Iron deficiency is our most common nutritional deficiency. When infants and young children are iron deficient, the effects can be significant and long-lasting.

Low birth weight infants are at particular risk for iron deficiency, and a new study suggests that a little extra iron in the first six months of life may ward off behavioral problems down the road.

The Swedish study examined the effects of supplemental iron on 285 late preterm and term babies who weighed between 4.4 and 5.5 pounds. Some of the infants received iron supplements from the time they were six weeks old until they were six months old, while others did not receive any.

There was less iron deficiency anemia among the six-month-old infants who were given iron supplements, and by time they were 3½ years old those toddlers showed fewer behavioral issues compared to those who had not been given extra iron in infancy.

Researchers tested 207 of the original infants again at the age of seven years for their cognitive and neurobehavioral abilities. Parents completed questionnaires about their children’s behavior, and the children were assessed using the Wechsler Intelligence Scale for Children.

The findings suggest that low birth weight children who do not receive adequate iron in infancy may go on to have neurodevelopmental problems that go unnoticed until there is a diagnosis such as ADHD or autism.

Iron plays an important role in the development of a baby’s brain, particularly during the last trimester of pregnancy when considerable brain tissue development occurs.

The intelligence scores between the two groups of children weren't particularly different, but there were some important behavioral and cognitive differences between the two groups. Children who had received iron supplementation as infants showed much less aggression, were less prone to rule-breaking behavior, and experienced fewer thought problems than did low birth weight children not given supplemental iron.

The sorts of thought problems noted in study participants who were not given iron supplementation have been shown to be independent predictors of autism spectrum disorders, suggesting that low birth weight children who do not receive adequate iron in infancy may go on to have neurodevelopmental problems that go unnoticed until there is a diagnosis such as ADHD or autism.

“Our findings suggest that iron supplementation may have long-lasting effects on behavioural functions in children born of a low birth weight,” said lead researcher, Staffan Berglund, of Umeå University in Sweden, in a statement. “This clinically important benefit from early iron supplementation gives further support to recommend iron supplementation of all low birth weight children, including those with marginally low birth weight.”

It is possible for babies to be given too much iron, but the findings are still significant given the fact that as many as five percent of babies born in high income countries and up to 15 percent of those born in low income countries are defined as marginally low birth weight.

The study was published in Pediatric Research.