London: Breast-fed children are more intelligent than their bottle-fed counterparts.
However, this has nothing to do with the content of the milk they receive, a study published in the British Medical Journal said.
For decades scientists have been looking for a correlation between feeding and intelligence, but the report says genetic and environmental factors affect a child's intellect.
Researchers, who analysed data from more than 5,000 children and 3,000 mothers in the United States, found that mothers who breast-feed tend to be more intelligent, according to a study published Wednesday on the journal's Web site.
"When this fact was taken into account, most of the relationship between breast-feeding and the child's intelligence disappeared," one of the report's authors, Jeff Dar said.
"This research shows that intelligence is determined by factors other than breast-feeding," he added.
The report won't end the debate about the relationship between intelligence and breast-feeding.
"The problem is trying to show the impact of breast-feeding over and above outside variables," said Mike Woolridge, senior lecturer in infant feeding at the University of Leeds.
He said that other studies on the subject have claimed a link to intelligence.
"I fundamentally believe breast-feeding builds a better, more balanced brain in terms of its chemical composition and I'm sure you can measure that in terms of brain performance," Woolridge said.
The researchers found that children who were breast-fed did better on IQ tests, but this was because their mothers were more intelligent, better educated and able to provide a more stimulating home environment.
Part of the research methodology included testing pairs of siblings, for whom feeding habits differed.
"Comparing two people from the same family like this is a good way of getting results that are less affected by family background. This confirmed the earlier results — the breast-fed child was no more intelligent," Dar said.
Dr Chris Lucas, director of the Early Childhood Service at the New York University Child Study Center, praised the report for taking into account the impact of maternal intelligence on the findings.
"Intelligence is probably one of the most heritable things. Intelligence of a child is very much determined by the intelligence of the parents," he said.
"If you don't measure the mother's intelligence, it may appear that there is a link with breast-feeding,” he added.
Dar said that though his team's study found no link to intelligence, breast-feeding was "definitely the smart thing to do," because of other benefits to both mother and child, including a stronger ability to ward off infections, respiratory illnesses and protection against developing allergies.
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