L-Carnitine

Also indexed as: Propionyl-L-Carnitine

What does it do? L-carnitine is needed to release energy from fat. It transports fatty acids into mitochondria, the powerhouses of cells. L-carnitine is made in the body from the amino acids, lysine and methionine. However, in infancy and in situations of high energy needs, such as pregnancy and breast-feeding, the need for L-carnitine can exceed production by the body. Therefore, L-carnitine is considered a “conditionally essential” nutrient.1

L-carnitine’s actions appear to be particularly important in the heart. As an example, patients with diabetes and high blood pressure were given 4 grams of L-carnitine per day in an preliminary study.2 After 45 weeks, irregular heartbeat and abnormal heart functioning decreased significantly compared to nonsupplemented patients. 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.3 In other research, patients with congestive heart failure given 1.5 grams PC daily for 15 days had a 21% increase in exercise tolerance and a 45% increase in oxygen consumption.4

Research shows that people who supplement with L-carnitine while engaging in an exercise regimen are less likely to experience muscle soreness.5 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.6 7 In a double-blind study of trained athletes, supplementation with 2 grams of L-carnitine two hours before and after a 20 km run failed to improve physical performance or exercise recovery.8

However, L-carnitine has been given to people with chronic lung disease in trials investigating how the body responds to exercise.9 10 In these double-blind reports, 2 grams of L-carnitine taken twice per day for two to four, weeks led to positive changes in lung function and metabolism during exercise.

Beta thalassemia major is an inherited, fatal form of anemia commonly seen in people of Mediterranean descent. People with beta thalassemia major invariably require blood transfusions, which can eventually result in iron overload.11 L-carnitine stabilizes red blood cells and supplementation may decrease the need for blood transfusions. In a preliminary study, children with beta thalassemia major who took 100 mg of L-carnitine per 2.2 pounds of body weight per day for three months, had a significantly decreased need for blood transfusions.12

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 L-carnitine intakes.

L-carnitine has been used in connection with the following conditions (refer to the individual health concern for complete information):

Rating Health Concerns
3Stars Angina
Congestive heart failure (propionyl-L-carnitine)
Heart attack
Intermittent claudication (propionyl-L-carnitine)
2Stars Anemia (for thalassemia)
Chronic fatigue syndrome
Chronic obstructive pulmonary disease (COPD)
Diabetes
High triglycerides
Infertility (male)
Intermittent claudication (L-carnitine)
Sprains and strains (for preventing exercise-related muscle injury)
1Star Athletic performance (for ultra-endurance only)
Beta thalassemia major
Cardiomyopathy (only for children with inherited cardiomyopathy)
High cholesterol
Liver cirrhosis
Mitral valve prolapse
Raynaud’s disease
Weight loss
3Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star An herb is primarily supported by traditional use, or the herb or supplement has little scientific support and/or minimal health benefit.

Who is likely to be deficient? 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.13 14 Among people with diabetes, carnitine deficiency is more likely to be found in persons experiencing complications of diabetes (such as retinopathy, hyperlipidemia, or neuropathy), suggesting that carnitine deficiency may play a role in the development of these complications.15 A carnitine deficiency can also result from oxygen deprivation which can occur in some heart conditions. In Italy, L-carnitine is prescribed for heart failure, heart arrhythmias, angina, and lack of oxygen to the heart.16

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.17

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

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

Are there any drug interactions? Certain medications may interact with L-carnitine. Refer to the drug interactions safety check for a list of those medications.

References:

1. Giovannini M, Agostoni C, Salari PC. Is carnitine essential in children? J Int Med Res 1991;19:88–102.

2. Digiesi V, Palchetti R, Cantini F. The benefits of L-carnitine in essential arterial hypertension. Minerva Med 1989;80:227–31.

3. Mancini M, Rengo F, Lingetti M, et al. Controlled study on the therapeutic efficacy of propionyl-L-carnitine in patients with congestive heart failure. Arzneimittelforschung 1992;42:1101–4.

4. Anand I, Chandrashenkhan Y, De Giuli F, et al. Acute and chronic effect of propionyl-L-carnitine on the hemodynamics, exercise capacity and hormones of patients with congestive heart failure. Cardiovasc Drugs Ther 1998;12:291–9.

5. Giamberardino MA, Dragani L, Valente R, et al. Effects of prolonged L-carnitine administration on delayed muscle pain and CK release after eccentric effort. Int J Sports Med 1996;17:320–4.

6. Green RE, Levine AM, Gunning MJ. The effect of L-carnitine supplementation on lean body mass in male amateur body builders. J Am Diet Assoc 1997;(suppl):A–72.

7. Murray MT. The many benefits of carnitine. Am J Natural Med 1996;3:6–14 [review].

8. Columbani P, Wenk C, Kunz I, et al. Effect of L-carnitine supplementation on physical performance and energy metabolism of endurance-trained athletes: a double blind crossover field study. Eur J Appl Physiol 1996;73:434–9.

9. Dal Negro R, Pomari G, Zoccatelli O, Turco P. L-carnitine and rehabilitative respiratory physiokinesitherapy: metabolic and ventilatory response in chronic respiratory insufficiency. Int J Clin Pharmacol Ther Toxicol 1986;24:453–6.

10. 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.

11. Beers MH, Berkow R (eds). The Merck Manual of Diagnosis and Therapy, 17th ed. Whitehouse Station, NJ: Merck and Co., Inc, 1999, 881–3.

12. Yesilipek MA, Hazar V, Yegin O. L-Carnitine treatment in beta thalassemia major. Acta Haematol 1998;100:162–3.

13. Dipalma JR. Carnitine deficiency. Am Fam Physician 1988;38:243–51.

14. Kendler BS. Carnitine: an overview of its role in preventive medicine. Prev Med 1986;15:373–90.

15. Tamamogullari N, Silig Y, Icagasioglu S, Atalay A. Carnitine deficiency in diabetes mellitus complications. J Diabetes Complications 1999;13:251–3.

16. Del Favero A. Carnitine and gangliosides. Lancet 1988;2:337 [letter].

17. Kobayashi A, Masumura Y, Yamazaki N. L-carnitine treatment for congestive heart failure—experimental and clinical study. Jpn Circ J 1992;56:86–94.