The concentrations of copper and zinc in human milk. A longitudinal study.

Twenty-seven healthy Finnish mothers were followed during the course of their entire lactation period. A total of 229 individual milk samples, collected in the beginning and at the end of each feed during a 24-h period, were obtained from the 2nd week to the 9th month of lactation. The copper and zinc concentrations were determined by atomic absorption spectrophotometry. The concentrations of the trace-elements investigated were dependent on the stage of lactation. The median copper and zinc concentrations decreased during the course of lactation from about 0.60 mg/l and 4.0 mg/l to 0.25 mg/l and 0.5 mg/l, respectively. The importance of considering the stage of lactation in the evaluation of the trace-element nutrition value of breast milk should be emphasized. The calculated means of the concentrations of these trace-elements in mature human milk presented in the literature seem to overestimate the actual levels in prolonged lactation.