Carnitine is an amino acid the body uses to turn fat into energy. It is not normally considered an essential nutrient, because the body can manufacture all it needs. However, supplemental carnitine may improve the ability of certain tissues to produce energy. This effect has led to the use of carnitine in various muscle diseases as well as heart conditions. Sources

There is no dietary requirement for carnitine. However, a few individuals have a genetic defect that hinders the body's ability to make carnitine. In addition, diseases of the liver, kidneys, or brain may inhibit carnitine production. Certain medications, especially the antiseizure drugs Depakene (valproic acid) and Dilantin (phenytoin), may reduce carnitine levels; however, whether taking extra carnitine would be helpful has not been determined.1,2,3 Heart muscle tissue, because of its high energy requirements, is particularly vulnerable to carnitine deficiency.

The principal dietary sources of carnitine are meat and dairy products, but to obtain therapeutic dosages a supplement is necessary.

Therapeutic Dosages

Typical dosages for the diseases described here range from 500 to 1,000 mg 3 times daily. Carnitine is taken in three forms: L-carnitine (for heart and other conditions), L-propionyl-carnitine (for heart conditions), and acetyl-L-carnitine (for Alzheimer's disease). The dosage is the same for all three forms.

Therapeutic Uses

Carnitine is primarily used for heart-related conditions. Fairly good evidence suggests that it can be used along with conventional treatment for angina, or chest pain, to improve symptoms and reduce medication needs.4–9 When combined with conventional therapy, it may also reduce mortality after a heart attack.10,11

Lesser evidence suggests that it may be helpful for pain in the legs after walking due to narrowing of the arteries known as intermittent claudication,12–20 as well as congestive heart failure.21–24 Also a few studies suggest that carnitine may be useful for cardiomyopathy.25,26

Warning: You should not attempt to self-treat any of these serious medical conditions, nor should you use carnitine as a substitute for standard heart drugs.

Evidence also suggests that one particular form of carnitine, acetyl-L-carnitine, may be helpful in Alzheimer's disease,27–33 although a recent large study found no benefit.34 This form of carnitine may also be helpful for depression in the elderly.35,36

Weak evidence suggests that carnitine may be able to improve cholesterol and triglyceride levels.37

Carnitine is widely touted as a physical performance enhancer, but there is no real evidence that it is effective and some research indicates that it does not work.38 Little to no evidence supports other claimed benefits such as treating irregular heartbeat, Down's syndrome, muscular dystrophy, impaired sperm motility, chronic obstructive pulmonary disease (emphysema or chronic bronchitis), alcoholic fatty liver disease, and the toxicity of AZT (a drug used to treat AIDS).

What Is the Scientific Evidence for Carnitine?

Angina (Chest Pain)

Carnitine might be a good addition to standard therapy for angina. In one double-blind study, 200 individuals with angina (the exercise-induced variety) took either 2 g daily of L-carnitine or placebo. All the study participants continued to take their usual medication for angina. Those taking carnitine showed improvement in several measures of heart function, including a significantly greater ability to exercise without chest pain.39 They were also able to reduce the dosage of some of their heart medications (under medical supervision) as their symptoms decreased. Similarly positive results were seen in another double-blind trial.40

Other studies using L-propionyl-carnitine have shown similar benefits.41–44

Intermittent Claudication

People with advanced hardening of the arteries, or atherosclerosis, often have difficulty walking due to lack of blood flow to the legs. Pain may develop after walking less than half a block. Although carnitine does not increase blood flow, it appears to improve the muscle's ability to function under difficult circumstances. In a double-blind study of 245 individuals with intermittent claudication, those treated with 2 g daily of L-propionyl-carnitine showed a 73% improvement in walking distance.45 This result is not quite as good as it sounds, because there was a 46% improvement with placebo (the power of suggestion is always amazing!), but it was nonetheless significant.

Similar results have been seen in most but not all other studies.46–53 Interestingly, nearly all the studies on carnitine for this condition have been performed by one investigator. L-propionyl-carnitine seems to be more effective for intermittent claudication than plain carnitine.

For another approach, see the discussion of inositol hexaniacinate in the article on vitamin B3 and the article on ginkgo.

Congestive Heart Failure

Several small studies have found that carnitine, often in the form of L-propionyl-carnitine, can improve symptoms of congestive heart failure.54–57 However, there is better evidence for coenzyme Q10 for treating this condition.

