Review Physiological aspects of human milk lipids Berthold Koletzko a, , Maria Rodriguez-Palmero a , Hans Demmelmair a , Natas ˇa Fidler a , Robert Jensen b , Thorsten Sauerwald a a Department of Pediatrics, Division of Metabolic Disorders, Molecular Disease and Nutrition, Kinderklinik and Kinderpoliklinik, Dr. von Haunersches Kinderspitel, Ludwig-Maximilians-University of Munich, Lindwurmstr. 4, D-80337 Munich Germany b Department of Nutritional Science, University of Connecticut, Storrs, CT, USA Abstract Human milk from healthy and well-nourished mothers is the preferred form of feeding for all healthy newborn infants. The nutrient supply with human milk supports normal growth and development of the infant. Here the general characteristics of human milk lipids and recent knowledge on lactational physiology, composition and functional aspects of human milk lipids are discussed. Lipids in human milk represent the main source of energy for the breastfed baby and supply essential nutrients such as fat-soluble vitamins and polyunsaturated fatty acids (PUFA). The essential fatty acids linoleic and a-linolenic acids (LA and ALA) are precursors of long-chain polyunsaturated fatty acids (LC-PUFA), including arachidonic (20:4n  6) and docosahexaenoic (22:6n  3) acids (AA and DHA). LC-PUFA serve as indispensable structural components of cellular membranes and are deposited to a considerable extent in the growing brain and the retina during perinatal development. The supply of preformed LC-PUFA with human milk lipids has been related to functional outcomes of the recipient infants such as visual acuity and development of cognitive functions during the first year of life. Recent stable isotope studies indicate that the major portion of milk PUFA is not derived directly from the maternal diet, but stems from endogenous body stores. Thus, not only the woman’s current but also her long-term dietary intake is of marked relevance for milk fat composition. D 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Human milk Arachidonic acid Docosahexaenoic acid Infant nutrition Infant development 0378-3782/01/$ – see front matter D 2001 Elsevier Science Ireland Ltd. All rights reserved. PII:S0378-3782(01)00204-3 Abbreviations: BSSL, bile-salt stimulated lipase; PUFA, polyunsaturated fatty acids; LC-PUFA, long-chain polyunsaturated fatty acids; VEP, visual evoked potentials; LA, linoleic acid (18:2n6); ALA, a-linolenic acid (18:3n3); AA, arachidonic acid (20:4n6); EPA, eicosapentaenoic acid (22:6n3); DHA, docosahexaenoic acid (22:6n3). * Corresponding author. Fax: +49-89-5160-3336. E-mail address: Berthold.Koletzko@kk-i.med.uni-muenchen.de (B. Koletzko). www.elsevier.com/locate/earlhumdev * Early Human Development 65 Suppl. (2001) S3 – S18