Clinical safety of iron-fortified formulas

Background. Iron-fortified formulas are recommended throughout infancy and are frequently used beyond, yet safety aspects have been inadequately studi ed. Iron could theoretically increase pro-oxidant stress, with potential ad verse effects, including infection risk, and some clinicians suspect that i ron-fortified formulas induce gastrointestinal disturbance. Objective. A planned component of a large intervention trial has been to te st the hypothesis that infants receiving iron-fortified formula do not have a higher incidence of infections (primary outcome) or gastrointestinal pro blems (secondary outcome) than infants on low iron-formulas or cow's milk. Methods. Children (n = 493) 9 months old receiving cow's milk were recruite d in 3 UK centers and randomized to: 1) cow's milk as before, 2) formula co ntaining .9 mg/L of iron, or 3) an otherwise identical formula but containi ng 12 mg/L of iron. Children were followed at 3 monthly intervals and the e pisodes of infections, diarrhea and constipation, and general morbidity to 18 months old were recorded. Hematologic indices of iron status were determ ined at 18 months old. Results. Serum ferritin concentrations were increased in infants receiving iron-fortified formula but there were no intergroup differences in incidenc e of infection, gastrointestinal problems, or in general morbidity or weigh t gain. Conclusions. We were unable to identify adverse health effects in older inf ants and toddlers consuming a high iron-containing formula (12 mg/L) even w hen used in populations with a low incidence of iron deficiency.