ABSTRAU. Erythrocyte superoxide dismutase (ESOD) activity reflects copper utilization and the risk of copper deficiency. To investigate the possible effects of inorganic iron on the metabolism of copper in low birth weight infants, we have measured ESOD activities in three groups of infants receiving different iron supplements. Fifty-five low birth weight infants were randomly assigned to receive daily from 28 d either 13.8 mg (HiFe), 7 mg (MidFe), or no elemental iron (NatFe) as iron edetate. At 27 d, 8, 12, and 20 wk postnatal age, infants were weighed and measured and hematologic indices, plasma ferritin, zinc, and copper concentrations, and ESOD activities were assayed. Anthropometrical and hematologic indices and plasma copper and zinc concentrations did not differ among treatment groups at any time, but at 20 wk, plasma ferritin concentrations [(pg/L) mean; SD] were lower in the NatFe group (17; 2.0) than in the HiFe group (32; 1.9: 95% confidence interval for mean difference 6.6 to 22.0, p < 0.01). ESOD activities (U/g Hb) were similar in HiFe (1447; 263), MidFe (1552; 322), and NatFe (1538; 382) groups at 27 d, but by 20 wk activities in the HiFe group (1537; 211) were lower than in the MidFe (1789; 403: 95% confidence interval 38 to 466, p < 0.05) and NatFe (1858; 304: 95% confidence interval 150 to 492,p < 0.01) groups. The lower ESOD activities found in the HiFe group at 20 wk may reflect altered copper metabolism induced by the iron supplement, but the clinical importance of this observation is unknown. (Pediatr Res 29: 297-301,1991) Abbreviations ESOD, erythrocyte superoxide dismutase CI, confidence interval HiFe, high iron intake LBW, low birth weight MidFe, middle iron intake NatFe, natural iron intake SOD, superoxide dismutase RBC, red blood cell Because iron and copper have similar physicochemical properties, interactions can occur between them that can affect adversely the metabolism of copper (1). The practical relevance of this has been shown in mixed fed healthy infants in whom an iron-fortified (10.2 mg/L) formula achieved a lower intestinal absorption and whole body retention of copper than did the

Aggett, P. J., Barclay, S. and Whitley, J. E. (Department of Child Health, University of Aberdeen, Aberdeen, and Scottish Universities' Research and Reactor Centre, East Kilbride, Scotland). Iron for the suckling. Knowledge of the metabolism of iron by young infants is incomplete but combining practical studies based on detecting the onset of iron depletion with isotopic studies of iron economy may improve our understanding of iron metabolism in infants and our strategies for ensuring their iron supply. The iron accumulated by the fetus is enough to delay the risk of iron deficiency until four, and two months of age in term and preterm infants respectively. Breast fed term infants may not need extra iron until they are six months or older; but whereas low iron formulas are adequate for other infants until about four months of age, therafter infants need extra iron which can be provided effectively in iron fortified formulas. Breast fed low birth weight infants need iron supplements from two months of age but those fed specific low birth weight formulas which are iron fortified should not need extra iron.

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