Lipid metabolism and therapyEfficiency of conversion of α-linolenic acid to long chain n-3 fatty acids in manBrenna, J. Thomas Author Information Division of Nutritional Sciences, Savage Hall, Cornell University, Ithaca, New York, USA Correspondence to J.T. Brenna, Division of Nutritional Sciences, Savage Hall, Cornell University, Ithaca, NY 14853, USA. Tel: +1 607 255 9182; fax: +1 607 255 1033; e-mail: [email protected] Abbreviations 18:3n-3*: isotopically-labeled 18:3n-3 20:5n-3*: isotopically-labeled 20:5n-3 22:5n-3*: isotopically-labeled 22:5n-3 22:6n-3*: isotopically-labeled 22:6n-3 AUC: area under the curve LCP: long chain polyunsaturates, with 20 or more carbons PUFA: polyunsaturated fatty acids of all chain lengths Current Opinion in Clinical Nutrition and Metabolic Care: March 2002 - Volume 5 - Issue 2 - p 127-132 Buy Abstract α-Linolenic acid (18:3n-3) is the major n-3 (ω3) fatty acid in the human diet. It is derived mainly from terrestrial plant consumption and it has long been thought that its major biochemical role is as the principal precursor for long chain polyunsaturated fatty acids, of which eicosapentaenoic (20:5n-3) and docosahexaenoic acid (22:6n-3) are the most prevalent. For infants, n-3 long chain polyunsaturated fatty acids are required for rapid growth of neural tissue in the perinatal period and a nutritional supply is particularly important for development of premature infants. For adults, n-3 long chain polyunsaturated fatty acid supplementation is implicated in improving a wide range of clinical pathologies involving cardiac, kidney, and neural tissues. Studies generally agree that whole body conversion of 18:3n-3 to 22:6n-3 is below 5% in humans, and depends on the concentration of n-6 fatty acids and long chain polyunsaturated fatty acids in the diet. Complete oxidation of dietary 18:3n-3 to CO2 accounts for about 25% of 18:3n-3 in the first 24 h, reaching 60% by 7 days. Much of the remaining 18:3n-3 serves as a source of acetate for synthesis of saturates and monounsaturates, with very little stored as 18:3n-3. In term and preterm infants, studies show wide variability in the plasma kinetics of 13C n-3 long chain polyunsaturated fatty acids after 13C-18:3n-3 dosing, suggesting wide variability among human infants in the development of biosynthetic capability to convert 18:3n-3 to 22:6n3. Tracer studies show that humans of all ages can perform the conversion of 18:3n-3 to 22:6n3. Further studies are required to establish quantitatively the partitioning of dietary 18:3n-3 among metabolic pathways and the influence of other dietary components and of physiological states on these processes. © 2002 Lippincott Williams & Wilkins, Inc.