After a Heart Attack

Carnitine may help reduce death rate after a heart attack. In a 12-month, placebo-controlled study, 160 individuals who had experienced a heart attack received 4 g of L-carnitine daily or placebo, in addition to other conventional medication. The mortality rate in the treated group was significantly lower than in the placebo group, 1.2% versus 12.5%, respectively. There were also improvements in heart rate, blood pressure, angina (chest pain), and blood lipids.58 A larger double-blind study of 472 people found that carnitine may improve the chances of survival if given within 24 hours after a heart attack.59

Note: Carnitine is used along with conventional treatment, not as a substitute for it.

Alzheimer's Disease

Numerous double-blind or single-blind clinical studies involving a total of more than 1,400 people have evaluated the potential benefits of acetyl-L-carnitine in the treatment of Alzheimer's disease.60–70 Most have found at least mildly positive results. However, the benefits are slight at most, and one of the best-designed studies found no benefit.

For example, one double-blind trial followed 130 individuals with mild to moderate Alzheimer's disease for 1 full year.71 All participants worsened over that time, but according to 14 different measurements of mental function and behavior, the treated group deteriorated more slowly. However, the difference was not very large, and it was only statistically significant for a few of the rating scales used.

Some studies, however, have not found any benefit. In particular, a recent double-blind placebo-controlled trial that enrolled 431 participants for 1 year found no significant improvement at all in the group treated with acetyl-L-carnitine.72

The most likely explanation for the negative outcome in this well-designed study is that acetyl-L-carnitine produces only a small benefit at most.

Mild Depression

A double-blind study of 60 seniors with mild depression found that treatment with 3 g of carnitine daily over a 2-month period significantly improved symptoms as compared to placebo.73 Positive results were seen in another study as well.74

Performance Enhancement

A 1996 review of clinical studies concluded that no scientific basis exists for the belief that carnitine supplements enhance athletic performance.75 A few studies have found some benefit, but most have not.

Safety Issues

L-carnitine in its three forms appears to be safe, even when taken with medications. Individuals should take care, however, not to use forms of the supplement known as "D-carnitine" or "DL-carnitine," as these can cause angina, muscle pain, and loss of muscle function (probably by interfering with L-carnitine).

The maximum safe dosages for young children, pregnant or nursing women, or those with severe liver or kidney disease have not been established.

Interactions You Should Know About

If you are taking antiseizure medications, particularly valproic acid (Depakote, Depakene) but also phenytoin (Dilantin), you may need extra carnitine.

References

1. Hug C, McGraw CA, Bates SR, et al. Reduction of serum carnitine concentrations during anticonvulsant therapy with phenobarbital, valproic acid, phenytoin, and carbamazepine in children. J Pediatr 119: 799–802, 1991.

2. Chung S, Choi J, Hyun T, et al. Alterations in the carnitine metabolism in epileptic children treated with valproic acid. J Korean Med Sci 12: 553–558, 1997.

3. Melegh B and Trombitas K. Valproate treatment induces lipid globule accumulation with ultrastructual abnormalities of mitochondria in skeletal muscle. Neuropediatrics 28: 257–261, 1997.

4. Cacciatore L, et al. The therapeutic effect of L-carnitine in patients with exercise-induced stable angina: A controlled study. Drugs Exp Clin Res 17: 225–235, 1991.

5. Bartels GL, et al. Effects of L-propionylcarnitine on ischemia-induced myocardial dysfunction in men with angina pectoris. Am J Cardiol 74: 125–130, 1994.

6. Bartels GL, et al. Additional anti-ischaemic effects of long-term L-propionylcarnitine in anginal patients treated with conventional antianginal therapy. Cardiovasc Drugs Ther 9: 749–753, 1995.

7. Bartels GL, et al. Anti-ischemic efficacy of L-propionyl-carnitine—a promising novel metabolic approach to ischaemia? Eur Heart J 17: 414–420, 1996.

8. Cherchi A, et al. Effects of L-carnitine on exercise tolerance in chronic, stable angina: A multicenter, double-blind, randomized, placebo controlled crossover study. Int J Clin Pharmacol Ther Toxicol 23: 569–572, 1985.

9. Lagioia R, et al. Propionyl-L-carnitine: A new compound in the metabolic approach to the treatment of effort angina. Int J Cardiol 34: 167–172,1992.

