Iron-sufficient infants, who were fed iron-fortified formula scored lower on IQ tests than their peers, who were given a low-iron formula.

The study was conducted on Chilean infants who were not anemic, but were still given iron fortified formula to prevent iron deficiency. They were randomly arranged into two groups, receiving either iron-fortified formula (12 mg/L ferrous sulfate) or low-iron formula (2.3 mg/L ferrous sulfate) for a year, from 6 months of age.

Hemoglobin (oxygen carrier protein in red blood cells that contains iron) levels were measured from 6 months through 10 years to determine children's iron levels. During the follow-up motor development test, IQ scores, spatial memory, reading and arithmetic skills, and visual-motor integration tests were carried out in order to examine the impact of iron-fortified products on neurobehavioral growth and development.

Children who were fed low-iron formula performed better in every test. Difference between kids in iron-fortified vs. low-iron group was significant for spatial memory and visual motor integration and suggestive for IQ, visual perception, and motor coordination tests.

Dr. Lozoff stated: “Children who entered the trial with high hemoglobin levels, suggesting iron sufficiency, showed poorer outcome if they received iron-fortified formula.” At the age of 10, IQ scores were on average 11 points lower for youngsters who were fed a high-iron formula, despite being iron sufficient.

Iron-fortified formulas are still commonly used around the world, however it seems these products have an adverse effect on long-term development if given to well-nourished children. Outcome was the poorest in children, who were most iron-sufficient at baseline. On the contrary, for children with low iron status, a high-iron formula is still likely to be beneficial, according to Dr. Lozoff.

The results of the study surprised the researchers, who believed that iron supplementation would lead to better health outcomes. Because of iron's potential toxicity in certain populations, many pediatric specialists agree that a lower range of about 4 to 7 mg/L of iron in formulas would be sufficient.

Breastfeeding is of course still the best choice for babies as it has many proven long term benefits and formulas should only be considered when breastfeeding is not possible or is insufficient.

Source: Neurodevelopmental Delays Associated With Iron-Fortified Formula for Healthy Infants