The bright and the dark sides of L-carnitine supplementation: a systematic review - PubMed (original) (raw)

The bright and the dark sides of L-carnitine supplementation: a systematic review

Angelika K Sawicka et al. J Int Soc Sports Nutr. 2020.

Abstract

Background: L-carnitine (LC) is used as a supplement by recreationally-active, competitive and highly trained athletes. This systematic review aims to evaluate the effect of prolonged LC supplementation on metabolism and metabolic modifications.

Methods: A literature search was conducted in the MEDLINE (via PubMed) and Web of Science databases from the inception up February 2020. Eligibility criteria included studies on healthy human subjects, treated for at least 12 weeks with LC administered orally, with no drugs or any other multi-ingredient supplements co-ingestion.

Results: The initial search retrieved 1024 articles, and a total of 11 studies were finally included after applying inclusion and exclusion criteria. All the selected studies were conducted with healthy human subjects, with supplemented dose ranging from 1 g to 4 g per day for either 12 or 24 weeks. LC supplementation, in combination with carbohydrates (CHO) effectively elevated total carnitine content in skeletal muscle. Twenty-four-weeks of LC supplementation did not affect muscle strength in healthy aged women, but significantly increased muscle mass, improved physical effort tolerance and cognitive function in centenarians. LC supplementation was also noted to induce an increase of fasting plasma trimethylamine-N-oxide (TMAO) levels, which was not associated with modification of determined inflammatory nor oxidative stress markers.

Conclusion: Prolonged LC supplementation in specific conditions may affect physical performance. On the other hand, LC supplementation elevates fasting plasma TMAO, compound supposed to be pro-atherogenic. Therefore, additional studies focusing on long-term supplementation and its longitudinal effect on the cardiovascular system are needed.

Keywords: Atrogin-1; Forkhead box O; Insulin-like growth factor-1; Mammalian target of rapamycin; MuRF-1; Protein kinase B; Trimethylamine-N-oxide.

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Conflict of interest statement

The authors declare that they have no competing interests.

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References

    1. Bremer J. Carnitine--metabolism and functions. Physiol Rev. 1983;63(4):1420–1480. doi: 10.1152/physrev.1983.63.4.1420. - DOI - PubMed
    1. Arenas J, Huertas R, Campos Y, Diaz AE, Villalon JM, Vilas E. Effects of L-carnitine on the pyruvate dehydrogenase complex and carnitine palmitoyl transferase activities in muscle of endurance athletes. FEBS Lett. 1994;341(1):91–93. doi: 10.1016/0014-5793(94)80246-7. - DOI - PubMed
    1. Ringseis R, Keller J, Eder K. Mechanisms underlying the anti-wasting effect of L-carnitine supplementation under pathologic conditions: evidence from experimental and clinical studies. Eur J Nutr. 2013;52(5):1421–1442. doi: 10.1007/s00394-013-0511-0. - DOI - PubMed
    1. Brass EP. Supplemental carnitine and exercise. Am J Clin Nutr. 2000;72(2 Suppl):618S–623S. doi: 10.1093/ajcn/72.2.618S. - DOI - PubMed
    1. Wall BT, Stephens FB, Constantin-Teodosiu D, Marimuthu K, Macdonald IA, Greenhaff PL. Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. J Physiol. 2011;589(Pt 4):963–973. doi: 10.1113/jphysiol.2010.201343. - DOI - PMC - PubMed

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