Quite a few studies have shown that breastfed infants show better cognitive functioning than their non-breastfed peers and these differences persist throughout childhood and into adolescence. Even when factors known to influence thinking and reasoning skills — such as birth weight, duration of gestation, and mother’s education and socioeconomic status — are taken into account, breastfed children continue to show better mental functioning.

But how soon does breastfeeding make a difference, and just how much of a difference does it make? Not every woman wants to breastfeed, and not every woman finds it possible to breastfeed.

I think it's astounding that you could have that much difference so early.

Because studies have found that the white matter in the brains of adolescents who were breastfed is thicker than in those who were not, and these physical differences are associated with improved IQ, researchers at Brown University recently investigated when these structural differences first appear in the brains of breastfed infants and how early the developmental differences among young infants can be seen.

Children from 10 months through four years old were divided into three groups. One group was exclusively breastfed for a minimum of three months; another exclusively formula fed; and a third fed a mixture of formula and breast milk.

The researchers took magnetic resonance imaging (MRI) scans of children's brains while they were sleeping and then looked at the microstructure of the brain’s white matter. White matter is nerve tissue that affects how the brain learns and functions. It acts to relay and coordinate communication between different brain regions.

The team found that children who were breastfed early and exclusively showed increased thickness of regions and neurological pathways of the brain associated with executive or higher order thinking functions including planning, social emotional functioning and language. Exclusive breastfeeding was also associated with increased development of brain regions involved in language performance, visual reception, and motor control.

When compared with children who received both breast milk and formula, children who were exclusively breastfed showed distinct increases in brain development specifically in areas which are linked to improved performance in tests of visual receptivness and receptive language. Infants who breastfed for longer than one year showed neurodevelopmental advantages over those infants who had breastfed for under one year.

“We're finding the difference [in white matter growth] is on the order of 20 to 30 percent, comparing the breastfed and the non-breastfed kids,” study author Sean Deoni, an assistant professor of engineering at Brown University, said in a university news release. “I think it's astounding that you could have that much difference so early.”

The researchers think that two omega-3 fatty acids found in components of breast milk, docosahexaenoic acid (DA) and arachidonic acid (AA), may prompt neural and white matter growth. They also note that the cholesterol present in breast milk may promote the development of myelin, the coating of nerve cells which makes faster communication of nerve impulses possible.

The study showed that the exclusively breastfed group had the fastest growth in myelinated white matter of the three groups, with the increase in white matter volume becoming substantial by age two. The group fed both breast milk and formula had more growth than the exclusively formula-fed group, but less than the breast milk-only group.

The fatty acids DA and AA are not presently contained in formula, so the infant’s system must synthesize them from their precursors. Similarly, formula has limited cholesterol content. These substances, which appear to be key to the developing central nervous system function, are more limited in availability in currently used infant formulas.

The researchers contend that their study is the first to show that brain changes promoted by breastfeeding occur very early in life. They believe their data underscore the critical need to support breast feeding and thus promote optimal infant develoment. The World Health orgnaization recommends that infants be breastfed for two or more years. The American Academy of Pediatrics recommends that infants be breastfed for at least 12 months.

The study is published in the journal, Neuroimage.