10. Davini P, Bigalli A, Lamanna F, and Boem A. Controlled study on L-carnitine therapeutic efficacy in post-infarction. Drugs Exp Clin Res 18(8): 355–365, 1992.

11. Iliceto S, et al. Effect of L-carnitine administration on left ventricular remodeling after acute anterior myocardial infarction: the L-Carnitine Echocardiografia Digitalizzata Infarto Miocardico (CEDIM) trial. J Am Coll Cardiol 26: 380–387, 1995.

12. Brevetti G, et al. Propionyl-L-carnitine in intermittent claudication: Double-blind, placebo-controlled, dose titration, multicenter study. J Am Coll Cardiol 26(6): 1411–1416, 1995.

13. Bolognesi M, Amodio P, Merkel C, et al. Effect of 8-day therapy with propionyl-L-carnitine on muscular and subcutaneous blood flow of the lower limbs in patients with peripheral arterial disease. Clin Physiol 15(5): 417–423, 1995.

14. Brevetti G, Perna S, Sabba C, et al. Superiority of L-propionylcarnitine vs L-carnitine in improving walking capacity in patients with peripheral vascular disease: an acute, intravenous, double-blind, cross-over study. Eur Heart J 13(2): 251–255, 1992.

15. Greco AV, Mingrone G, Bianchi M, and Ghirlanda G. Effect of propionyl-L-carnitine in the treatment of diabetic angiopathy: controlled double-blind trial versus placebo. Drugs Exp Clin Res 18(2): 69–80, 1992.

16. Brevetti G, Chiariello M, Ferulano G, et al. Increases in walking distance in patients with peripheral vascular disease treated with L-carnitine: A double-blind, cross-over study. Circulation 77(4): 767–773, 1988.

17. Deckert J. Propionyl-L-carnitine for intermittent claudication. J Fam Pract 44(6): 533–534, 1997.

18. Sabba C, Berardi E, Antonica G, et al. Comparison between the effect of L-propionylcarnitine, L-carnitine and nitroglycerin in chronic peripheral arterial disease: a haemodynamic double-blind echo-doppler study. Eur Heart J 15: 1348–1352, 1994.

19. Pepine CJ. The therapeutic potential of carnitine in cardiovascular disorders. Clin Ther 13(1): 2–21, 1991.

20. Brevetti G, et al. Effect of L-carnitine on the reactive hyperemia in patients affected by peripheral vascular disease: a double-blind, crossover study. Angiology 40(10): 857–862, 1989.

21. Caponetto S, et al. Efficacy of L-propionylcarnitine treatment in patients with left ventricular dysfunction. Eur Heart J 15: 1267–1273, 1994.

22. Mancini M, et al. Controlled study on the therapeutic efficacy of propionyl-L-carnitine in patients with congestive heart failure. Arzneimittelforschung 42: 1101–1104, 1992.

23. Pucciarelli G, et al. The clinical and hemodynamic effects of propionyl-L-carnitine in patients with congestive heart failure. Clin Ther 141: 379–384, 1992.

24. Cacciatore L, et al. The therapeutic effect of L-carnitine in patients with exercise-induced stable angina: A controlled study. Drugs Exp Clin Res 17: 225–235, 1991.

25. Winter S, Jue K, Prochazka J, et al. The role of L-carnitine in pediatric cardiomyopathy. J Child Neurol (Canada) 10(Suppl. 2): 2S45–2S51, 1995.

26. Pepine CJ. The therapeutic potential of carnitine in cardiovascular disorders. Clin Ther 13(1): 2–21, 1991.

27. Passeri M, et al. Acetyl-L-carnitine in the treatment of mildly demented elderly patients. Int J Clin Pharmacol Res 10: 75–79, 1990.

28. Calvani M, et al. Action of acetyl-L-carnitine in neurodegeneration and Alzheimer's disease. Ann N Y Acad Sci 663: 483–486, 1992.

29. Sano M, et al. Double-blind parallel design pilot study of acetyl-levocarnitine in patients with Alzheimer's disease. Arch Neurol 49: 1137–1141, 1992.

30. Spagnoli A, et al. Long-term acetyl-L-carnitine treatment in Alzheimer's disease. Neurology 41: 1726–1732, 1991.

31. Campi N, et al. Selegiline versus L-acetylcarnitine in the treatment of Alzheimer-type dementia. Clin Ther 12: 306–314, 1990.

