Results of a new study suggest that giving extra iron to infants who don’t need it, might cause developmental delays. These findings fuel the debate over how much iron infants need and could have huge implications for the baby formula and food industry.

The findings were reported 12 May 2008 at the Joint Meeting of the Pediatric Academic Societies and Asian Society for Pediatric Research in Honolulu, Hawaii. Researchers from the University of Michigan, Ann Arbor found that healthy, well-nourished children fed iron-fortified formula as infants scored an average of 11 points lower on IQ tests and 12 points lower in visual-motor integration at 10 years of age than similar children fed low-iron formula.

A total of 494 healthy Chilean infants who were not iron-deficient at 6 months of age participated in the study. The infants were randomly assigned to 1 of 2 groups—group 1 received an iron-fortified formula containing 12 mg/L ferrous sulfate and group 2 received a low-iron formula containing 2-3mg/L of ferrous sulfate. The long-held theory behind giving supplemental iron is prevention of iron-deficiency.

Principal investigator, Betsy Lozoff, MD, professor of pediatrics and communicable diseases at the University of Michigan, Ann Arbor reported that at the 10-year follow-up, there were no background differences in the two groups, but there were marked differences in neurobehavioral growth and development.

“Our results for 25 years of research show problems with lack of iron. I thought that behavior and development would be better with the 12 mg/L formula. For us to find this result is a big deal. It’s really unexpected,” said Lozoff.

The low-iron group had higher scores on every outcome at 10 years of age. The findings were significant for spatial memory and visual motor integration, and suggestive for IQ, visual perception, and motor coordination compared to children in the iron-fortified group who scored lower on all measures.

Most children who received the 12 mg/L formula did not show lower scores. But the 5 percent of the sample with the highest hemoglobin levels at 6 months showed the poorest outcome.

The randomized design, coupled with the large sample size, suggests a causal relationship between iron-fortified formula and poorer developmental outcomes at 10 years of age. The results raise the possibility that long-term development is adversely affected in iron-sufficient infants who receive formula fortified with iron at the level commonly used in the US. Europe generally uses a lower amount of iron in its formulas.

The next step is to test the participants again when they are 16 years of age; something that has never been done before.

So what’s a parent to do? Given that the American Academy of Pediatrics (AAP) recommends exclusive breastfeeding for the first 6 months and continued breastfeeding for at least a year, the best advice is to breastfeed your baby!

Breastmilk is thought to contain all the nutrients (including iron) a baby needs for the first 6 months of life. Once a baby shows that he/she is ready for solid foods, the best source of iron is meats, followed by iron-fortified cereals. Iron levels are typically not measured until infants are 9 to 12 months of age. Lozoff cautions that it would be premature to suggest a change in practice based on the results of a single study, but urges concerned parents to talk to their baby’s health care provider.