CHANGES IN HAIR ZINC AND COPPER CONCENTRATIONS OF BREAST FED AND BOTTLE FED INFANTS DURING THE FIRST SIX MONTHS

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Abstract
A longitudinal study of 35 full-term breast-fed (20 males, 15 females; mean birthweight = 3540 g) and 25 full-term bottle-fed infants (14 males, 11 females; mean birthweight = 3466 g) was carried out to compare the effect of method of feeding on hair Zn and Cu concentrations. Hair samples were collected at 30 .+-. 2, 90 .+-. 4 and 180 .+-. 4 days of age and analyzed for Zn and Cu by instrumental neutron activation procedures. Mean daily Zn and Cu intakes were calculated at monthly intervals from 3-day diet records and test weight data for the breast-fed group. Only the male bottle-fed infants showed a significant decline in hair Zn concentration (P < 0.01) during the 6-mo. study. Male infants may have a higher requirement for Zn than females in early infancy. No comparable systematic decline in hair Zn levels was evident in the female bottle-fed infants or the male and female breast-fed infants. The absence of any fall in hair Zn concentrations in the breast-fed infants, despite their significantly lower (P < 0.01) dietary Zn intakes compared to the bottle-fed group, is attributed to the superior bioavailability of Zn from breast milk. Hair Cu levels rose during the first 3 mo. in both groups and subsequently declined between 3 and 6 mo. These changes were not significantly related to sex or method of feeding but were associated with the redistribution of Cu which occurs during early infancy.