32. Vecchi GP, et al. Acetyl-L-carnitine treatment of mental impairment in the elderly: Evidence from a multicenter study. Arch Gerontol Geriatr 2(Suppl): 159–168, 1991.

33. Bonavita E. Study of the efficacy and tolerability of L-acetylcarnitine therapy in the senile brain. Int J Clin Pharmacol Ther Toxicol 24: 511–516, 1986.

34. Thal LJ, Carta A, Clarke WR, et al. A 1-year multicenter placebo-controlled study of acetyl-L-carnitine in patients with Alzheimer's disease. Neurology 47: 705–711, 1996.

35. Bella R, Biondi R, Raffaele R, and Pennisi G. Effect of acetyl-L-carnitine on geriatric patients suffering from dysthymic disorders. Int J Clin Pharmacol Res 10: 355–360, 1990.

36. Garzya G, et al. Evaluation of the effects of L-acetylcarnitine on senile patients suffering from depression. Drugs Exp Clin Res 16: 101–106, 1990.

37. Davini P, Bigalli A, Lamanna F, and Boem A. Controlled study on L-carnitine therapeutic efficacy in post-infarction. Drugs Exp Clin Res 18(8): 355–365, 1992.

38. Heinonen OJ. Carnitine and physical exercise. Sports Med 22(2): 109–132, 1996.

39. Cacciatore L, et al. The therapeutic effect of L-carnitine in patients with exercise-induced stable angina: A controlled study. Drugs Exp Clin Res 17: 225–235, 1991.

40. Cherchi A, et al. Effects of L-carnitine on exercise tolerance in chronic, stable angina: A multicenter, double-blind, randomized, placebo-controlled crossover study. Int J Clin Pharmacol Ther Toxicol 23: 569–572, 1985.

41. Bartels GL, et al. Effects of L-propionylcarnitine on ischemia-induced myocardial dysfunction in men with angina pectoris. Am J Cardiol 74: 125–130, 1994.

42. Bartels GL, et al. Additional anti-ischemic effects of long-term L-propionylcarnitine in anginal patients treated with conventional antianginal therapy. Cardiovasc Drugs Ther 9: 749–753, 1995.

43. Bartels GL, et al. Anti-ischaemic efficacy of L-propionyl-carnitine—a promising novel metabolic approach to ischaemia? Eur Heart J 17: 414–420, 1996.

44. Lagioia R, et al. Propionyl-L-carnitine: A new compound in the metabolic approach to the treatment of effort angina. Int J Cardiol 34: 167–172, 1992.

45. Brevetti G, et al. Propionyl-L-carnitine in intermittent claudication: Double-blind, placebo-controlled, dose titration, multicenter study. J Am Coll Cardiol 26(6): 1411–1416, 1995.

46. Bolognesi M, Amodio P, Merkel C, et al. Effect of 8-day therapy with propionyl-L-carnitine on muscular and subcutaneous blood flow of the lower limbs in patients with peripheral arterial disease. Clin Physiol 15(5): 417–423, 1995.

47. Brevetti G, Perna S, Sabba C, et al. Superiority of L-propionylcarnitine vs L-carnitine in improving walking capacity in patients with peripheral vascular disease: an acute, intravenous, double-blind, cross-over study. Eur Heart J 13(2): 251–255, 1992.

48. Greco AV, Mingrone G, Bianchi M, and Ghirlanda G. Effect of propionyl-L-carnitine in the treatment of diabetic angiopathy: controlled double-blind trial versus placebo. Drugs Exp Clin Res 18(2): 69–80, 1992.

49. Brevetti G, Chiariello M, Ferulano G, et al. Increases in walking distance in patients with peripheral vascular disease treated with L-carnitine: A double-blind, cross-over study. Circulation 77(4): 767–773, 1988.

50. Deckert J. Propionyl-L-carnitine for intermittent claudication. J Fam Pract 44(6): 533–534, 1997.

51. Sabba C, Berardi E, Antonica G, et al. Comparison between the effect of L-propionylcarnitine, L-carnitine and nitroglycerin in chronic peripheral arterial disease: a haemodynamic double-blind echo-doppler study. Eur Heart J 15: 1348–1352, 1994.

