Objective: To determine the efficacy of iron-fortified infant formula in preventing developmental delays and abnormal behavior.
Design: Double-blind, randomized, controlled trial.
Setting: Urban hospital clinic.
Participants: A total of 283 healthy, bottle-fed infants from very low income families. Children with prematurity, low birth weight, and major anomalies and those who had received more than 2 weeks of evaporated-milk feedings were excluded. The groups were similar for sociodemographic background variables. Fifty-eight infants (20.5%) dropped out before any outcome data were gathered; 225, 204, 186, and 154 remained at 6-, 9-, 12-, and 15-month assessments, respectively.
Intervention: Iron-fortified formula (12.8 mg iron per liter) versus regular formula (1.1 mg iron per liter).
Main outcome measures: Iron status was measured on venous blood by determination of hemoglobin, serum iron and iron-binding capacity, serum ferritin, and free erythrocyte protoporphyrin values. The Bayley Scales of Infant Development (mental and psychomotor indexes) and two factors of the Infant Behavior Record (test affect and task orientation) were the outcomes of interest.
Results: All measures of iron status were significantly different between groups (p < 0.001). Psychomotor development patterns differed between groups (F3,520, 3.4; p = 0.02) with time. Mean values were similar at 6 months but differed at 9 and 12 months of age (p < 0.001), with a decline of 6.4 points in the regular-formula group. By 15 months of age the differences were no longer significant (p = 0.23). Mental development and behavior were not affected.
Conclusions: Iron-fortified formula significantly reduced iron deficiency in a high-risk group of infants and prevented a decline in psychomotor development quotients. This effect may be transient, and its long-term significance needs further study.