Carnitine supplementation - two sides of a coin

Abstract

The opinion that carnitine supplementation does not change metabolism, especially exercise metabolism, is based mainly on short-term supplementation protocols. Recent studies suggest that the period of supplementation and the stimulation of insulin-dependent transport to muscle cells may be the key factors. Carnitine supplementation, in combination with simple carbohydrates (for activation carnitine transport into the muscles), should take at least ~100 days to increase muscle carnitine content by ~10%. It can affect not only the metabolism of fatty acids and carbohydrates but also of proteins. On the other hand, long-term carnitine supplementation elevates circulating trimethylamine N-oxide (TMAO), a compound supposed to be pro-atherogenic. Therefore, further research is recommended for a better understanding of the impact of carnitine supplementation and TMAO activity mechanisms.