A randomized trial of two levels of iron supplementation and developmentaloutcome in low birth weight infants

Objectives: To investigate the effect of increased iron intakes on hematolo gic status and cognition in low birth weight infants. Study design: We randomly assigned 58 infants to receive formula with 13.4 mg iron/L (normal iron) or 20.7 mg iron/L (high iron). At baseline, dischar ge, and at 3, 6, 9, and 12 months' corrected age, we assessed anthropometry ; infections; red blood cell hemoglobin, catalase, glutathione peroxidase, red blood cell fragility (hydrogen peroxide test), and superoxide dismutase values; plasma malondialdehyde, ferritin, iron, transferrin, zinc and copp er levels; and diet intake. Griffiths' Development Assessment was done at 3 , 6, 9, and 12 months only. Results: No statistical differences (P <.05) were noted for weight, catalas e or malondialdehyde levels, red blood cell fragility, or Griffith's Develo pment Assessment. Iron intakes were greater in the high iron group except a t 12 months. Hemoglobin (high iron, 123 +/- 9; normal iron, 118 +/- 8) was not different at 3 months (P =.07). Plasma zinc levels (high iron, 70 +/- 1 4; normal iron, 89 +/- 27) and copper levels (high iron, 115 +/- 26; normal iron, 132 +/- 27; P =.06) at 12 months suggested inhibition of absorption by high iron formula. Glutathione peroxidase levels were higher in the high iron group. The total number of respiratory tract infections was greater i n the high iron group (3.3 +/- 0.9) than in the normal iron group (2.5 +/- 0.9). Conclusion: In terms of cognitive outcome, there is no advantage associated with elevated iron intake for low birth weight infants.