Plasma zinc and copper levels of infants fed different milk formulas.

The plasma zinc and copper levels of 32 full-term healthy infants, aged 3-4 months, using different infant formulas, were measured. The plasma zinc levels of infants using soy formula (45.1 +/- 19.1 micrograms/dl) and iron-fortified cow's milk formula (61.6 +/- 12.9 micrograms/dl) were significantly lower than those of the infants using cow's milk formula not fortified with iron (77.5 +/- 13.4 micrograms/dl). The plasma copper levels of the infants using the different formulas were not significantly different from each other. Fortification of infant formulas with high levels of iron may reduce the zinc absorption from such formulas.