Review: L-Carnitine supplementation could aid post-exercise muscle recovery

By Olivia Haslam

- Last updated on GMT

GettyImages - Athlete
GettyImages - Athlete

Related tags sports recovery athletes Sports nutrition supplementation L-carnitine

A new systematic review has investigated the impact of L-carnitine supplementation on muscle bioenergetics and its potential as an antioxidant in physically active individuals.

Results presented by authors from Spain suggest that L-carnitine supplementation may serve as an ergogenic aid​, aiding in muscle recovery and damage, especially in cases of L-carnitine deficiency.

Post-exercise L-carnitine supplementation

Exercise-induced muscle damage encompasses both structural and functional aspects, leading to weakened strength, fatigue, muscle pain, and cramping. 

Exercise is known to induce oxidative stress, characterised by​ an upsurge in free radical production from mitochondrial activity and an increase in muscle inflammation.

The use of nutritional supplements is widely prevalent​ in sports practice as they help prevent nutritional deficiencies, enhance performance, and promote effective recovery after exercise.

Previous studies have provided evidence supporting the potential benefits of nutritional supplements​, including L-carnitine, in the treatment of muscle damage. 

In the human body, L-carnitine (3-hydroxy-4-N​-trimethylammonium-butyrate) is produced from the amino acids lysine and methionine.

L-carnitine is essential for cellular energy metabolism and acts as an antioxidant, and it has been estimated​ that 75% of total body carnitine levels come from diet and only 25% from endogenous synthesis.

Supplementing with L-carnitine increases its levels in the blood​, promoting improved blood flow and oxygen delivery to muscles, thereby reducing hypoxic damage and aiding in recovery after exercise-induced stress. 

The review

The review focused on examining the efficacy of L-carnitine​ supplementation in the treatment of post-exercise muscular damage using 15 studies.

To conduct the review, a structured search was performed on SCOPUS, Medline (PubMed), and Web of Science (WOS) databases.

The inclusion criteria for this review encompassed randomised, double-blind controlled studies with a parallel design involving either animal samples or human subjects.

Results suggest that L-carnitine supplementation can have multiple positive effects on exercise performance and recovery. 

The supplementation was found​ to improve lipid oxidation, preserve muscle glycogen, reduce inflammation, and potentially accelerate recovery from exercise-induced muscle injury. 

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Mechanism of Action

The inflammatory response derived from muscle damage after intense exercise is largely the result of an increase in reactive oxygen species (ROS) production.

L-Carnitine, which is synthesised in the liver, kidney, and brain, needs to be transported from the bloodstream to muscle cells. 

While some studies​ have shown increased levels of L-carnitine in the bloodstream after supplementation, muscle uptake appears to be a longer process.

The beneficial effects of L-carnitine supplementation have been observed in both healthy individuals and those with certain health conditions. 

One study​ observed that L-carnitine supplementation is effective in attenuating the signs of tissue damage induced by exercise. 

Additionally, one dog-model study​ observed that the administration of L-carnitine increased muscle contractile force by 30% accompanied by an increase in blood flow.

The authors of that study hypothesised that L-carnitine exerts an effect on the vascular cells surrounding muscle and thereby increasing oxygen delivery.

The authors of the review conclude that L-carnitine supplementation shows promise in enhancing exercise recovery and performance, although further research is needed to fully understand its mechanisms and establish consistent results.

Limitations

The authors note some limitations. They state that the review consisted of studies conducted on small sample sizes, predominantly of middle-aged individuals, which raised concerns about its applicability to the broader population. 

They note that the review’s limited participant pool may restrict the generalisability of its findings, and further research involving a more diverse and representative population is necessary to draw more robust conclusions.

 

Journal: Nutrients

https://www.mdpi.com/2072-6643/15/11/2587

“Effects of L-Carnitine Intake on Exercise-Induced Muscle Damage and Oxidative Stress: A Narrative Scoping Review”

Authors: Alberto Caballero-García, David C. Noriega-González, Enrique Roche, Franchek Drobnic and Alfredo Córdova.

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