Carnitine
What is it? Overview Usage Side Effects and Warnings
Answers
askAsk

Carnitine Overview

Written by FoundHealth.

Carnitine is a substance used by 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 could in theory improve the ability of certain tissues to produce energy. This has led to the use of carnitine for 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 valproic acid (Depakene) and phenytoin (Dilantin), may reduce carnitine levels; however, whether taking extra carnitine would be helpful has not been determined. 1 2 3 4 5 6 7 8 9 10 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 adult dosages for the diseases described here range from 500 mg to 1,000 mg three times daily. For children, one study used 50 mg/kg twice daily, up to a maximum of 4 g daily. 11 Carnitine is taken in three forms: L-carnitine (for heart and other conditions), propionyl-L-carnitine (for heart conditions), and acetyl-L-carnitine (for Alzheimer's disease). The dosage is the same for all three forms.

What Is the Scientific Evidence for Carnitine?

Angina

Carnitine might be a good addition to standard therapy for angina . In one controlled study, 200 individuals with angina (the exercise-induced variety) took either 2 g daily of L-carnitine or were left untreated. 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. 12 They were also able to reduce the dosages of some of their heart medications (under medical supervision) as their symptoms decreased.

Unfortunately, the results of this study can't be fully trusted because researchers didn't use a double-blind protocol. (For more information on why double-blinding is so important, see Why Does This Database Rely on Double-blind Studies? ) Another trial did use a double-blind, placebo-controlled, design tested L-carnitine in 52 people with angina and found evidence of benefit. 13 In addition, several small studies (some of them double-blind) tested propionyl-L-carnitine for the treatment of angina, and also found evidence of benefit. 14 15 16 17

Intermittent Claudication

People with advanced hardening of the arteries, or atherosclerosis , often have difficulty walking due to lack of blood flow to the legs, a condition called intermittent claudication . 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. 18 A 12-month, double-blind, placebo-controlled trial of 485 patients with intermittent claudication evaluated the potential benefits of propionyl-L-carnitine. 19 Participants with relatively severe disease showed a 44% improvement in walking distance as compared to placebo. However, no improvement was seen in those with mild disease. Another double-blind study followed 245 people and also found benefit. 20 Similar results have been seen in most but not all other studies of L-carnitine or propionyl-L-carnitine. 21 Propionyl-L-carnitine may be more effective for intermittent claudication than plain carnitine.

Congestive Heart Failure

Several small studies have found that carnitine, often in the form of propionyl-L-carnitine, can improve symptoms of congestive heart failure . 22 In one trial, benefits were maintained for 60 days after treatment with carnitine was stopped. 23

After a Heart Attack

L-carnitine has shown inconsistent promise for use after a heart attack .

A double-blind, placebo-controlled study that followed 101 people for 1 month after a heart attack found that use of L-carnitine, in addition to standard care, reduced the size of the infarct (dead heart tissue). 24 In the months following a severe heart attack, the left ventricle of the heart often enlarges, and the pumping action of the heart becomes less efficient. Some evidence suggests that L-carnitine can help prevent heart enlargement, but that it does not improve heart function. In a 12-month, double-blind, placebo-controlled study of 472 individuals who had just undergone a heart attack, use of carnitine at a dose of 6 g/day significantly decreased the rate of heart enlargement. 25 However, heart function was not significantly altered.

A 3-month, double-blind, placebo-controlled study of 60 individuals who had just undergone a heart attack also failed to find improvements in heart function. 26 (Heart enlargement was not studied.)

Results consistent with those of the studies above were seen in a 6-month double blind, placebo-controlled study of 2,330 people who had just had a heart attack. 27 Carnitine failed to produce significant reductions in mortality or heart failure (serious decline in heart function) over the 6-month period. However, the study did find reductions in early death. (Unfortunately, for statistical reasons, the meaningfulness of this last finding is questionable. Reduction in early death was a secondary endpoint rather than a primary one.)

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

Diabetic Neuropathy

High levels of blood sugar can damage the nerves leading to the extremities, causing pain and numbness. This condition is called diabetic peripheral neuropathy . Nerve damage may also develop in the heart, a condition called cardiac autonomic neuropathy. Acetyl-L-carnitine has shown considerable promise for diabetic peripheral neuropathy and some promise for cardiac autonomic neuropathy.

