Acute and Chronic L-Carnitine Supplementation Enhances Endurance Performance Without Consistent Effects on Substrate Oxidation in Active Individuals: A Systematic Review.
Eryiğit H, Güzel Y, Bulut S, Turnagöl HH, Atakan MM. · International journal of sport nutrition and exercise metabolism · 2026
Objectives: This study
Aims: to systematically evaluate the effects of acute and chronic L-carnitine supplementation on endurance performance and substrate oxidation during exercise among active individuals.
Methods: This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines. A total of 647 studies were initially retrieved from PubMed/MEDLINE, Web of Science, Cochrane Library, Scopus, Ovid MEDLINE, EBSCO Open Dissertations, EBSCO Academic Search Ultimate, and SPORTDiscus databases, with searches conducted from database inception to February 1, 2026. Randomized placebo-controlled crossover and parallel-group trials were eligible for inclusion. Studies meeting the inclusion criteria were assessed using the Cochrane Risk of Bias 2 (RoB 2) tool, with the crossover-specific version applied to randomized crossover trials.
Results: A total of 18 studies met the inclusion criteria. Overall, 15 (83%) studies were rated as having some concerns, three (17%) were classified as having a high risk of bias, and none were judged to be at low risk of bias. Ten studies investigated acute L-carnitine supplementation (2-15 g), seven studies examined chronic supplementation (2-3 g/day for 2-24 weeks), and one study evaluated both acute and chronic supplementation (3 g on a single day and over 2 weeks). Both acute and chronic L-carnitine supplementation were associated with improvements in endurance performance following acute supplementation and chronic supplementation. By contrast, no significant changes in fat oxidation during exercise were reported after either acute (2-4 g ingested 120-180 min before exercise) or chronic supplementation (2 g/day for 2-4 weeks).
Conclusions: L-carnitine may enhance selected endurance performance outcomes among active individuals; however, its reputation as a "fat-burning" ergogenic aid is not supported by current evidence, following short-term supplementation.