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Supplements

L-carnitine

What Is It?
Health Benefits
Forms
Dosage Information
Guidelines for Use
General Interaction
Possible Side Effects
Cautions
References
Evidence Based Rating Scale


What Is It?

Carnitine is an amino acid-like compound that helps the body produce energy. While readily abundant in meats and dairy foods, some people take L-carnitine in supplement form to increase vitality. L-carnitine transports fatty acids to the "factory" portion of cells, which then convert the Fat into energy that the heart, muscles, and other body tissues can use.

L-carnitine supplements are particularly valuable for people with conditions that can interfere with its absorption, including various liver and kidney problems, metabolic stress, long-term alcohol use, and in some cases, a high-fat diet. So check with your doctor if you have any concerns. A simple urine test can determine if you have an L-carnitine deficiency.

Without enough L-carnitine to move fatty acids to the right place, your body will eventually wear down, and you may feel drained and tired. You may also experience muscle pain, weakness, low blood pressure, and/or confusion, as well as chest pain.

Health Benefits

L-carnitine plays a critical role in metabolizing a number of other important substances as well, which helps to explain why it holds promise for so many disorders.

Specifically, L-carnitine may help to:

Treat heart conditions. The heart in particular is highly dependent on L-carnitine, and taking it in supplement form is currently being explored as an option for speeding recovery after a heart attack, as well as for treating Angina (chest pain), arrhythmia (irregular heartbeats), and Congestive Heart Failure. 

Several studies indicate taking L-carnitine orally after a heart attack reduces complications and mortality. (1-3) In a 1992 Italian study, 81 male and female patients out of 160 studied received L-carnitine supplementation for a year. During the 12 months, the 81 treated patients showed decreased mortality, improvements in heart rate and blood pressure, and a decrease in anginal attacks, rhythm disorders, and in clinical signs of impaired myocardial contractility. The control group, which did not receive L-carnitine, showed an increased incidence of sudden death and of deaths caused by reinfarction. (3) Early studies also indicate taking L-carnitine orally improves exercise tolerance in patients with chronic stable angina, and improves symptoms in patients with Congestive Heart Failure. (4-7)

Boost immune response in HIV patients. Some studies indicate that L-carnitine  may improve endurance in those weakened by disease, and boost an immune response in people who are HIV-infected. It is often used intravenously to improve CD4 cell counts in people with HIV/AIDS. (8, 9)

Aid memory loss. A form of carnitine that is produced naturally in the brain and increases memory-enhancing brain chemicals--acetyl-L-carnitine, or ALC--is currently being studied in supplement form as a possible treatment for memory loss associated with aging and Alzheimer's disease. However, preliminary evidence is conflicting. A 2003 review of Alzheimer’s patients treated with ALC reported only nominal advantages compared to placebo groups over a range of memory tests. (10)

Enhance athletic performance. Studies are conflicting regarding the effectiveness of L-carnitine for enhancing athletic performance by improving energy and fat metabolism. A positive effect appears most pronounced for endurance-related events, such as cycling and long distance running. Although some studies show that L-carnitine supplementation increases maximum oxygen uptake and power output (11, 12), there is no evidence that supplementation will enhance athletic endurance. A small 2007 study of 28 Korean athletes who received L-carnitine supplementation for six weeks found the treatment did not increase fat metabolism and would be, therefore, unlikely to be associated with enhanced exercise performance. (13)

Treat kidney disease. Because much of the body’s carnitine is produced in the kidney, those with end-stage renal disease (ESRD) can have a significant carnitine deficiency, particularly those undergoing hemodialysis. L-carnitine is FDA-approved for ESRD patients for the prevention and treatment of L-carnitine deficiency where it has been found to improve red blood cell count and hemoglobin levels during hemodialysis. (16)

Treat lyme disease. Because L-carnitine helps turn food into useable energy, it may help battle the fatigue that accompanies Lyme disease, an inflammatory disease spread by ticks.

Increase fertility in men. Several studies have shown that L-carnitine helped increase sperm counts and motility in men with infertility. A 2004 placebo-controlled, double-blind randomized trial of 60 infertile Italian men aged 20 to 40 found the most significant increase in sperm motility was present in the group that received treatment of L-carnitine and ALC. (17)

Control your weight. Some evidence indicates L-carnitine may be helpful in burning fat, when combined with a regular exercise program. However, more research is needed in this area.

Reduce symptoms of Hyperthyroidism. L-carnitine has been shown to effectively reduce symptoms of hyperthyroidism. The mechanism of action of L-carnitine has been extensively studied, in animals since the 1960s and more recently in humans. These studies have shown that the effects of L-carnitine in hyperthyroidism are a result of activity in the cells rather than in the thyroid gland itself. By blocking entry of excess thyroid hormone into the cell nucleus of liver cells (where T4 is converted to the excess T3 associated with hyperthyroidism), L-carnitine seems to reduce symptoms of Graves’ disease, including nervousness, heat tolerance, insomnia, emotional instability, tremors, and excessive sweating. A 2001 Italian randomized, double-blind, placebo-controlled six-month trial of 50 women with hyperthyroidism evaluated whether 2 or 4 g of L-carnitine daily could prevent and/or minimize nine hyperthyroidism-related symptoms. Benefits of L-carnitine became evident within the second week of treatment, including reduction of goiter size, I-131 uptake, liver enzyme levels, and an improvement in eye symptoms including exopthalmos. Supplementation of L-carnitine also had a beneficial effect on muscle function, strength, and bone mineralization. (14) And in a 2004 review of the prior clinical study as well as previous experiments on cells, confirmed the effect of L-carnitine in inhibiting transport of T4 and T3 into the cell nuclei, validating its potential efficacy in moderating hyperthyroidism. (15)

Forms       

  • Tablet 
  • Liquid

    *On supplement labels, Amino acids are often prefaced with the letter L or the letter D. Purchase only the L-carnitine form, since it most resembles the carnitine produced naturally by the body. 

