Articles

L-Carnitine

Introduction

L-carnitine is an amino acid that is made in the human body. For this reason, L-carnitine is usually not considered to be an essential nutrient. However, premature infants and some adults cannot make L-carnitine in sufficient amounts, which necessitates supplementation.

L-carnitine is only found in animal food sources such as meat, poultry, and dairy products. Human breast milk is an important source of L-carnitine for infants.

Dosage Info

Dosage Range

500 milligrams to 4 grams daily.

Most Common Dosage

250mg, 2 times a day.

Dosage Forms

Tablets, capsules, and powder.

Interactions and Depletions

Depletions

Reported Uses

Studies suggest that L-carnitine may have a number of applications in supporting the overall health of the heart and treating heart-related disorders. L-carnitine has shown promise in patients with irregular heartbeat, heart muscle inflammation (cardiomyopathy) and angina. (1) , (2) , (3)

Studies have also looked at the use of large doses of L-carnitine to improve immune response in AIDS patients. (4) Other research suggests that L-carnitine can lower "bad," or LDL, cholesterol levels while raising HDL levels, the so-called "good" cholesterol. (5) Scientists think these cholesterol-lowering benefits may carry over into the treatment of alcoholic liver disease. (6) , (7)

Lab and animal studies have been published that indicate L -carnitine reduces the activity thyroid hormone in some tissues. These findings prompted Benvenga and colleagues to evaluate whether L-carntine would benefit patients with hyperthyroidism. The study, which lasted six months, compared L-carntine to placebo in 50 women with hyperthyroidism. The trial concluded that 2 or 4 grams of L-carnitine per day is effective in preventing and reducing the nine hyperthyroid related symptoms evaluated and has a beneficial effect on bone mineral density based on several other factors evaluated. (8)

Additionally, treatment with L-carnitine may support health in people with diabetes. (9) It may also enhance walking ability to those suffering from peripheral vascular disease, a painful circulatory disease that affects the lower extremities. (10) L-carnitine may support health in people undergoing regular kidney dialysis. (11) , (12) , (13) It may also increase fertility in males by boosting sperm counts and making the sperm more mobile. (14) , (15) , (16)

Toxicities & Precautions

Introduction

[span class=alert]Be sure to tell your pharmacist, doctor, or other health care providers about any dietary supplements you are taking. There may be a potential for interactions or side effects.[/span]

General

This dietary supplement is considered safe when used in accordance with proper dosing guidelines.

However, the use of D-carnitine should be avoided. It competes with L-carnitine and can decrease the L-carnitine in the heart and skeletal muscles, which can result in muscle pain, decreased exercise tolerance, and loss of muscle function.

Health Conditions

Studies show that this dietary supplement has the ability to decrease the activity of thyroid hormone. If you have any type of thyroid disease talk to your doctor or health care professional before taking this dietary supplement. (17)

Pregnancy / Breast Feeding

To date, the medical literature has not reported any adverse effects related to fetal development during pregnancy or to infants who are breast-fed. Yet little is known about the use of this dietary supplement while pregnant or breast-feeding. Therefore, it is recommended that you inform your healthcare practitioner of any dietary supplements you are using while pregnant or breast-feeding.

Age Limitations

To date, the medical literature has not reported any adverse effects specifically related to the use of this dietary supplement in children. Since young children may have undiagnosed allergies or medical conditions, this dietary supplement should not be used in children under 10 years of age unless recommended by a physician.

References

  1. View Abstract: 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. Oct1985;23(10):569-72.
  2. View Abstract: Mondillo S, et al. Therapy of Arrhythmia Induced by Myocardial iIschemia. Association of L-carnitine, Propafenone and Mexiletine. Clin Ter. Dec1995;146(12):769-74.
  3. View Abstract: Winter S, et al. The Role of L-carnitine in Pediatric Cardiomyopathy. J Child Neurol. Nov1995;10(Suppl2):S45-51.
  4. View Abstract: De Simone C, et al. High Dose L-carnitine Improves Immunologic and Metabolic Parameters in AIDS Patients. Immunopharmacol Immunotoxicol. Jan1993;15(1):1-12.
  5. Pola P, et al. Statistical Evaluation of Long-term L-carnitine Therapy in Hyperlipoproteinemias. Drugs Exptl Clin Res. 1983;9:925-34.
  6. View Abstract: Sachan DS, et al. Ameliorating Effects of Carnitine and Its Precursors on Alcohol-induced Fatty Liver. Am J Clin Nutr. May1984;39(5):738-44.
  7. View Abstract: Lapinski TW, Grzeszczuk A. The impact of carnitine on serum ammonia concentration and lipid metabolism in patients with alcoholic liver cirrhosis. Pol Merkuriusz Lek. Jul2003;15(85):38-41.
  8. View Abstract: 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. Aug2001;86(8):3579-94.
  9. View Abstract: Mingrone G, et al. L-carnitine Improves Glucose Disposal in Type 2 Diabetic Patients. J Am Coll Nutr. Feb1999;18(1):77-82.
  10. View Abstract: Brevetti G, 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. Feb1992;13(2):251-55.
  11. View Abstract: Elisaf M, et al. Effect of L-carnitine Supplementation on Lipid Parameters in Hemodialysis Patients. Am J Nephrol. 1998;18(5):416-21.
  12. View Abstract: Bellinghieri G. Carnitine and hemodialysis. Am J Kidney Dis. Mar2003;41(3 Suppl 1):S116-22.
  13. View Abstract: Vazelov E. L-carnitine consecutively administered to patients on hemodialysis improves beta-cell response. Int J Artif Organs. Apr2003;26(4):304-7.
  14. View Abstract: Vitali G, et al. Carnitine Supplementation in Human Idiopathic Asthenospermia: Clinical Results. Drugs Exp Clin Res. 1995;21(4):157-59.
  15. View Abstract: Lenzi A. Use of carnitine therapy in selected cases of male factor infertility: a double-blind crossover trial. Fertil Steril. Feb2003;79(2):292-300.
  16. View Abstract: 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. Jun2004;81(6):1578-84.
  17. View Abstract: 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. Aug2001;86(8):3579-94.