Zinc concentrations in human milk and infant serum during the first six months of lactation.
Zinc and copper concentrations in human milk and in serum from exclusively-breast-fed infants born at full-term were serially determined during the first 3 months of life by the atomic absorption spectrophotometric method. Zinc and copper concentrations of human milk decreased as the stage of lactation progressed. The mean value of the concentration of serum zinc at birth was just below the value previously reported for school children, significantly decreased at one month of age (p less than 0.02), then returned to the level at birth at 2 months of age, and reached at 3 months of age to the level of school children. On the other hand, the mean value of serum copper at birth was markedly low, and rapidly increased until 2 months of age and then gradually increased until 3 months of age. These changes in serum zinc and copper concentrations during early infancy suggested that human milk can provide sufficient zinc and copper for full-term infants during the first 3 months of life. Calculated daily zinc and copper intakes in infants fed on human milk were lower than recommended values. It is necessary to reconsider the appropriateness of previously recommended values for breast-fed animals.