Iron supplements reduce erythrocyte copper-zinc superoxide dismutase activity in term, breastfed infants

Aim: To investigate whether iron supplements compromise copper status in infants. Methods: 214 healthy, term, breastfed Swedish and Honduran infants were randomized to (1) iron supplements (1 mg/kg/d) from 4-9 mo of age, (2) iron supplements from 6-9 mo, or (3) placebo. Blood samples were obtained at 4, 6, and 9 mo and analyzed for plasma copper (p-Cu) and, at 9 mo, for copper/zinc-dependent superoxide dismutase (CuZn-SOD) activity. Results: P-Cu increased with infant age. At 9 mo, Honduran infants had significantly higher p-Cu (1.40±0.29 vs 1.09±0.22 mg/l, p Conclusion: There is a physiologic increase in p-Cu during the first 9 mo of life. Differences in copper status between Swedish and Honduran infants may be due to genetic or nutritional differences. Iron supplementation decreases CuZn-SOD activity, probably due to a negative effect on copper status. Possible clinical implications remain to be elucidated.