Two 52-week double-blind, placebo-controlled studies, involving a total of 1,257 people with diabetic peripheral neuropathy, evaluated the potential benefits of ALC taken at 500 mg or 1000 mg daily. 28 The results showed that use of ALC, especially at the higher dose, improved sensory perception and decreased pain levels. In addition, the supplement appeared to promote nerve fiber regeneration.

A small study found some potential benefits for cardiac autonomic neuropathy. 29 For more information, including full dosage and safety issues, see the full Carnitine article.

Male Sexual Function

Carnitine has shown promise for improving male sexual function . One double-blind, placebo-controlled study of 120 subjects compared a combination of propionyl-L-carnitine (2 g per day) and acetyl-L-carnitine (2 g per day) against testosterone for the treatment of male aging symptoms (sexual dysfunction, depression, and fatigue). 30 The results indicated that both testosterone and carnitine improved erectile function, mood, and fatigue, as compared to placebo. However, no improvements were seen in the placebo group. This is an unusual occurrence in studies of erectile dysfunction, so it casts some doubt on the study results.

A double-blind study of 40 men evaluated propionyl-L-carnitine (2 g per day) in diabetic men with erectile dysfunction who had not responded well to Viagra. 31 The results indicated that carnitine significantly enhanced the effectiveness of Viagra.

In another double-blind study, a combination of the propionyl and acetyl forms of carnitine enhanced the effectiveness of Viagra in men who suffered from erectile dysfunction caused by prostate surgery. 32

Male Infertility

Growing evidence suggests that L-carnitine or acetyl-L-carnitine or their combination may be helpful for improving sperm quality and function, thereby benefiting male infertility . 33 For example, in one double-blind, placebo-controlled study of 60 men, use of combined L-carnitine (2 g per day) and acetyl-L-carnitine (also at 2 g per day) significantly improved sperm quality. 34

Chronic Obstructive Pulmonary Disease (COPD)

Evidence from three double-blind, placebo-controlled studies enrolling a total of 49 people suggests that L-carnitine can improve exercise tolerance in COPD , presumably by improving muscular efficiency in the lungs and other muscles. 35 36

Alzheimer's Disease

Numerous double- or single-blind 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 and other forms of dementia. 37 However, while early studies found evidence of modest benefit, two large and well-designed studies failed to find acetyl-L-carnitine effective at all.

The first of these was a double-blind, placebo-controlled trial that enrolled 431 participants for 1 year. 38 Overall, acetyl-L-carnitine proved no better than placebo. However, because a close look at the data indicated that the supplement might help people who develop Alzheimer's disease at an unusually young age, researchers performed a follow-up trial. This 1-year, double-blind, placebo-controlled trial evaluated acetyl-L-carnitine in 229 patients with early onset Alzheimer's. 39 Unfortunately, no benefits were seen here either.

One review of the literature concluded that acetyl-L-carnitine may be helpful for mild cases of Alzheimer’s disease, but not more severe cases. 40

Mild Depression

A double-blind study of 60 seniors with dysthymia (a mild form of depression ) found that treatment with 3 g of carnitine daily over a 2-month period significantly improved symptoms as compared to placebo. 41 Positive results were seen in two other studies as well, one of depression and one of dysthymia. 42 43

Hyperthyroidism

Enlargement of the thyroid (goiter) can be due to many causes, including cancer and iodine deficiency. In some cases, thyroid enlargement occurs without any known cause, so-called benign goiter.

Treatment of benign goiter generally consists of taking thyroid hormone pills. This causes the thyroid gland to become less active, and the goiter shrinks. However, there may be undesirable effects as well. Symptoms of hyperthyroidism (too much thyroid hormone) can develop, including heart palpitations, nervousness, weight loss, and bone breakdown.

A double-blind, placebo-controlled trial found evidence that use of L-carnitine could alleviate many of these symptoms. This 6-month study evaluated the effects of L-carnitine in 50 women who were taking thyroid hormone for benign goiter. 44 The results showed that a dose of 2 g or 4 g of carnitine daily protected participants' bones and reduced other symptoms of hyperthyroidism.