52. Pepine CJ. The therapeutic potential of carnitine in cardiovascular disorders. Clin Ther 13(1): 2–21, 1991.

53. Brevetti G, et al. Effect of L-carnitine on the reactive hyperemia in patients affected by peripheral vascular disease: a double-blind, crossover study. Angiology 40(10): 857–862, 1989.

54. Caponetto S, et al. Efficacy of L-propionylcarnitine treatment in patients with left ventricular dysfunction. Eur Heart J 15: 1267–1273, 1994.

55. Mancini M, et al. Controlled study on the therapeutic efficacy of propionyl-L-carnitine in patients with congestive heart failure. Arzneimittelforschung 42: 1101–1104, 1992.

56. Pucciarelli G, et al. The clinical and hemodynamic effects of propionyl-L-carnitine in patients with congestive heart failure. Clin Ther 141: 379–384, 1992.

57. Cacciatore L, et al. The therapeutic effect of L-carnitine in patients with exercise-induced stable angina: A controlled study. Drugs Exp Clin Res 17: 225–235, 1991.

58. Davini P, Bigalli A, Lamanna F, and Boem A. Controlled study on L-carnitine therapeutic efficacy in post-infarction. Drugs Exp Clin Res 18(8): 355–365, 1992.

59. Iliceto S, et al. Effect of L-carnitine administration on left ventricular remodeling after acute anterior myocardial infarction: the L-Carnitine Echocardiografia Digitalizzata Infarto Miocardico (CEDIM) trial. J Am Coll Cardiol 26: 380–387, 1995.

60. Calvani M, et al. Action of acetyl-L-carnitine in neurodegeneration and Alzheimer's disease. Ann N Y Acad Sci 663: 483–486, 1992.

61. Cipolli C, et al. Effects of L-acetylcarnitine on mental deterioration in the aged: Initial results. Clin Ther 132: 479–510, 1990.

62. Passeri M, et al. Acetyl-L-carnitine in the treatment of mildly demented elderly patients. Int J Clin Pharmacol Res 10: 75–79, 1990.

63. Salvioli G and Neri M. L-acetylcarnitine treatment of mental decline in the elderly. Drugs Exp Clin Res 20: 169–176, 1994.

64. Spagnoli A, et al. Long-term acetyl-L-carnitine treatment in Alzheimer's disease. Neurology 41: 1726–1732, 1991.

65. Vecchi GP, et al. Acetyl-L-carnitine treatment of mental impairment in the elderly: Evidence from a multicenter study. Arch Gerontol Geriatr 2(Suppl): 159–168, 1991.

66. Thal LJ, Carta A, Clarke WR, et al. A 1-year multicenter placebo-controlled study of acetyl-L-carnitine in patients with Alzheimer's disease. Neurology 47: 705–711, 1996.

67. Campi N, et al. Selegiline versus L-acetylcarnitine in the treatment of Alzheimer-type dementia. Clin Ther 12: 306–314, 1990.

68. Sano M, et al. Double-blind parallel design pilot study of acetyl-levocarnitine in patients with Alzheimer's disease. Arch Neurol 49: 1137–1141, 1992.

69. Rai G, et al. Double-blind, placebo-controlled study of acetyl-l-carnitine in patients with Alzheimer's dementia. Curr Med Res Opin 11: 638–647, 1990.

70. Bonavita E. Study of the efficacy and tolerability of L-acetylcarnitine therapy in the senile brain. Int J Clin Pharmacol Ther Toxicol 24: 511–516, 1986.

71. Spagnoli A, et al. Long-term acetyl-L-carnitine treatment in Alzheimer's disease. Neurology 41: 1726–1732, 1991.

72. Thal LJ, Carta A, Clarke WR, et al. A 1-year multicenter placebo-controlled study of acetyl-L-carnitine in patients with Alzheimer's disease. Neurology 47: 705–711, 1996.

73. Bella R, Biondi R, Raffaele R, and Pennisi G. Effect of acetyl-L-carnitine on geriatric patients suffering from dysthymic disorders. Int J Clin Pharmacol Res 10: 355–360, 1990.

74. Garzya G, et al. Evaluation of the effects of L-acetylcarnitine on senile patients suffering from depression. Drugs Exp Clin Res 16: 101–106, 1990.

75. Heinonen OJ. Carnitine and physical exercise. Sports Med 22(2): 109–132, 1996.

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