The effects of the dietary intakes of copper, iron, manganese, and zinc on the trace element content of human milk1-3

Fifteen 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 tg/hiter, 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 jig/liter, and 0.72 ± 0.44 mg/liter for the 2nd survey week. A significant positive correlation (P < 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. Am. J. C/in. Nut,. 33: 227-231. 1980. The composition of human milk is not constant. Variations of trace element content have been shown to occur from mother to mother and also with the stage of lactation (1-4). In our follow-up study of 27 mothers a decrease in the iron, copper, and zinc concentration of human milk was associated with increasing stage of lactation (5, 6). The manganese concentration was at a minimum between the 4th to 5th month of lactation, whereafter a rising tendency was observed (E. Vuori, unpublished observations). In this context a wide range of individual variation in the trace element concentrations was confirmed. One factor that may influence the trace element content of human milk is the variation in the intake of these elements. The trace element content of the diets of lactating mothers has not been extensively investigated, and correlations of trace elements other than iron (7) between maternal diet and human milk are lacking. Animal experiments (goats, cows, ewes) have shown that if the total intake is sufficient, nutritional factors play only a minor role; the increased intake of manganese and zinc, however, increases the amount of these elements in the milk of cows and ewes (1-4, 8, 9). In order to study the influence of the intake of trace elements on the concentration of the corresponding elements in human milk, the copper, iron, manganese, and zinc concentrations in the individual diets and milk samples of 15 lactating mothers were analyzed twice From the Department of Public Health Science. University of Helsinki, Haartmaninkatu 3, SF-00290 Helsinki 29, The Department of Nutrition, University of Helsinki, Viikki, B-tab, SF-00710 Helsinki 71, and The Children’s Hospital, University of Helsinki, Stenb#{228}ckinkatu 11, SF-00290 Helsinki 29, Finland. 2 Supported by a grant from the Yrjo Jahnsson Foundation, Helsinki, Finland. ‘Address reprint requests to: Dr. E. Vuori, Department of Public Health Science, University of Helsinki, Haartmaninkatu 3, SF-00290 Helsinki 29, Finland. at P E N N S Y LV A N IA S T A T E U N IV P A T E R N O IB R A R Y on F ebuary 1, 2013 ajcn.trition.org D ow nladed fom