• Acetyl-L-Carnitine (ALC), L-Acetyl-Carnitine (LAC), L-Carnitine, Propionyl L-Carnitine
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.
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
The principal dietary sources of carnitine are meat and dairy products, but to obtain therapeutic dosages a supplement is necessary.
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. 73
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.
Carnitine is primarily used for heart-related conditions. Some evidence suggests that it can be used along with conventional treatment for angina
Lesser evidence suggests that it may be helpful for a condition called
Warning: You should not attempt to self-treat any of these serious medical conditions, nor should you use carnitine as a substitute for standard drugs.
Growing, if not entirely consistent, evidence suggests that L-carnitine or acetyl-L-carnitine, or their combination, may be helpful for improving sperm function and thereby provide benefits in male infertility.
Some studies have found evidence that one particular form of carnitine, acetyl-L-carnitine, might be helpful in
Some evidence suggests that carnitine may be useful for improving blood sugar control in people with type 2 (adult-onset)
Much weaker evidence suggests possible benefits for neuropathy caused by the chemotherapy drugs
One small study demonstrated a beneficial effect of L-carnitine on anemia and high cholesterol in patients on hemodialysis for chronic renal failure.
A genetic condition called fragile X syndrome can cause behavioral disturbances such as hyperactivity, along with mental retardation, autism, and alterations in appearance. A preliminary study of 17 boys found that acetyl-L-carnitine might help to reduce hyperactive behavior associated with this condition.
Celiac disease is an autoimmune disease affecting the digestive tract. Fatigue is a common symptom of the disease. One small double-blind trial found evidence that use of L-carnitine at a dose of 2 g daily might help alleviate this symptom.
Other weak evidence suggests that carnitine may be helpful for decreasing the muscle toxicity of AZT (a drug used to treat
Little to no evidence supports other claimed benefits such as treating irregular heartbeat, Down's syndrome, muscular dystrophy, and alcoholic fatty liver disease. However, in a randomized trial involving 25 patients with
What Is the Scientific Evidence for Carnitine?
Carnitine might be a good addition to standard therapy for
. 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.
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
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.
People with advanced hardening of the arteries, or
Similar results have been seen in most but not all other studies of L-carnitine or propionyl-L-carnitine.
Congestive Heart Failure
Several small studies have found that carnitine, often in the form of propionyl-L-carnitine, can improve symptoms of
After a Heart Attack
L-carnitine has shown inconsistent promise for use after a
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).
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.
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.
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.
Note: Carnitine is used along with conventional treatment, not as a substitute for it.
High levels of blood sugar can damage the nerves leading to the extremities, causing pain and numbness. This condition is called
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.
A small study found some potential benefits for cardiac autonomic neuropathy.
For more information, including full dosage and safety issues, see the full
Male Sexual Function
Carnitine has shown promise for improving
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.
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.
Growing evidence suggests that L-carnitine or acetyl-L-carnitine or their combination may be helpful for improving sperm quality and function, thereby benefiting
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.
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
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
The first of these was a double-blind, placebo-controlled trial that enrolled 431 participants for 1 year.
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.
A double-blind study of 60 seniors with dysthymia (a mild form of
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
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.
Carnitine is thought to affect thyroid hormone by blocking its action in cells.
L-carnitine in its three forms appears to be quite safe. However, individuals with low or borderline-low thyroid levels should avoid carnitine because it might impair the action of thyroid hormone. 75
Individuals on dialysis should not receive this (or any other supplement) without a physician's supervision.
The maximum safe dosages for young children, pregnant or nursing women, or those with severe liver or kidney disease have not been established.
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.
14. 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. Cherchi A, Lai C, Angelino F, 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. 1985;23:569-572.
19. Iliceto S, Scrutinio D, Bruzzi P, et al. Effect 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. 1995;26:380-387.
21. 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. 1995;15:417-423.
22. 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. 1992;13:251-255.
24. 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. 1988;77:767-773.
26. Sabba C, Berardi E, Antonica G, et al. 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. 1994;15:1348-1352.
28. Brevetti G, Attisano T, Perna S, et al. Effect of L-carnitine on the reactive hyperemia in patients affected by peripheral vascular disease: a double-blind, crossover study. Angiology. 1989;40:857-862.
