Lacteal zinc and copper in relation to volume, total ash and energy during the first three months of lactation of Brazilian women.

The concentrations of zinc and copper were longitudinally studied during the first three months of self-determined lactation periods of nine Brazilian women. Both elements were studied in relation to volume, energy and total ash of milk. During the six bi-weekly intervals, zinc showed a significant difference between the high initial value (as mass/volume), mass/g of ash and mass/kcal) and later values toward the end of the third month, but no significant difference was observed for copper. With respect to all three of those parameters, regression analysis of zinc against length of lactation (six bi-weekly intervals) showed a significant and inverse correlation. Only when expressed as mass/g of ash was copper significantly and directly correlated with length of lactation. The data indicate that zinc secretion into human milk occurs independently of copper and mineral mass and also follows a previously identified physiological pattern.