Gahagan S, et al. - Via enlisting infants from community clinics in low- to middle-income neighborhoods in Santiago, Chile, researchers evaluated variations in cognitive results among adolescents who had earlier been randomly allocated to iron-fortified (12 mg/L) formula or low-iron (2.3 mg/L) formula as part of an iron deficiency anemia prevention trial. Term, singleton infants; birth weight of ≥3.0 kg; and no major congenital anomalies, perinatal complications, phototherapy, hospitalization >5 days, chronic illness, or iron deficiency anemia at 6 months were criteria for inclusion. At the age of 16, cognitive ability, visual perceptual ability, visual memory, and math, vocabulary and comprehension achievement were evaluated using standardized measurements. For visual memory, arithmetic achievement, and reading comprehension achievement, those randomized to iron-fortified formula had lower scores than those randomized to low-iron formula. Compared to adolescents who received a low-iron formula, those who received iron-fortified formula as infants from 6 to 12 months of age at levels recommended in the US had poorer cognitive results. It is essential for brain development to prevent iron deficiency anemia in infancy. The optimal iron supplementation level in infancy, however, is unclear.