Carnitine
Description
Carnitine is a nonessential amino acid, which means it is manufactured from other amino acids in the liver; it does not have to be obtained directly through the diet.
Carnitine deficiencies have been identified to result in buildup of acid metabolites in tissues and increased levels of blood fat, triglycerides. Carnitine deficiencies also lead to poor energy production in the heart and poor metabolism of fats. Dr. Ewan Cameron has recently suggested carnitine deficiency may also account for muscle wasting, weakness, and poor sense of well-being in cancer patient. Supplementation with lysine and vitamin C may help correct a low carnitine level.
The role of carnitine in fat metabolism is to help transport free fatty acids into the mitochondria of cells where the fats can be used as a source of energy. Carnitine has also been found to be important in the synthesis and function of sperm in the testes. In male animals, carnitine deficiency can result in infertility.
Recommended Dietary Allowances
An RDA has not been established for carnitine because it is a nonessential amino acid.
Food Sources
Carnitine is a nonessential amino acid, which means it is manufactured from other amino acids in the liver; it does not have to be obtained directly through the diet.
Method of Action
Carnitine is synthesized in the body from the essential amino acid lysine. The conversion of lysine to carnitine in all cells of the body is dependent upon adequate vitamin C levels. It has been estimated that about 0.1 percent of dietary lysine is converted to carnitine in the body. Carnitine is not found in a vegetable-based diet; rather, it is only found in animal products. Therefore, vegetarians who may consume a lysine-deprived diet may have insufficient amounts of carnitine. Animals fed a wheat gluten diet low in lysine and carnitine have significantly lower levels of carnitine in their hearts and skeletal muscles.
Recently, medical studies in Japan and Europe have indicated carnitine supplementation can help lower triglycerides in individuals with elevated blood fats. Doses used are between 400 and 2000mg per day of L-carnitine. D,L-carnitine (the synthetic derivative) has also been found useful in lowering triglycerides, but may have a more significant problem with liver toxicity associated with its excessive use.
Preliminary reports indicate carnitine may be useful for extending endurance in athletes who are engaged in long-term exercise. Carnitine has also been used to treat acid buildup in the blood of diabetics (ketoacidosis).
References
Blackburn, G.L., Grant, J.P., Young, V.R., ed. Amino Acids Metabolism and Medical Applications.
Khan-Siddiqui, L. & Bamji, M.S. Plasma Carnitine Levels in Adult Males in India: Effects of High Cereal Low Fat Diet, Fat Supplementation, and Nutritional Status. Am. J. Clin. Nutr., 33:1259-63, 1980.
Munro, H.N. & Crim, M.C. The Proteins and Amino Acids. Modern Nutrition in Health and Disease, eds: R.S. Goodhart & M.E. Shils, 6 ed., Philadelphia: Lea and Febiger, 1980.
Siliprandi, N. & Ramacci, M.T. Carnitine as a 'Drug' Affecting Lipid Metabolism. in Drugs Affecting Lipid Metabolism, eds: R. Fumagalli, D. Kritchevsky, and R. Paoletti, New York: Elsevier Publishing Co., 1980.
White, A., Handler, P., Smith, E.L., Hill, R.L., & Lehman, I.R., Principles of Biochemistry, 6th ed., New York: McGraw-Hill, 1978.
Young, V.R., Meguid, M., Meredith, D.E., & Bier, D.M. Recent Developments in Knowledge of Human Amino Acid Requirements. Nitrogen Metabolism in Man, eds: J.C. Waterlow & J.M.L. Stephen, London: Applied Science Pubs, 1981.
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