33. Pucciarelli G, Mastursi M, Latte S, et al. The clinical and hemodynamic effects of propionyl-L-carnitine in the treatment of congestive heart failure [in Italian; English abstract]. Clin Ter. 1992;141:379-384.
37. 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.
51. Torrioli MG, Vernacotola S, Mariotti P, et al. Double-blind, placebo-controlled study of L-acetylcarnitine for the treatment of hyperactive behavior in fragile X syndrome. Am J Med Genet. 1999;87:366-368.
55. Sorbi S, Forleo P, Fani C, et al. Double-blind, crossover, placebo-controlled clinical trial with L-acetylcarnitine in patients with degenerative cerebellar ataxia. Clin Neuropharmacol. 2000;23:114-118.
57. Benvenga S, Ruggeri RM, Russo A, et al. 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. 2001;86:3579-3594.
61. Vicari E. Effectiveness of a short-term anti-oxidative high-dose therapy on IVF program outcome in infertile male patients with previous excessive sperm. In: International Meeting on Infertility and Assisted Reproductive Technology; Porto Cervo, Italy; June 11-14, 1997.
62. Vicari E, Cerri L, Cataldo T, et al. Effectiveness of single and combined antioxidant therapy in patients with astheno-necrozoospermia from non-bacterial epididymitis: effects after acetyl-carnitine or carnitine-acetyl-carnitine. Presented at: 12th National Conference, Italian Andrology Association; June 9-12, 1999; Copanello, Italy.
67. Semino-Mora MC, Leon-Monzon ME, Dalakas MC. Effect of L-carnitine on the zidovudine-induced destruction of human myotubes. Part I: L-carnitine prevents the myotoxicity of AZT in vitro. Lab Invest. 1994;71:102-112.
70. 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. 2003;18:61-71
72. 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. 2003;18:61-71.
79. Loster H, Miehe K, Punzel M, et al. Prolonged oral L-carnitine substitution increases bicycle ergometer performance in patients with severe, ischemically induced cardiac insufficiency. Cardiovasc Drugs Ther. 1999;13:537-546.
80. Lenzi A, Sgro P, Salacone P, et al. 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. 2004;81:1578-1584.
81. Cavallini G, Caracciolo S, Vitali G, et al. Carnitine versus androgen administration in the treatment of sexual dysfunction, depressed mood, and fatigue associated with male aging. Urology. 2004;63:641-646.
82. Gentile V, Vicini P, Prigiotti G, et al. Preliminary observations on the use of propionyl-L-carnitine in combination with sildenafil in patients with erectile dysfunction and diabetes. Curr Med Res Opin. 2004;20:1377-1384.
83. Sima AA, Calvani M, Mehra M, et al. 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. 2004;28:89-94.
84. Pistone G, Marino A, Leotta C, et al. Levocarnitine administration in elderly subjects with rapid muscle fatigue: effect on body composition, lipid profile and fatigue. Drugs Aging. 2003;20:761-767.
85. Rahbar AR, Shakerhosseini R, Saadat N, et al. Effect of L-carnitine on plasma glycemic and lipidemic profile in patients with type II diabetes mellitus. Eur J Clin Nutr. 2005 Mar 2. [Epub ahead of print]
86. Cavallini G, Ferraretti AP, Gianaroli L, et al. Cinnoxicam and L-carnitine/acetyl-L-carnitine treatment for idiopathic and varicocele-associated oligoasthenospermia. J Androl. 2004;25:761-770; discussion 771-772.
87. Pistone G, Marino A, Leotta C, et al. Levocarnitine administration in elderly subjects with rapid muscle fatigue: effect on body composition, lipid profile and fatigue. Drugs Aging. 2003;20:761-767.
88. Villani RG, Gannon J, Self M, et al. L-Carnitine supplementation combined with aerobic training does not promote weight loss in moderately obese women. Int J Sport Nutr Exerc Metab. 2000;10:199-207.
