplementation favorably affects markers of recovery from exercise stress. American Journal of Physiology-Endocrinology and Metabolism, 282(2), E474–E482. https://doi.org/10.1152/ajpendo.00277.2001
Mielgo-Ayuso, J., Pietrantonio, L., Viribay, A., Calleja-González, J., González-Bernal, J., & Fernández-Lázaro, D. (2021). Effect of Acute and Chronic Oral l-Carnitine Supplementation on Exercise Performance Based on the Exercise Intensity: A Systematic Review. Nutrients, 13(12), 4359. https://doi.org/10.3390/nu13124359
Gnoni, A., Longo, S., Gnoni, G. V., & Giudetti, A. M. (2020). Carnitine in Human Muscle Bioenergetics: Can Carnitine Supplementation Improve Physical Exercise? Molecules, 25(1), 182. https://doi.org/10.3390/molecules25010182
Fielding, R., Riede, L., Lugo, J., & Bellamine, A. (2018). l-Carnitine Supplementation in Recovery after Exercise. Nutrients, 10(3), 349. https://doi.org/10.3390/nu10030349
Stefan, M., Sharp, M., Gheith, R., Lowery, R., Ottinger, C., Wilson, J., Durkee, S., & Bellamine, A. (2021). L-Carnitine Tartrate Supplementation for 5 Weeks Improves Exercise Recovery in Men and Women: A Randomized, Double-Blind, Placebo-Controlled Trial. Nutrients, 13(10), 3432. https://doi.org/10.3390/nu13103432
Yarizadh, H., Shab-Bidar, S., Zamani, B., Vanani, A. N., Baharlooi, H., & Djafarian, K. (2020). The Effect of L-Carnitine Supplementation on Exercise-Induced Muscle Damage: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. Journal of the American College of Nutrition, 39(5), 457–468. https://doi.org/10.1080/07315724.2019.1661804
Brass, E. P., & Hiatt, W. R. (1998). The Role of Carnitine and Carnitine Supplementation During Exercise in Man and in Individuals with Special Needs. Journal of the American College of Nutrition, 17(3), 207–215. https://doi.org/10.1080/07315724.1998.10718750
Alhasaniah, A. H. (2023). l-carnitine: Nutrition, pathology, and health benefits. Saudi Journal of Biological Sciences, 30(2), 103555. https://doi.org/10.1016/j.sjbs.2022.103555
BRASS, E. P. (2004). Carnitine and Sports Medicine: Use or Abuse? Annals of the New York Academy of Sciences, 1033(1), 67–78. https://doi.org/10.1196/annals.1320.006
Sawicka, A. K., Renzi, G., & Olek, R. A. (2020). The bright and the dark sides of L-carnitine supplementation: a systematic review. Journal of the International Society of Sports Nutrition, 17(1). https://doi.org/10.1186/s12970-020-00377-2
Gnoni, A., Longo, S., Gnoni, G. V., & Giudetti, A. M. (2020). Carnitine in Human Muscle Bioenergetics: Can Carnitine Supplementation Improve Physical Exercise? Molecules, 25(1), 182. https://doi.org/10.3390/molecules25010182
Li, Y., Xie, Y., Qiu, C., Yu, B., Yang, F., Cheng, Y., Zhong, W., & Yuan, J. (2023). Effects of l-carnitine supplementation on glucolipid metabolism: a systematic review and meta-analysis. Food & Function, 14(5), 2502–2517. https://doi.org/10.1039/d2fo02930h
Choi, M., Park, S., & Lee, M. (2020). L-Carnitine’s Effect on the Biomarkers of Metabolic Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Nutrients, 12(9), 2795. https://doi.org/10.3390/nu12092795
