Carnitine has only recently been noted as an important amino acid (the L- form only) essential to our health. It is found in the diet and can also be made by the body, mainly in the liver and kidneys, from lysine with the help of vitamin C, pyridoxine, niacin, iron, and methionine. Among our foods, carnitine is found mainly in the red meats (thus, the name) with some found in fish, poultry, and milk products and less in tempeh (fermented soybeans), wheat, and avocados. Carnitine is stored primarily in the skeletal muscles and heart, where it is needed to transform fatty acids into energy for muscular activity. It is also concentrated in sperm and in the brain. Carnitine is utilized to transport fatty acids into the cell and across the mitochondrial membranes into our cellular energy factories, the mitochondria. It also increases the rate at which the liver oxidizes (uses) fats, an energy-generating process.
POSSIBLE USES OF L-CARNITINE
Ischemic heart disease
Angina pectoris
Cardiac arrhythmias
Elevated cholesterol and/or
triglyceride levels
Low HDL cholesterol
Atherosclerosis
Muscle weakness
Muscle diseases
General fatigue
Overweight
Poor endurance
Immune suppression
Alcohol abuse
Pregnancy
Hypothroidism
Male infertility
L-carnitine is the active form and can be taken as a safe supplement with positive benefits. With carnitine's effect on fatty acids and energy production, especially in the heart and muscles, it is now known as a nutrient that protects us from cardiovascular disease. It has been shown to reduce blood triglycerides and cholesterol levels by increasing fat utilization; at the same time, carnitine can raise the HDL portion of the cholesterol, which reduces cardiovascular disease risk. L-carnitine also helps with weight loss, usually improves our exercise capacities (possibly through the oxidation of amino acids), and may possibly enhance our muscle building and endurance. These latter two aspects may be a result of the weight loss and better exercise. Many athletes have noted improved endurance with L-carnitine supplementation. In some studies, L-carnitine has been shown to improve the symptoms of angina, reducing pain and allowing more activity. It also may lessen the risk of fatty deposits in the liver associated with alcohol abuse.
Deficiencies of carnitine have been noted, more so recently with people avoiding red meats in the diet. These occur most often in vegetarians and during pregnancy or lactation. Vegetarians, though, often have low-fat diets and otherwise reduced cardiovascular disease risk. Deficiencies may increase symptoms of fatigue, angina, muscle weakness, or confusion. More research is needed to clarify and verify these deficiency states, as well as to establish whether the metabolic benefits of L-carnitine are clearly separate from correcting that deficiency.
The dosage of L-carnitine (not D- or DL-carnitine) suggested to improve fat metabolism and muscular performance is 1000–2000 mg. daily, usually divided into two doses. This is basically safe and can be taken over an extended period, although it probably should be stopped for one week each month, until its long-term safety as a supplement is more clearly established. The Physician's Desk Reference has recommended L-carnitine in the treatment of ischemic heart disease and hyperlipid states (specifically, Type IV hyperlipidemia) in a dosage of 600–1200 mg. three times daily.
Carnitine is not recommended in people with active liver or kidney disease or with diabetes. However, it is definitely recommended for persons with heart problems such as ischemia or arrhythmia or with increased cardiovascular risk, such as high blood fats, and for problems with poor endurance, muscle weakness, or obesity. I am excited about the uses of L-carnitine and look forward to more positive research in the future.