CHANGES IN THE FATTY-ACID COMPOSITION OF PRETERM AND TERM HUMAN-MILK FROM 1 WEEK TO 6 MONTHS OF LACTATION

Using capillary gas chromatography, we analyzed the fatty acid composi tion of human milk from 23 women who had delivered prematurely and 16 women who had delivered at term. Milk samples were obtained at 1, 2, 4 , 12, and 26 weeks after delivery. The relative amounts of saturated a nd monounsaturated fatty acids in preterm and term milk remained stabl e throughout the 6 months of lactation. The proportions of linoleate ( 18:2n-6) and a-linolenate (18:3n-3) were similar in preterm and term m ilk and showed an increasing trend from transitional (8.7-9.9% and 0.9 -1.1% of total fatty acids, respectively) to mature milk (9.9-11.8% an d 1.2-1.5%, respectively). The proportions of the major long-chain pol yunsaturated fatty acids (LCP), 20:3n-6, 20:4n-6, 22:5n-3 and 22:6n-3, were highest at 1 week and decreased thereafter in both types of milk . In term milk, the proportion of LCP continued to decrease from 1 mon th to 6 months, whereas in preterm milk it was fairly constant. Conseq uently, at 6 months of lactation, the relative content of arachidonate (20:4n-6) was 1.5 times (p < 0.05) and that of docosahexaenoate (22:6 n-3) was two times higher (p < 0.01) in preterm than in term milk. We conclude that in long-term lactation, preterm human milk provides a si gnificantly higher relative supply of LCP than term human milk. This h igher LCP content may be of special benefit to the development of a pr eterm infant.