Op den Kamp‐Bruls, Y. M. H., Op den Kamp, Y. J. M., Veeraiah, P., Zapata Perez, R., Phielix, E., Havekes, B., Schaart, G., Kornips, E., Berendsen, B. R. B., Virmani, A., Wildberger, J. E., Houtkooper, R. H., Hesselink, M. K. C., Schrauwen, P., & Schrauwen‐Hinderling, V. B. (2025). Carnitine supplementation improves insulin sensitivity and skeletal muscle acetylcarnitine formation in patients with type 2 diabetes. Diabetes, Obesity and Metabolism, 27(5), 2864–2877. https://doi.org/10.1111/dom.16298
Asadi, M., Rahimlou, M., Shishehbor, F., & Mansoori, A. (2020). The effect of l-carnitine supplementation on lipid profile and glycaemic control in adults with cardiovascular risk factors: A systematic review and meta-analysis of randomized controlled clinical trials. Clinical Nutrition, 39(1), 110–122. https://doi.org/10.1016/j.clnu.2019.01.020
Oyanagi, E., Yano, H., Uchida, M., Utsumi, K., & Sasaki, J. (2011). Protective action of l-carnitine on cardiac mitochondrial function and structure against fatty acid stress. Biochemical and Biophysical Research Communications, 412(1), 61–67. https://doi.org/10.1016/j.bbrc.2011.07.039
Vacante, F., Senesi, P., Montesano, A., Frigerio, A., Luzi, L., & Terruzzi, I. (2018). L-Carnitine: An Antioxidant Remedy for the Survival of Cardiomyocytes under Hyperglycemic Condition. Journal of Diabetes Research, 2018, 1–12. https://doi.org/10.1155/2018/4028297
Vacante, F., Senesi, P., Montesano, A., Frigerio, A., Luzi, L., & Terruzzi, I. (2018). L-Carnitine: An Antioxidant Remedy for the Survival of Cardiomyocytes under Hyperglycemic Condition. Journal of Diabetes Research, 2018, 1–12. https://doi.org/10.1155/2018/4028297
FERRARI, R., MERLI, E., CICCHITELLI, G., MELE, D., FUCILI, A., & CECONI, C. (2004). Therapeutic Effects of l‐Carnitine and Propionyl‐l‐carnitine on Cardiovascular Diseases: A Review. Annals of the New York Academy of Sciences, 1033(1), 79–91. https://doi.org/10.1196/annals.1320.007
Song, X., Qu, H., Yang, Z., Rong, J., Cai, W., & Zhou, H. (2017). Efficacy and Safety of L-Carnitine Treatment for Chronic Heart Failure: A Meta-Analysis of Randomized Controlled Trials. BioMed Research International, 2017, 1–11. https://doi.org/10.1155/2017/6274854
DiNicolantonio, J. J., Lavie, C. J., Fares, H., Menezes, A. R., & O’Keefe, J. H. (2013). L-Carnitine in the Secondary Prevention of Cardiovascular Disease: Systematic Review and Meta-analysis. Mayo Clinic Proceedings, 88(6), 544–551. https://doi.org/10.1016/j.mayocp.2013.02.007
Colonna, P., & Iliceto, S. (2000). Myocardial infarction and left ventricular remodeling: Results of the CEDIM trial. American Heart Journal, 139(2), s124–s130. https://doi.org/10.1067/mhj.2000.103918
Song, X., Qu, H., Yang, Z., Rong, J., Cai, W., & Zhou, H. (2017). Efficacy and Safety of L-Carnitine Treatment for Chronic Heart Failure: A Meta-Analysis of Randomized Controlled Trials. BioMed Research International, 2017, 1–11. https://doi.org/10.1155/2017/6274854
DiNicolantonio, J. J., Lavie, C. J., Fares, H., Menezes, A. R., & O’Keefe, J. H. (2013). L-Carnitine in the Secondary Prevention of Cardiovascular Disease: Systematic Review and Meta-analysis. Mayo Clinic Proceedings, 88(6), 544–551. https://doi.org/10.1016/j.mayocp.2013.02.007
Ussher, J. R., Lopaschuk, G. D., & Arduini, A. (2013). Gut microbiota metabolism of l-carnitine and cardiovascular risk. Atherosclerosis, 231(2), 456–461. https://doi.org/10.1016/j.atherosclerosis.2013.10.013
