Carnitine is a water-soluble vitamin-like compound that promotes the transport of long-chain fatty acids to mitochondria.
There are generally two forms, L-carnitine and D-carnitine. L-carnitine is the physiologically active form in the body, and in the following, carnitine mainly refers to L-carnitine.
Carnitine is not an essential nutrient and can be formed in the liver from other nutrients - mainly two amino acids, lysine, and methionine.
In addition, carnitine is also found in high levels in animal foods. Meat products, especially beef and pork are good sources of carnitine; fish and poultry have less of it, and dairy products have even lower levels.
Carnitine has several metabolic functions in muscle cells, so the theory is that carnitine supplementation can enhance physical performance and reduce weight.
Carnitine is generally considered a less effective supplement, possibly because it is difficult to increase. More research is needed on ways to increase muscle carnitine.