Could Iron-Fortified Formula Be Bad for Development?

Most infant formula in the U.S. is fortified with iron (about 12 mg/L), and keeping infants iron replete is thought to be key to normal development. To examine long-term developmental effects of iron-fortified formula, researchers assessed measures of IQ, math skills, spatial memory, and visual and motor functioning in 473 10-year-olds in Chile who had participated in an anemia prevention trial as infants. Each child had been randomized to receive either iron-fortified formula (mean, 12.7 mg/L) or low-iron formula (2.3 mg/L) between ages 6 and 12 months. Infants with iron deficiency anemia were excluded. At age 12 months, iron deficiency without anemia was significantly more common in the low-iron group than the iron-fortified group (35% vs. 17%); at age 10 years, iron status did not differ between groups.

All developmental test scores were higher in the low-iron group than in the iron-fortified group, but scores were significantly higher only for spatial memory and visual-motor integration (mean differences, 4.6 and 2.6 points, respectively, on 100-point scales). Among a small subset of 26 children with high hemoglobin levels (>12.8 g/dL) at age 6 months, the low-iron group scored significantly better than the iron-fortified group on all tests but one, with mean differences ranging between 11 and 19 points.