Changes in hair zinc and copper concentrations of breast fed and bottle fed infants during the first six months.

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