When it comes to intelligence, it seems breast really is best -- but only for children with a certain genetic make-up.

Scientists have identified a specific gene implicated in the link between breastfeeding and higher IQ in children, suggesting that biology -- and not just socio-economics -- is involved.

A study published Nov. 5 in the Proceedings of the National Academy of Sciences has found that a variant of a gene involved in metabolizing the fatty acids in breast milk determines whether children get an IQ boost from breastfeeding -- on average as much as seven points.

Previous research has shown that breastfed children have higher IQs than those who were bottle-fed. But it wasn't clear if the advantage was partly the result of other factors such as the mother's own IQ or socio-economic status, said study author Avshalom Caspi. In Western countries, women from higher socio-economic groups are more likely to breastfeed, he explained.

His study controlled for the mother's intelligence and social class, as well as for the children's birth weight and gestational age (other factors known to influence intelligence).

Caspi and his multi-disciplinary team analyzed data on 3,200 boys and girls from two birth cohorts -- 1,000 from New Zealand born in 1972-73, and 2,200 from Britain born in 1994-95. Both groups had their IQ tested using the Wechsler Intelligence Scale for Children.

In both countries, breastfed children had an IQ edge -- but only if they had a 'C' genotype on a gene called FADS2.

Breastfeeding had no effect in children who had a 'G' variant of the same gene, said Caspi, a child psychologist at King's College London.
 

About 90 per cent of the children in the study had a 'C' variant of the gene, meaning they were genetically predisposed to benefit from fatty acids present in breast milk in the form of DHA (docosahexaenoic acid) and AA or ARA (arachidonic acid). The implication is they would also have, therefore, missed out on a potential increase to their intelligence if they were not breastfed.

But breastfeeding is no guarantee of producing a baby Einstein. Caspi says the IQ difference they found is a relatively modest advantage. However, given the average IQ is 100, a gain of six or seven points can mean an average child could go from being smarter than 50 per cent of all other children, to being smarter than 66 per cent of all other children.

Although there are now infant formulas on the market with the DHA and AA fatty acids found to be beneficial in breast milk, Caspi said further study is needed to see whether his findings hold true for children fed formula supplemented with these nutrients.

Linda S. Gottfredson, an expert on intelligence at the University of Delaware, calls the study "exciting." On a population level, the implications are "huge," she said.

Even on an individual level, some children would see bigger IQ gains than the average of seven points Caspi and his colleagues found, she noted. If the gain were 10 or 15 points for some kids, that would translate into major benefits in real life -- for instance, the difference between flunking out of high school or graduating.
The advantage found by the breastfeeding study represents "an important IQ difference" and shows how breast milk helps raise IQ, said Dr. Reg Sauve, a professor of pediatrics at the University of Calgary and a spokesman for the Canadian Pediatric Society.

While previous studies showed a link between breastfeeding and higher intelligence, until now "nobody knew why this worked or how it provided this advantage."

In other news, a new study presented at a meeting of the American Heart Association found that breastfed babies are less likely to have certain cardiovascular disease risk factors in adulthood than their bottle-fed counterparts. The study, which included 393 mothers enrolled in the Framingham Offspring Study and 962 of their offspring, found that middle-aged adults who were breastfed as infants were 55 per cent more likely to have high HDL cholesterol (the "good cholesterol" that protects against heart disease and stroke) than those who were bottle fed.

Source : © CanWest News Service 2007