ESSENTIAL FATTY ACIDS IN LOW BIRTHWEIGHT INFANTS: EFFECT OF PARENTERAL NUTRITION, FORMULA OR BREAST MILK

Abstract

Long chain polyunsaturated fatty acids 20:4 n-6, 22:4 n-6 and 22:6 n-3 (LCP) are crucial components of all cell membranes, particularly in CNS. Lower n-3 LCP in red cell lipids of infants, and CNS lipids of piglets, fed formula rather than breast milk have been reported. Whether this is due to inadequate 18:3 n-3 in formula fats, or reflects a need for dietary n-3 LCP in the newborn, is controversial. Therefore, the effect of feeding (LBW) infants exclusively formula containing 2% fat as 18:3 n-3 or mother's expressed breast milk for 28d (mean postnatal age 42d) was studied. LBW infants commonly require parenteral nutrition until full enteral feeds can be established. Thus, the effect of time (0-33 days) to establish full feeds (120 mL/kg/day) on LCP status was also determined (n=52 LBW infants). Red cell phosphatidyl-choline, - ethanolamine and plasma phospholipids were purified and fatty acids analyzed by GLC. N-6 and n-3 LCP declined with increasing duration of parental nutrition, irrespective of lipid infusion. Once enteral feeds were established, the levels of 20:4, 22:4 and 22:5 n-6, 20:5, 22:5 and 22:6 n-3 and their ratios in all lipids remained equivalent, and were similar among the 3 feeding groups over the next 28 days. It is suggested preterm infant formula should contain at least 1% Kcal as 18:3 n-3, and that this intake provides for similar levels of 22:6 n-3 to infants fed breast milk for over the first 1-2 mths of life. Early parenteral nutrition, however, results in depletion of LCP.