89. Tarantini G, Scrutinio D, Bruzzi P, et al. Metabolic Treatment with L-Carnitine in Acute Anterior ST Segment Elevation Myocardial Infarction. A Randomized Controlled Trial. Cardiology. 2006 May 9. [Epub ahead of print]
90. Garolla A, Maiorino M, Roverato A, et al. Oral carnitine supplementation increases sperm motility in asthenozoospermic men with normal sperm phospholipid hydroperoxide glutathione peroxidase levels. Fertil Steril. 2005;83:355-361.
91. Balercia G, Regoli F, Armeni T, et al. Placebo-controlled double-blind randomized trial on the use of L-carnitine, L-acetylcarnitine, or combined L-carnitine and L-acetylcarnitine in men with idiopathic asthenozoospermia. Fertil Steril. 2005;84:662-671.
92. Sigman M, Glass S, Campagnone J, et al. Carnitine for the treatment of idiopathic asthenospermia: a randomized, double-blind, placebo-controlled trial. Fertil Steril. 2006 Apr 4. [Epub ahead of print]
93. Cavallini G, Modenini F, Vitali G, et al. Acetyl-L-carnitine plus propionyl-L-carnitine improve efficacy of sildenafil in treatment of erectile dysfunction after bilateral nerve-sparing radical retropubic prostatectomy. Urology. 2005;66:1080-1085.
94. Zanardi R, Smeraldi E. A double-blind, randomised, controlled clinical trial of acetyl-l-carnitine vs. amisulpride in the treatment of dysthymia. Eur Neuropsychopharmacol. 2005 Nov 25. [Epub ahead of print]
97. Stuessi C, Hofer P, Meier C, et al. L: -Carnitine and the recovery from exhaustive endurance exercise: a randomised, double-blind, placebo-controlled trial. Eur J Appl Physiol. 2005 Sep 29. [Epub ahead of print]
98. Tarantini G, Scrutinio D, Bruzzi P, et al. Metabolic Treatment with L-Carnitine in Acute Anterior ST Segment Elevation Myocardial Infarction. A Randomized Controlled Trial. Cardiology. 2006 May 9. [Epub ahead of print]
99. Cavallini G, Modenini F, Vitali G, et al. Acetyl-L-carnitine plus propionyl-L-carnitine improve efficacy of sildenafil in treatment of erectile dysfunction after bilateral nerve-sparing radical retropubic prostatectomy. Urology. 2005;66:1080-1085.
100. Garolla A, Maiorino M, Roverato A, et al. Oral carnitine supplementation increases sperm motility in asthenozoospermic men with normal sperm phospholipid hydroperoxide glutathione peroxidase levels. Fertil Steril. 2005;83:355-361.
101. Balercia G, Regoli F, Armeni T, et al. Placebo-controlled double-blind randomized trial on the use of L-carnitine, L-acetylcarnitine, or combined L-carnitine and L-acetylcarnitine in men with idiopathic asthenozoospermia. Fertil Steril. 2005;84:662-671.
102. Zanardi R, Smeraldi E. A double-blind, randomised, controlled clinical trial of acetyl-l-carnitine vs. amisulpride in the treatment of dysthymia. Eur Neuropsychopharmacol. 2005 Nov 25. [Epub ahead of print]
105. Youle M, Osio M. A double-blind, parallel-group, placebo-controlled, multicentre study of acetyl l-carnitine in the symptomatic treatment of antiretroviral toxic neuropathy in patients with HIV-1 infection. HIV Med. 2007;8:241-250.
106. Rossini M, Di Munno O, Valentini G, et al. Double-blind, multicenter trial comparing acetyl l-carnitine with placebo in the treatment of fibromyalgia patients. Clin Exp Rheumatol. 2007;25:182-188.
108. Malaguarnera M, Cammalleri L, Gargante MP, et al. L-Carnitine treatment reduces severity of physical and mental fatigue and increases cognitive functions in centenarians: a randomized and controlled clinical trial. Am J Clin Nutr. 2007;86:1738-44.
111. Arnold LE, Amato A, Bozzolo H, et al. Acetyl-L-carnitine (ALC) in attention-deficit/hyperactivity disorder: a multi-site, placebo-controlled pilot trial. J Child Adolesc Psychopharmacol. 2007;17:791-802.
Last reviewed April 2009 by EBSCO CAM Review Board
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