Why you should use L-Carnitine if you want to build muscle

L-carnitine (LC) can be used by recreational athletes as well as professionals. This systematic review of this substance aims to evaluate the effect of prolonged use of LC on metabolism and metabolic modifications.

A literature search was conducted in MEDLINE (via PubMed) and Web of Science databases from inception to February 2020. Eligibility criteria included studies in healthy humans treated for at least 12 weeks with LC tablets.

Results

The initial search found 1024 articles, and a total of 11 studies. All selected studies were conducted in healthy humans, with supplemental doses ranging from 1 g to 4 g per day for 12 or 24 weeks. LC supplementation, in combination with carbohydrates (CHO) effectively increased total carnitine content in skeletal muscle. Twenty-four weeks of LC supplementation did not affect muscle strength in healthy women, but significantly increased muscle mass, improved exercise tolerance, and cognitive function. LC supplementation was also observed to cause an increase in plasma levels of trimethylamine-N-oxide (TMAO), which was not associated with modification of established markers of inflammatory or oxidative stress.

Conclusion

Prolonged LC supplementation under specific conditions may affect physical performance. On the other hand, LC supplementation raises plasma TMAO, a compound that is hypothesized to be proatherogenic. Therefore, additional studies focusing on long-term supplementation and its longitudinal effect on the cardiovascular system are needed.