Supplements

Carnitine

Carnitine, in the form of L-carnitine, is a trimethylated amino acid that is essential for the transformation of fatty acids into energy for muscular activity. This transformation occurs in the mitochondria, producing coenzyme A.

Carnitine is not used for protein synthesis or as a neurotransmitter like other amino acids. Its main function in the body is to help transport long-chain fatty acids, which are burned within the cells. This is a major source of energy for the muscles.

Using carnitine will give an energy boost, which, in addition to converting body fat to fuel, will elevate certain enzymes needed to metabolize sugars, starches, and other carbohydrates. Athletes and casual exercisers can benefit from carnitine supplementation because it reduces the accumulation of lactic acid, which is responsible for the "burn" felt inside the muscles during and after workouts. This may enable exercisers to "gain" without the "pain", as one study confirmed.

Carnitine also clears the bloodstream of ammonia and aids in creating glycogen, the form in which the body stores glucose.

Carnitine is a key nutrient for helping to prevent muscle atrophy. Anyone suffering from a severe degenerative disease, such as cancer or AIDS, stands to gain from carnitine supplementation.

Taking 2 grams of carnitine per day for four weeks, hospital-based studies show, can cut the number of complications from heart attack (including chest pains [angina], heart rhythm disturbances, and heart failure) in half.

Without carnitine, cardiomyopathy, a disease of the heart muscle, becomes a distinct possibility. This amino acid protects the heart from damage when a heart attack or a spasm cuts off the oxygen supply.

Congestive heart failure flaws our ability to make carnitine. However, taking 900 mg per day improved the health of one group of congestive heart failure patients, significantly increasing both their energy and their ability to exercise.

Carnitine is considered indispensable for infants. Babies usually get carnitine through breast milk or fortified formulas. Breast feeding mothers who are vegetarians need to take carnitine supplements.

Low thyroid function indicates a need for carnitine to help overcome low energy levels and the tendency to gain weight.

Kidney dialysis rinses away amino acids, causing a weak, tired condition, which is threatened by high triglycerides.

Carnitine may be of some value in treating diabetes, studies suggest, hypertension, liver disease, and immune problems.

Deficiency: Deficiency or depletion can occur secondary to various genetic and acquired disorders and conditions that impair the efficiency of carnitine reabsorption or increase the rate of excretion. Primary carnitine deficiency usually results from genetic disorders in carnitine transport. Such deficiency usually presents before age 5, and may be manifested by progressive cardiomyopathy, skeletal muscle weakness, and episodes of fasting hypoglycemia.

Dietary deficiencies are rare, but occur most often in vegetarians, preterm infants, and during pregnancy or lactation. However, as vegetarians often have low-fat diets, they often have less risk of cardiovascular disease. Deficiencies may increase symptoms of fatigue, angina, muscle weakness, or confusion.

Sources: The primary dietary sources of L-carnitine are red meats. Secondary sources include other animal-based food products such as fish, poultry, and milk products. Lesser sources include tempeh (fermented soybeans), wheat, and avocados.

Precautions: For supplementation, the L-carnitine form, alone or bound either to acetic or propionic acid, should be used. The D-carnitine form has produced undesirable side effects and should not be used.

Supplements in large quantities (approximately 5 g/day by an adult) may cause diarrhea or fish odor syndrome.

• Not recommended for individuals with active liver or kidney disease.
• Supplementation for improvement of fat metabolism and muscular performance should probably be stopped one week each month.
• Additional research into long-term safety as a supplement is needed.

Dosage Ranges and Duration of Administration: Carnitine is available in several commercial preparations.

The L-carnitine form is most often recommended. It is available alone, or linked with acetic acid or propionic acid.

L-carnitine (LC) is the most widely available form, is least expensive, and has been studied the most.

L-acetylcarnitine (LAC) appears to be best for Alzheimer's disease and brain defects.

• To improve fat metabolism and muscular performance, supplementation levels of 1,000 to 2,000 mg per day, usually divided into two doses
• or treatment of ischemic heart disease and hyperlipid states (specifically, Type IV hyperlipidemia): doses of 600 to 1,200 mg tid or 750 mg bid
• For treatment of alcoholic fatty liver: 300 mg tid
• For treatment of male infertility: 300 to 1,000 mg tid

INTERACTIONS

Azidothymidine (AZT); Zidovudine
In an in vitro study with human muscle tissue, the addition of L-carnitine (5 mM) to muscle cultures pretreated with AZT (0.0027 to 135 mcg/mL) preserved the integrity and volume of mitochondria (Semino-Mora et al. 1994). Coadministration of L-carnitine to AIDS patients on AZT therapy may prevent the development of myotoxicity typically associated with this drug.

Doxorubicin
In one study, isolated cardiac myocytes and rat mitochondria perfused with doxorubicin (5 mM) treatment with L-carnitine reversed the cardiotoxic affects associated with the drug without affecting therapeutic effects (Sayed-Ahmed et al. 1999). In another study with mice, carnitine significantly decreased cardiac toxicity at both acute high and chronic intermittent low doses (Alberts et al. 1978). The cardiotoxic effects of doxorubicin were not observed in children treated with a combination of doxorubicin (30 to 60 mg/kg) and carnitine (1 to 2 g) (Chavez et al. 1997).