L-carnitine is an important substance that transports long-chain fatty acids to the mitochondria, where they are broken down and produce energy[5]. This process occurs mainly in organs that use fat as an energy source, such as the heart and skeletal muscles[5]. Humans who eat meat obtain most of their carnitine from food, but approximately 25% of its supply in omnivores comes from the body's own synthesis[5]. In vegetarians and vegans, the formation of carnitine depends on more than 90% of their own production[5]. Endogenous carnitine is produced in the liver and kidneys from two methylated amino acids – lysine and methionine[5]. Scientists have discovered that the mitochondrial transporter SLC25A45 plays a key role in the transfer of trimethyllysine to the mitochondria, where it is converted to hydroxytrimethyllysine, which is essential for the formation of carnitine and subsequently for fat burning[5].