Iron, zinc, copper, and manganese in infant formulas.

The concentrations of the trace elements iron, zinc, copper, and manganese were determined in 53 regular infant formulas and 41 special infant formulas used for clinical disorders. Several infant formulas had lower concentrations of trace elements than human milk. The ranges of concentrations found in the formulas were as follows: Iron, 0.0 to 57.5 mg/L; copper, 0.01 to 2.14 mg/L; zinc, 0.10 to 13.5 mg/L; and manganese, 0.0 to 7.8 mg/L. In addition to the wide variation in absolute amounts of the trace elements in the formulas, large variations in the ratios of trace elements were found. While the average ratios of zinc/copper, zinc/iron, and iron/manganese in human milk range from 3.3 to 10, 2.5 to 10, and 25 to 100, respectively, they ranged from 0.4 to 74, 0.02 to 40, and 0.04 to 425 in the formulas. These differences in the ratios may be important, as the ratio can affect the absorption of the individual elements. These findings indicate that more attention should be given to the trace element levels in infant formulas.