L-Carnitine is not an amino acid in the strict sense, but it bears similarity to amino acids and is usually grouped under that heading. It is also a vitamin-like nutrient related to the B vitamins. L-Carnitine is used by the body to transport long chain fatty acids to the mitochondria in your cells, where it is burned for energy. Since this fat burning is such a major source of muscular energy, deficiencies in carnitine are manifested as low energy levels and muscular weakness. They can also appear as mental confusion or cloudiness, angina (heart pain) and weight gain.

Carnitine can be manufactured in the body provided the necessary vitamins and minerals are present. These include vitamin B1, B6, C, and iron. The amino acids lysine and methionine are also needed. Carnitine is present in meat, particularly beef, sheep, and lamb. Other animal foods such as milk, cheese, and poultry contain somewhat less carnitine. The available research on L-carnitine supplementation does not appear to support claims of enhanced aerobic or anaerobic exercise performance.

Carnitine supplementation can help prevent fatty build-up in the heart and liver (especially likely if you are a regular consumer of alcoholic beverages).