Longitudinal zinc balances in breast‐fed and formula‐fed infants

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Abstract
Longitudinal zinc (Zn) balance studies were performed under domestic conditions in term breast‐fed (n= 10), term formula‐fed (n= 5; Zn concentration in the formula: 4 mg/l) and preterm formula‐fed (n= 3) infants during the first 17 weeks of life. Samples of milk, urine and feces were analyzed by atomic absorption spectrometry. The median daily Zn intake in breast‐fed infants decreased from 0.592 (0.457‐0.829) mg Zn/kg body weight to 0.151 (0.095‐0.304) mg Zn/kg body weight in the first 17 weeks of life; comparable values for bottle‐fed term infants were 0.58 (0.511‐0.701) and 0.674 (0.529‐0.731) mg Zn/kg body weight. The median percent retention of Zn intake was 27 (‐60 to 81.4)% in breast‐fed infants and 21.5 (‐42 to 64)% in formula‐fed infants. In view of the urinary and fecal Zn losses measured, a daily intake of 0.3‐0.5 mg Zn/kg body weight is considered to be sufficient to ensure a Zn retention equivalent to breast‐fed infants. This requires a Zn concentration of 2‐3 mg/1 of Zn depending on milk volume intake.