Carnitine is thought to affect thyroid hormone by blocking its action in cells. 45 This suggests a potential concern—carnitine might be harmful for people who have low or borderline thyroid levels to begin with. This possibility has not been well explored as yet.

Peyronie’s Disease

Peyronie’s disease is an inflammatory condition of the penis that develops in stages. In the first stage, penile pain occurs with erection; next, the penis becomes curved; finally, erectile dysfunction may occur. Many medications have been tried for Peyronie’s disease, with some success. One such drug is tamoxifen, which is better known as a treatment to prevent breast cancer recurrence. A 3-month, double-blind study compared the effectiveness of acetyl-L-carnitine to the drug tamoxifen in 48 men with Peyronie's disease. 46 Acetyl-L-carnitine (at a dose of 1 g daily) reduced penile curvature while tamoxifen did not; in addition, the supplement reduced pain and slowed disease progression to a greater extent than tamoxifen.

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. 1991;119:799-802.
  2. Chung S, Choi J, Hyun T, Rha Y, Bae C. Alterations in the carnitine metabolism in epileptic children treated with valproic acid. J Korean Med Sci. 12(6):553-8.
  3. Melegh B, Trombitás K. Valproate treatment induces lipid globule accumulation with ultrastructural abnormalities of mitochondria in skeletal muscle. Neuropediatrics. 28(5):257-61.
  4. Zelnik N, Fridkis I, Gruener N. Reduced carnitine and antiepileptic drugs: cause relationship or co-existence? Acta Paediatr. 1995;84:93-95.
  5. Coulter DL. Carnitine deficiency in epilepsy: risk factors and treatment. J Child Neurol. 1995;10(suppl 2):S32-S39.
  6. Melegh B, Pap M, Morava E, Molnar D, Dani M, Kurucz J. Carnitine-dependent changes of metabolic fuel consumption during long-term treatment with valproic acid. J Pediatr. 125(2):317-21.
  7. De Vivo DC, Bohan TP, Coulter DL, Dreifuss FE, Greenwood RS, Nordli DR Jr, Shields WD, Stafstrom CE, Tein I. L-carnitine supplementation in childhood epilepsy: current perspectives. Epilepsia. 39(11):1216-25.
  8. Matsuda I, Ohtani Y. Carnitine status in Reye and Reye-like syndromes. Pediatr Neurol. 2(2):90-4.
  9. Camiña MF, Rozas I, Gómez M, Paz JM, Alonso C, Rodriguez-Segade S. Short-term effects of administration of anticonvulsant drugs on free carnitine and acylcarnitine in mouse serum and tissues. Br J Pharmacol. 103(1):1179-83.
  10. Rodriguez-Segade S, de la Peña CA, Tutor JC, Paz JM, Fernandez MP, Rozas I, Del Río R. Carnitine deficiency associated with anticonvulsant therapy. Clin Chim Acta. 181(2):175-81.
  11. Van Oudheusden LJ, Scholte HR. Efficacy of carnitine in the treatment of children with attention-deficit hyperactivity disorder. Prostaglandins Leukot Essent Fatty Acids. 67(1):33-8.
  12. Cacciatore L, Cerio R, Ciarimboli M, Cocozza M, Coto V, D'Alessandro A, D'Alessandro L, Grattarola G, Imparato L, Lingetti M. The therapeutic effect of L-carnitine in patients with exercise-induced stable angina: a controlled study. Drugs Exp Clin Res. 17(4):225-35.
  13. Cherchi A, Lai C, Angelino F, Trucco G, Caponnetto S, Mereto PE, Rosolen G, Manzoli U, Schiavoni G, Reale A. 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(10):569-72.
  14. Bartels GL, Remme WJ, Pillay M, Schönfeld DH, Kruijssen DA. Effects of L-propionylcarnitine on ischemia-induced myocardial dysfunction in men with angina pectoris. Am J Cardiol. 74(2):125-30.