    Dosage Information

  • Chronic stable angina/congestive heart failure: 500 to 1,000 mg a day

  • For deficiencies in adults: 990 mg tablet two to three times a day.

  • Fat metabolism: 1,000 to 2,000 mg daily, divided into two doses.

  • Following heart attack: 2 to 6 grams daily.

  • Kidney disease/hemodialysis: 2 to 4 grams daily, in divided doses.

    Guidelines for Use

    Individuals taking L-carnitine to boost fat metabolism should stop using it for at least one week each month.

    General Interaction

    Possible interactions with warfarin (Coumadin) and with thyroid hormones. 

    Possible Side Effects

  •    L-carnitine has been associated with nausea, vomiting, abdominal cramps, heartburn, gastritis, diarrhea, body odor, and seizures in some people. One of its metabolites can cause the urine, breath, and sweat to have a fishy odor.

  •    D-carnitine supplements should be avoided because they interfere with the natural form of L-carnitine and can cause undesirable side effects.

    Cautions

  •    High doses (5 or more grams daily) can cause diarrhea.

  •    If used by persons taking warfarin (Coumadin) or thyroid supplementation, tests to detect alterations in blood medication levels should be performed.

     References

    1. Singh RB, Niaz MA, Agarwal P, et al. A randomized, double-blind, placebo-controlled trial of L-carnitine in suspected acute myocardial infarction. Postgrad Med J. 1996; 72:45-50.

    2. Lliceto S, Scrutinio D, Bruzzi P, et al. 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. 1995;26:380-7.

    3. Davini P, Bigalli A, Lamanna F, Boem A. Controlled study on L-carnitine therapeutic efficacy in post-infarction. Drugs Exp Clin Res. 1992;18:355-65.

    4. Cacciatore L, Cerio R, Ciarimboli M, et al. The therapeutic effect of L-carnitine in patients with exercise-induced stable angina: a controlled study. Drugs Exp Clin Res. 1991;17:225-35.

    5. 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;23:569-72.

    6. Rizos I. Three-year survival of patients with heart failure caused by dilated cardiomyopathy and L-carnitine administration. Am Heart J. 2000; 139:S120-3.

    7. Ghidini O, Azzurro M, Vita G, Sartori G. Evaluation of the therapeutic efficacy of L-carnitine in congestive heart failure. Int J Clin Pharmacol Ther Toxicol. 1988;26:217-20.

    8. Famularo G, De Simone C, Trinchieri V, Mosca L. Carnitines and its congeners: a metabolic pathway to the regulation of immune response and inflammation. Ann NY Acad Sci. 2004 Nov;1033:132-8.

    9. De Simone C, Famularo G, Tzantzoglou S, Trinchieri V, et al. Carnitine depletion in peripheral blood mononuclear cells from patients with AIDS: effect of oral L-carnitine. AIDS. 1994 May; 8(5):655-60.

    10. McDaniel MA, Maier SF, Einstein GO. “Brain-specific” nutrients: a memory cure? Nutrition. 2003 Nov-Dec;19(11-12):957-75.

    11. Vecchiet L, Di Lisa F, Pieralisi G, et al. Influence of L-carnitine administration on maximal physical exercise. Eur J Appl Physiol. 1990;61:486-90.

    12. Marconi C, Saassi G, Carpinelli A, Cerretelli P. Effects of L-carnitine loading on the aerobic and anaerobic performance of endurance athletes. Eur J Appl Physiol. 1985; 54:131-5.

    13. Lee JK, Lee JS, Park H, et al. Effect of L-carnitine supplementation and aerobic training on FABPc content and beta-HAD activity in human skeletal muscle. Eur J Appl Physiol. 2007 Jan;99(2):193-9. Epub 2006 Nov 7.

    14.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 Aug;86(8):3579-94.


    15. Benvenga S, Amato A, Calvani M, Trimarchi F. Effects of carnitine on thyroid hormone action. Ann NY Acad Sci. 2004 Nov;1033:158-67

    16. Elisaf M, Bairaaktari E, Katopodis K, et al. Effect of L-carnitine supplementation on lipid parameters in hemodialysis patients. Am J Nephrol. 1998;18:416-421.

    17.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 Sterl. 2004; 81:1578-84.

  • 18. Malaguarnera M, Vacante M, Motta M, Malaguarnera M, Li Volti G, Galvano F. Effect of L-carnitine on the size of low-density lipoprotein particles in type 2 diabetes mellitus patients treated with simvastatin. Metabolism. 2009 Nov;58(11):1618-23. Epub 2009 Jul 15.

  • Evidence Based Rating Scale  

    The Evidence Based Rating Scale is a tool that helps consumers translate the findings of medical research studies with what our clinical advisors have found to be efficacious in their personal practice. This tool is meant to simplify which supplements and therapies demonstrate promise in the treatment of certain conditions. This scale does not take into account any possible interactions with any medication/ condition/ or therapy which you may be currently undertaking. It is therefore advisable to ask your doctor before starting any new treatment regimen.

  • Condition

    Rating

    Explanation

     

     

      

     

     

    AIDS/HIV

     

     

     

     

     

     

     

    Preliminary evidence indicates efficacy. More research is needed to confirm these findings.

     

     

     

     

    Alzheimer’s disease

     

     

     

     

     

    Date Published: 04/18/2005

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