Feeding your infants with extra iron when they don't need it might hinder their development, says a new study.
The new study from University of Michigan on 494 Chilean children has sparked off debate over optimal iron supplement levels.
"Our results for 25 years of research show problems with lack of iron. For us to find this result is a big deal, it's really unexpected," said Dr. Betsy Lozoff, principal investigator and research professor at the Centre for Human Growth and Development.
US infant formulas typically come fortified with 12 mg/L of iron to prevent iron-deficiency anaemia. Europe generally uses a lower amount.
Iron-deficiency anaemia is linked to poorer development, and during pregnancy it contributes to anaemia in mothers, contributing to premature birth, low birth weight and other complications.
"I thought that behaviour and development would be better with the 12 mg formula," said Lozoff, also professor of pediatrics in the U-M Department of Pediatrics and Communicable Diseases at the Medical School and C.S. Mott Children's Hospital.
The findings revealed those who received iron fortified formula in infancy at the 12 mg used in the US lagged behind those who received low-iron formula in cognitive and visual-motor development by age 10 years.
Lozoff stressed that most children who received the 12 mg formula did not show lower scores. But the 5 percent of the sample with the highest haemoglobin levels at 6 months showed the poorest outcome.
The body needs iron to make haemoglobin, a substance in red blood cells that enables them to carry oxygen. High haemoglobin generally indicates sufficient iron.
The most affected children scored 11 points lower in IQ and 12 points lower in visual-motor integration, on average; the average overall score on both tests was 100. A similar pattern was observed for spatial memory and other visual-motor measures.
Lozoff said that iron deficiency occurs because babies grow so quickly they often "grow out" of the amount of iron they are born with. Breast milk is thought to contain the iron a baby needs for 4-6 months.