  15. Bartels GL, Remme WJ, den Hartog FR, et al. Additional anti-ischemic effects of long-term L-propionylcarnitine in anginal patients treated with conventional antianginal therapy. Cardiovasc Drugs Ther. 1995;9:749-753.
  16. Bartels GL, Remme WJ, Holwerda KJ, Kruijssen DA. Anti-ischaemic efficacy of L-propionylcarnitine--a promising novel metabolic approach to ischaemia? Eur Heart J. 17(3):414-20.
  17. Cherchi A, Lai C, Angelino F, Trucco G, Caponnetto S, Mereto PE, Rosolen G, Manzoli U, Schiavoni G, Reale A. 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(10):569-72.
  18. Sabbá C, Berardi E, Antonica G, Ferraioli G, Buonamico P, Godi L, Brevetti G, Albano O. Comparison between the effect of L-propionylcarnitine, L-acetylcarnitine and nitroglycerin in chronic peripheral arterial disease: a haemodynamic double blind echo-Doppler study. Eur Heart J. 15(10):1348-52.
  19. Brevetti G, Diehm C, Lambert D. European multicenter study on propionyl-L-carnitine in intermittent claudication. J Am Coll Cardiol. 34(5):1618-24.
  20. Brevetti G, Perna S, Sabbá C, Martone VD, Condorelli M. Propionyl-L-carnitine in intermittent claudication: double-blind, placebo-controlled, dose titration, multicenter study. J Am Coll Cardiol. 26(6):1411-6.
  21. Bolognesi M, Amodio P, Merkel C, Godi L, Gatta A. 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):417-23.
  22. Cacciatore L, Cerio R, Ciarimboli M, Cocozza M, Coto V, D'Alessandro A, D'Alessandro L, Grattarola G, Imparato L, Lingetti M. The therapeutic effect of L-carnitine in patients with exercise-induced stable angina: a controlled study. Drugs Exp Clin Res. 17(4):225-35.
  23. Löster H, Miehe K, Punzel M, Stiller O, Pankau H, Schauer J. Prolonged oral L-carnitine substitution increases bicycle ergometer performance in patients with severe, ischemically induced cardiac insufficiency. Cardiovasc Drugs Ther. 13(6):537-46.
  24. Singh RB, Niaz MA, Agarwal P, Beegum R, Rastogi SS, Sachan DS. A randomised, double-blind, placebo-controlled trial of L-carnitine in suspected acute myocardial infarction. Postgrad Med J. 72(843):45-50.
  25. Iliceto S, Scrutinio D, Bruzzi P, D'Ambrosio G, Boni L, Di Biase M, Biasco G, Hugenholtz PG, Rizzon P. Effects of L-carnitine administration on left ventricular remodeling after acute anterior myocardial infarction: the L-Carnitine Ecocardiografia Digitalizzata Infarto Miocardico (CEDIM) Trial. J Am Coll Cardiol. 26(2):380-7.
  26. Iyer R, Gupta A, Khan A, Hiremath S, Lokhandwala Y. Does left ventricular function improve with L-carnitine after acute myocardial infarction? J Postgrad Med. 45(2):38-41.
  27. Tarantini G, Scrutinio D, Bruzzi P, Boni L, Rizzon P, Iliceto S. Metabolic treatment with L-carnitine in acute anterior ST segment elevation myocardial infarction. A randomized controlled trial. Cardiology. 106(4):215-23.
  28. Sima AA, Calvani M, Mehra M, Amato A, Acetyl-L-Carnitine Study Group. Acetyl-L-carnitine improves pain, nerve regeneration, and vibratory perception in patients with chronic diabetic neuropathy: an analysis of two randomized placebo-controlled trials. Diabetes Care. 28(1):89-94.
  29. Turpeinen AK, Kuikka JT, Vanninen E, Yang J, Uusitupa MI. Long-term effect of acetyl-L-carnitine on myocardial 123I-MIBG uptake in patients with diabetes. Clin Auton Res. 10(1):13-6.
  30. Cavallini G, Caracciolo S, Vitali G, Modenini F, Biagiotti G. Carnitine versus androgen administration in the treatment of sexual dysfunction, depressed mood, and fatigue associated with male aging. Urology. 63(4):641-6.
