BACKGROUND AND OBJECTIVES:
A wide variation in the composition of breast milk has been reported from various countries. The aim of this study was to evaluate zinc (Zn) and copper (Cu) concentrations in the breast milk of lactating mothers as a function of lactation time and the relationship between these concentrations and the characteristics of mother–infant dyads.
Mother–infant dyads were recruited immediately at the second week postpartum. Inclusion criteria were as follows: (1) gestational age ≥37 weeks; (2) birth weight ≥2500 g; and (3) no chronic illness in the infant or mother. Anthropometric measurements of the mother–infant dyads were taken. Maternal hemoglobin was measured at week 2 and month 4 postpartum. The samples of human milk were collected postpartum at week 2 and months 2, 4, and 9 postpartum. Zn and Cu concentrations were determined by using an atomic absorption spectrophotometer. Data were presented as mean ± SD.
The mean concentrations of Zn and Cu (n = 172) were 4.84 ± 2.24 mg/L and 452 ± 129 μg/L, respectively, at week 2. There was a correlation between Zn and Cu concentrations at week 2. There was a significant reduction (P < .05) in Zn and Cu concentrations at 4 months’ postpartum (n = 108; 4.88 ± 2.40 mg/L and 453 ± 123 μg/L at week 2, 2.42 ± 0.90 mg/L and 298 ± 233 μg/L, respectively, at month 4 of lactation). The mean concentrations of Zn and Cu (n = 69) were 1.43 ± 0.85 mg/L and 556 ± 350 μg/L, respectively, at month 9. No significant relationship was found between concentrations of Zn and Cu in breast milk and evaluated parameters such as gender, weight, height, head circumference of infants and maternal age, height and BMI, parity, and birth interval. The average concentrations of Zn in breast milk at the second month postpartum were significantly higher in mothers with a history of gestational anemia than in those with no anemia (3.60 ±1.22 mg/L and 3.16 ±1.30 mg/L, respectively; P = .043). At the second week postpartum, maternal hemoglobin was negatively correlated with Cu concentrations in breast milk (n = 167, r = –0.119, P = .010). At 4 months’ postpartum, maternal hemoglobin was negatively correlated with Zn concentrations in breast milk (n = 107, r = –0.225, P = .020). The average concentrations of Zn in breast milk at the fourth month postpartum was significantly lower in mothers taking iron supplementation during the postpartum period than in those with no supplementation (1.21 ± 0.65 mg/L and 1.67 ± 0.98 mg/L, respectively; P = .025).
Concentrations of Zn and Cu in breast milk decreased as lactation continued. Maternal anemia and iron supplementation could influence the status of Zn and Cu in breast milk. Further studies are needed to clarify this effect.
- Copyright © 2015 by the American Academy of Pediatrics