The babies in the study who were not fed iron-fortified formula were fed regular formula. Given the importance of breastfeeding for healthy cognitive development, it is expected that the demonstrated differences in outcomes would have been even greater had the iron-fortified group been compared with breastfed children.

While iron-fortified formula was said to have some benefits for iron-deficient babies, those with sufficient iron levels appeared to be adversely affected. Iron deficiency is not considered a problem for most infants in the industrialized world. Breast milk has been shown to provide infants with sufficient amounts of iron even when mothers are undernourished.

"Most of us in the iron field would be comfortable with formulas having less iron in them," says Dr. Michael Georgieff, Professor of Pediatrics and Child Psychology and Director of the Division of Neonatology and the Institute of Child Developmentat the University of Minnesota. "There may be potential toxicity in certain groups consuming a high-iron formula."

Many formula labels carry messages like "iron fortified" or "infant formula with iron." These messages appeal to parents who have long been told children benefit from receiving iron. In light of this new study, such marketing tactics appear highly irresponsible. In a press statement, INFACT Canada says, "Clearly, formula companies have never taken the time to investigate the potential impact of high-iron formulas on healthy children, and have been marketing iron-fortified products to the general public for years with no warning of its consequences. Unless formula companies change their marketing in light of this evidence, they will be knowingly endangering the cognitive development of the infants who consume their products.