  31. Gentile V, Vicini P, Prigiotti G, Koverech A, Di Silverio F. Preliminary observations on the use of propionyl-L-carnitine in combination with sildenafil in patients with erectile dysfunction and diabetes. Curr Med Res Opin. 20(9):1377-84.
  32. Cavallini G, Modenini F, Vitali G, Koverech A. Acetyl-L-carnitine plus propionyl-L-carnitine improve efficacy of sildenafil in treatment of erectile dysfunction after bilateral nerve-sparing radical retropubic prostatectomy. Urology. 66(5):1080-5.
  33. Loumbakis P, Anezinis P, Evangeliou A, et al. Effect of L-carnitine in patients with asthenospermia [abstract]. Eur Urol. 1996;30(suppl 2):255.
  34. Lenzi A, Sgrò P, Salacone P, Paoli D, Gilio B, Lombardo F, Santulli M, Agarwal A, Gandini L. A placebo-controlled double-blind randomized trial of the use of combined l-carnitine and l-acetyl-carnitine treatment in men with asthenozoospermia. Fertil Steril. 81(6):1578-84.
  35. Dal Negro R, Pomari G, Zoccatelli O, et al. L-carnitine and rehabilitative respiratory physiokinesitherapy: metabolic and ventilatory response in chronic respiratory insufficiency. Int J Clin Pharmacol. 1986;24:453-456.
  36. Dal Negro R, Turco P, Pomari C, et al. Effects of L-carnitine on physical performance in chronic respiratory insufficiency. Int J Clin Pharmacol. 1988;26:269-272.
  37. Passeri M, Cucinotta D, Bonati PA, Iannuccelli M, Parnetti L, Senin U. Acetyl-L-carnitine in the treatment of mildly demented elderly patients. Int J Clin Pharmacol Res. 10(1-2):75-9.
  38. Thal LJ, Carta A, Clarke WR, Ferris SH, Friedland RP, Petersen RC, Pettegrew JW, Pfeiffer E, Raskind MA, Sano M, Tuszynski MH, Woolson RF. A 1-year multicenter placebo-controlled study of acetyl-L-carnitine in patients with Alzheimer's disease. Neurology. 47(3):705-11.
  39. Thal LJ, Calvani M, Amato A, Carta A. A 1-year controlled trial of acetyl-l-carnitine in early-onset AD. Neurology. 55(6):805-10.
  40. Montgomery SA, Thal LJ, Amrein R. Meta-analysis of double blind randomized controlled clinical trials of acetyl-L-carnitine versus placebo in the treatment of mild cognitive impairment and mild Alzheimer's disease. Int Clin Psychopharmacol. 18(2):61-71.
  41. Bella R, Biondi R, Raffaele R, Pennisi G. Effect of acetyl-L-carnitine on geriatric patients suffering from dysthymic disorders. Int J Clin Pharmacol Res. 10(6):355-60.
  42. Garzya G, Corallo D, Fiore A, Lecciso G, Petrelli G, Zotti C. Evaluation of the effects of L-acetylcarnitine on senile patients suffering from depression. Drugs Exp Clin Res. 16(2):101-6.
  43. Zanardi R, Smeraldi E. A double-blind, randomised, controlled clinical trial of acetyl-L-carnitine vs. amisulpride in the treatment of dysthymia. Eur Neuropsychopharmacol. 16(4):281-7.
  44. Benvenga S, Ruggeri RM, Russo A, Lapa D, Campenni A, Trimarchi F. Usefulness of L-carnitine, a naturally occurring peripheral antagonist of thyroid hormone action, in iatrogenic hyperthyroidism: a randomized, double-blind, placebo-controlled clinical trial. J Clin Endocrinol Metab. 86(8):3579-94.
  45. Benvenga S, Lakshmanan M, Trimarchi F. Carnitine is a naturally occurring inhibitor of thyroid hormone nuclear uptake. Thyroid. 10(12):1043-50.
  46. Biagiotti G, Cavallini G. Acetyl-L-carnitine vs tamoxifen in the oral therapy of Peyronie's disease: a preliminary report. BJU Int. 88(1):63-7.
 
Share

0 Comments

No one has made any comments yet. Be the first!

Your Comment