A study of factors that may influence the determination of copper, iron, and zinc in human milk during sampling and in sample individuals

The aim of this study was to establish the possible effects of the sampling protocol (between-breast, within-feed, and diurnal differences) and the mo ther's personal factors (age, parity, iron supplementation, smoking habits, and lactation period) on the copper, iron, and zinc contents in human milk . One hundred thirty-six human milk samples identified by their origin and sa mpling conditions were analyzed. The samples were obtained from the 2nd to 15th d postpartum from 62 women. The data on the individuals required for t he study were available. Mineral determinations were analyzed by flame atom ic absorption spectrometry following a standarized protocol. The results showed that iron contents were higher in hind-milk samples and at the nighttime feeding and depended on the breast from which the sample w as taken. The copper and zinc concentrations showed no significant variatio ns. There was no significant relationship among the mothers' age, parity, s moking habits, iron supplementation, and copper content. Milk from older wo men had lower zinc contents than that of younger women. Increased amounts o f iron were found in multiparous women. Between colostrum and transitional milk, a sharp decrease in zinc content was observed, whereas copper and iro n contents remained constant. All of these results make it clear that standardized sampling protocols are needed in order to obtain comparable values.