Zinc concentrations in human milk and infant serum during the first six months of lactation

Normal supply of zinc to the newborn via milk is essential for normal development. Using ICP-OES, we analyzed changes in the level of Zn in milk and infant serum in the neonatal period (Day 1 and Day 28 post partum) and at 6 months after delivery, in the cohort of 60 mothers and exclusively breastfed babies. Zn level in the serum showed increase (significant at 6 months) during this period (mg/mL): Day 1: 0.52 +/- 0.12; Day 28; 0.59 +/- 0.19; 6 months: 0.68 +/- 0.28. The concentration of Zn in the milk showed an opposite (decreasing) trend during the follow up: Day 1: 4.70 +/- 1.74 mg/L; Day 28: 2.65 +/- 1.06; 6 months: 0.46 +/- 0.36. A significant negative correlation was established between serum and milk [Zn] at day 28 (R = -0.338; p = 0.008), whereas a positive correlation was found at 6 months between these parameters (R = 0.306; p = 0.018). There was no significant correlation between [Zn] in the milk and serum and infants' body mass, mothers' age and mass at delivery. The level of Zn in the milk at 6 months of lactation is not sufficient to meet the recommended values. This implies that in Serbian population, Zn supplementation might be needed in the later phase of lactation