What does it do? L-carnitine is made in the body from the amino acids lysine and methionine. It is needed to release energy from fat. Its actions appear to be particularly important in the heart. For congestive heart failure, much of the research has used a modified form of carnitine called propionyl-L-carnitine (PC). In one double blind trial, using 500 mg PC per day led to a 26% increase in exercise capacity after six months.1

Research shows that individuals who supplement with carnitine while engaging in an exercise regimen are less likely to experience muscle soreness.2 However, the belief that carnitine’s effect on energy release will help build muscle or improve athletic performance has, so far, not been supported by most research.3 4

L-Carnitine work quickly in encouraging the body to burn stored fat for energy rather than carbohydrates. It does this by forcing fat into the muscular cells.

However, carnitine has been given to people with chronic lung disease in trials investigating how the body responds to exercise.5 6 In these double blind reports, 2 grams of carnitine taken twice per day for two to four weeks led to positive changes in breathing response to exercise.

Where is it found? Dairy and red meat contain the greatest amounts of carnitine. Therefore, people who have a limited intake of meat and dairy products tend to have lower carnitine intakes.

Who is likely to be deficient? L-Carnitine deficiencies are rare, even in strict vegetarians, because the body produces carnitine relatively easily.

Rare genetic diseases can cause a carnitine deficiency. Also, deficiencies are occasionally associated with other diseases, such as diabetes and cirrhosis.7 8 A carnitine deficiency can also result from oxygen deprivation which can occur in some heart conditions. In Italy, carnitine is prescribed for heart failure, heart arrhythmias, angina pectoris, and lack of oxygen to the heart.9

Carnitine and Athletes. As a athlete, you know performance centers on your body’s ability to produce explosive energy. And since fat provides the main energy fuel for muscles, tapping into your body’s fat stores is critical. That’s where carnitine come in. Playing a key role in fat oxidation, caritine "shuttles" or transports long-chair fatty acids (the highest energy food ) across the mitochondrial membrane (the power plant of the cell) for enhanced energy production. Without it, fats cannot burned for energy; they are instead stored in the body as fats and triglycerides. Carnitine work quickly in encouraging the body to burn stored fat for energy rather than carbohydrates. It does this by forcing fat into the muscular cells.

90% of carnitine is located in skeletal and cardiac muscle cells. A deficiency can seriously impair the normal functioning of the heart and muscles. This is particularly true among vegetarians, who are more likely to experience carntine deficiency. The reason for this is simple: carnitine is most abundant in meats and milk. Thus, vegetarians could benefit immensely from supplementation.

 According to several studies, carnitine supplementation resulted in significant improvements in cardiovascular function after exercise in several double-bline studies among athletes and normal subjects alike. Moreover, carnitine can improve exercise intensity and endurance through fat oxidation and by reducing blood lactic acid levels.

How much is usually taken? Most people do not need carnitine supplements. For therapeutic use, typical amounts are 1–3 grams per day.

It remains unclear whether the propionyl-L-carnitine form of carnitine used in congestive heart failure research has greater benefits than the L-carnitine form, since limited research in both animals and humans with the more common L-carnitine has also shown very promising effects.10

Are there any side effects or interactions? L-carnitine has not been consistently linked with any toxicity.

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