The effects of the dietary intakes of copper, iron, manganese, and zinc on the trace element content of human milk.

Fifteeen breast-feeding mothers who volunteered for a study of trace elements in human milk, kept two 7-day food records during the course of lactation. The 1st survey week ranged from 6 to 8 weeks and the 2nd survey week from 17 to 22 weeks postpartum. The milk samples submitted for analysis represented a sample of every feed during a period of 24 hr and contained foremilk and hindmilk in equal proportions. The 7-day food records were handled by a computing system to give an average daily food consumption and nutrient intake, but iron was the only trace element given by the system. In order to estimate the trace element intakes of the mothers, mixtures were prepared to represent the average daily food consumption. The trace element concentrations of the mixtures and milk samples were analyzed using the atomic absorption spectrophotometric method. The estimated average daily copper intake was 1.8 mg, the iron intake 16 mg, the manganese intake 5 mg, and the zinc intake 13 mg. The mean copper, iron, manganese, and zinc concentrations of the milk samples were 0.36 +/- 0.07 mg/liter, 0.40 +/- 0.10 mg/liter, 4.5 +/- 1.8 microgram/liter, and 1.89 +/- 0.74 mg/liter for the 1st survey week and 0.21 +/- 0.07 mg/liter, 0.29 +/- 0.09 mg/liter, 4.0 +/- 1.5 microgram/liter, and 0.72 +/- 0.44 mg/liter for the 2nd survey week. A significant positive correlation (P less than 0.01) was observed in the 2nd survey week between maternal manganese intake and the manganese content of human milk. The intake of copper, iron, and zinc, at the present level of intake, did not seem to affect the corresponding trace element levels in human milk.