Breastfeeding is smart -- but it doesn't produce smarter babies. Researchers have found there is no cause-and-effect relationship to explain the correlation between higher IQ and breastfeeding.

The reason for the link appears to be related to the education level of breastfeeding mothers and other background influences rather than to any ingredient in the milk.

Breastfeeding does provide children with many advantages, including lower incidence of infections, respiratory illnesses and diarrhea. However, it has little or no effect on intelligence, according to a report published in the BMJ.

Researchers at the UK's Medical Research Council and the University of Edinburgh analyzed data from 5,475 children and 3,161 mothers in the US.

They concluded that highly educated mothers are more likely to breastfeed than those with less education, and that breastfed babies are more often raised in mentally simulating surroundings.

When the researchers eliminated the mother's intelligence level from the analysis, there was no longer any link between a child's IQ and breastfeeding.

Even in cases where one sibling was breastfed and another was not, children in the same family tended to have similar mental capacities.