160 Fatty Acid Composition of Human Milk in a Portuguese Urban Population:Prospective Study from 7 Days to 16 Weeks of Lactation

Abstract

Fat in human milk varies during a feed, during the day and throughout the period of lactation. Fatty acid (FA) composition varies over the course of the day and during lactation. Aim: To evaluate FA composition in human milk, from 7 days (transitional milk) to 16 weeks of lactation (mature milk) and to assess the composition stability of these FA throughout this period. Methods: Mothers living in urban area of Porto who accepted to participate in the study were selected according to inclusion criteria (healthy term newborn exclusively breast-feeding). Pooled human milk was collected from all feedings over 24 hours at the following times: 7 days and 4, 8, 12 and 16 weeks of lactation. FA were analysed through capillary gas chromatography. Comparisons were made (Oneway ANOVA). Correlations between FA were made through Pearson and Spearman correlation coefficient. Results: 31 mothers completed the follow-up period. Total saturated fatty acids (SFA) progressively increased from 40.50 ± 3.72 (% wt/wt) at 7th day up to 43.08 ± 4.61 at the 16th week of lactation, whereas total monounsaturated fatty acid decreased from 33.04 ± 2.58 (% wt/wt) to 31.48 ± 3.32, in the same period. Arachidonic acid (AA) markedly decreases with the stage of lactation. Docosahexaenoic acid (DHA) content decreases lightly from the 7th day to the 4th week of lactation, remaining stable throughout the rest of the lactation period. No significant correlation was found between the levels of linonleic and a-linolenic acid, and their long-chain metabolites AA and DHA. Conclusions: Despite fluctuations in the contents of AA and DHA, the ratio AA/DHA did not significantly change throughout the period of lactation. The ratio AA/DHA remained constant during the study, suggesting a protective mechanism, as AA and DHA are essential structural components of all tissues and particularly of retina and neuronal tissues.