Ufnal, M., Zadlo, A., & Ostaszewski, R. (2015). TMAO: A small molecule of great expectations. Nutrition, 31(11–12), 1317–1323. https://doi.org/10.1016/j.nut.2015.05.006
Budoff, M. J., de Oliveira Otto, M. C., Li, X. S., Lee, Y., Wang, M., Lai, H. T. M., Lemaitre, R. N., Pratt, A., Tang, W. H. W., Psaty, B. M., Siscovick, D. S., Hazen, S. L., & Mozaffarian, D. (2025). Trimethylamine-N-oxide (TMAO) and risk of incident cardiovascular events in the multi ethnic study of Atherosclerosis. Scientific Reports, 15(1). https://doi.org/10.1038/s41598-025-05903-3
Thomas, M. S., & Fernandez, M. L. (2021). Trimethylamine N-Oxide (TMAO), Diet and Cardiovascular Disease. Current Atherosclerosis Reports, 23(4). https://doi.org/10.1007/s11883-021-00910-x
Fu, B. C., Hullar, M. A., Randolph, T. W., Franke, A. A., Monroe, K. R., Cheng, I., Wilkens, L. R., Shepherd, J. A., Madeleine, M. M., Le Marchand, L., Lim, U., & Lampe, J. W. (2020). Associations of plasma trimethylamine N-oxide, choline, carnitine, and betaine with inflammatory and cardiometabolic risk biomarkers and the fecal microbiome in the Multiethnic Cohort Adiposity Phenotype Study. The American Journal of Clinical Nutrition, 111(6), 1226–1234. https://doi.org/10.1093/ajcn/nqaa015
Naghipour, S., Cox, A. J., Peart, J. N., Du Toit, E. F., & Headrick, J. P. (2020). TrimethylamineN-oxide: heart of the microbiota–CVD nexus? Nutrition Research Reviews, 34(1), 125–146. https://doi.org/10.1017/s0954422420000177
Olek, R. A., Samulak, J. J., Sawicka, A. K., Hartmane, D., Grinberga, S., Pugovics, O., & Lysiak-Szydlowska, W. (2019). Increased Trimethylamine N-Oxide Is Not Associated with Oxidative Stress Markers in Healthy Aged Women. Oxidative Medicine and Cellular Longevity, 2019, 1–6. https://doi.org/10.1155/2019/6247169
Samulak, J. J., Sawicka, A. K., Samborowska, E., & Olek, R. A. (2019). Plasma Trimethylamine-N-oxide following Cessation of L-carnitine Supplementation in Healthy Aged Women. Nutrients, 11(6), 1322. https://doi.org/10.3390/nu11061322
Hathcock, J. N., & Shao, A. (2006). Risk assessment for carnitine. Regulatory Toxicology and Pharmacology, 46(1), 23–28. https://doi.org/10.1016/j.yrtph.2006.06.007
Davani-Davari, D., Karimzadeh, I., Sagheb, M. M., & Khalili, H. (2019). The Renal Safety of L-Carnitine, L-Arginine, and Glutamine in Athletes and Bodybuilders. Journal of Renal Nutrition, 29(3), 221–234. https://doi.org/10.1053/j.jrn.2018.08.014
Askarpour, M., Djafarian, K., Ghaedi, E., Sadeghi, O., Sheikhi, A., & Shab-Bidar, S. (2020). Effect of L-Carnitine Supplementation on Liver Enzymes: A Systematic Review and Meta-analysis of Randomized Controlled Trials. Archives of Medical Research, 51(1), 82–94. https://doi.org/10.1016/j.arcmed.2019.12.005
Alhasaniah, A. H. (2023). l-carnitine: Nutrition, pathology, and health benefits. Saudi Journal of Biological Sciences, 30(2), 103555. https://doi.org/10.1016/j.sjbs.2022.103555
Marcovina, S. M., Sirtori, C., Peracino, A., Gheorghiade, M., Borum, P., Remuzzi, G., & Ardehali, H. (2013). Translating the basic knowledge of mitochondrial functions to metabolic therapy: role of L-carnitine. Translational Research, 161(2), 73–84. https://doi.org/10.1016/j.trsl.2012.10.006
