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

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

The body needs lysine, methionine, vitamin C, iron, niacin, and vitamin B6 to produce carnitine.

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References:

1. Mancini M, Rengo F, Lingetti M, Sorrentino GP, Nolfe G. Controlled study on the therapeutic efficacy of propionyl-L-carnitine in patients with congestive heart failure. Arzneimittelforschung 1992;42:1101–4.
2. Giamberardino MA et al. Effects of prolonged L-carnitine administration on delayed muscle pain and CK release after eccentric effort. Int J Sports Med 1996;17:320–24.
3. Green RE, Levine AM, Gunning MJ. The effect of L-carnitine supplementation on lean body mass in male amateur body builders. J Am Dietet Assoc 1997;(suppl):A-72.
4. Murray MT. The many benefits of carnitine. Am J Natural Med 1996;3:6–14 [review].
5. Dal Negro R, Pomari G, et al. L-carnitine and rehabilitative respiratory physiokinesitherapy: metabolic and ventilatory response in chronic respiratory insufficiency. Int J Clin Pharmacol Ther Toxicol 1986;24:453–56.
6. Dal Negro R, Turco P, Pomari C, De Conti F. Effects of L-carnitine on physical performance in chronic respiratory insufficiency. Int J Clin Pharmacol Ther Toxicol 1988;26:269–72.
7. Dipalma JR. Carnitine deficiency. Am Family Phys 1988;38:243–51.
8. Kendler BS. Carnitine: an overview of its role in preventive medicine. Prev Med 1986;15:373–90.
9. Del Favero A. Carnitine and gangliosides. Lancet 1988;ii:337 [letter].
10. Kobayashi A, Masumura Y, Yamazaki N. L-carnitine treatment for congestive heart failure--experimental and clinical study. Jpn Circ J 1992;56:86–94.