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<0.001) and CuZn-SOD activity (1.09+/-0.29 vs 0.93+/-0.21 U/mg Hb, p<0.001) than Swedish infants. Infants receiving iron supplements from 4-9 mo had significantly lower CuZn-SOD at 9 mo of age (0.95+/-0.27 vs 1.08+/-0.24 U/mg Hb, p=0.023) than those receiving placebo.

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.