Virmani, M. A., & Cirulli, M. (2022). The Role of l-Carnitine in Mitochondria, Prevention of Metabolic Inflexibility and Disease Initiation. International Journal of Molecular Sciences, 23(5), 2717. https://doi.org/10.3390/ijms23052717
Caballero-García, A., Noriega-González, D. C., Roche, E., Drobnic, F., & Córdova, A. (2023). Effects of L-Carnitine Intake on Exercise-Induced Muscle Damage and Oxidative Stress: A Narrative Scoping Review. Nutrients, 15(11), 2587. https://doi.org/10.3390/nu15112587
Mielgo-Ayuso, J., Pietrantonio, L., Viribay, A., Calleja-González, J., González-Bernal, J., & Fernández-Lázaro, D. (2021). Effect of Acute and Chronic Oral l-Carnitine Supplementation on Exercise Performance Based on the Exercise Intensity: A Systematic Review. Nutrients, 13(12), 4359. https://doi.org/10.3390/nu13124359
Li, Y., Xie, Y., Qiu, C., Yu, B., Yang, F., Cheng, Y., Zhong, W., & Yuan, J. (2023). Effects of l-carnitine supplementation on glucolipid metabolism: a systematic review and meta-analysis. Food & Function, 14(5), 2502–2517. https://doi.org/10.1039/d2fo02930h
Asadi, M., Rahimlou, M., Shishehbor, F., & Mansoori, A. (2020). The effect of l-carnitine supplementation on lipid profile and glycaemic control in adults with cardiovascular risk factors: A systematic review and meta-analysis of randomized controlled clinical trials. Clinical Nutrition, 39(1), 110–122. https://doi.org/10.1016/j.clnu.2019.01.020
Wang, Z.-Y., Liu, Y.-Y., Liu, G.-H., Lu, H.-B., & Mao, C.-Y. (2018). l -Carnitine and heart disease. Life Sciences, 194, 88–97. https://doi.org/10.1016/j.lfs.2017.12.015
Virmani, M. A., & Cirulli, M. (2022). The Role of l-Carnitine in Mitochondria, Prevention of Metabolic Inflexibility and Disease Initiation. International Journal of Molecular Sciences, 23(5), 2717. https://doi.org/10.3390/ijms23052717
Alhasaniah, A. H. (2023). l-carnitine: Nutrition, pathology, and health benefits. Saudi Journal of Biological Sciences, 30(2), 103555. https://doi.org/10.1016/j.sjbs.2022.103555
Marcovina, S. M., Sirtori, C., Peracino, A., Gheorghiade, M., Borum, P., Remuzzi, G., & Ardehali, H. (2013). Translating the basic knowledge of mitochondrial functions to metabolic therapy: role of L-carnitine. Translational Research, 161(2), 73–84. https://doi.org/10.1016/j.trsl.2012.10.006
Choi, M., Park, S., & Lee, M. (2020). L-Carnitine’s Effect on the Biomarkers of Metabolic Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Nutrients, 12(9), 2795. https://doi.org/10.3390/nu12092795
Li, Y., Xie, Y., Qiu, C., Yu, B., Yang, F., Cheng, Y., Zhong, W., & Yuan, J. (2023). Effects of l-carnitine supplementation on glucolipid metabolism: a systematic review and meta-analysis. Food & Function, 14(5), 2502–2517. https://doi.org/10.1039/d2fo02930h
Gnoni, A., Longo, S., Gnoni, G. V., & Giudetti, A. M. (2020). Carnitine in Human Muscle Bioenergetics: Can Carnitine Supplementation Improve Physical Exercise? Molecules, 25(1), 182. https://doi.org/10.3390/molecules25010182
Fielding, R., Riede, L., Lugo, J., & Bellamine, A. (2018). l-Carnitine Supplementation in Recovery after Exercise. Nutrients, 10(3), 349. https://doi.org/10.3390/nu10030349
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