British psychologist Avshalom Caspi, of King’s College London, and fellow collaborators studied two groups of children: 1,037 girls and boys born 34 to 35 years ago in New Zealand and still living there, and 2,232 girls and boys born 12 to 13 years ago and living in England.
By eliminating all extraneous factors, such as varied birth weight, socioeconomic groupings, mothers’ intellectual capabilities, the researchers were able to accurately test the intelligence of these children, either by recently being tested at ages 7, 9, 11, and 13 years as with the English children or from intelligence tests given to the New Zealand children about thirty years ago.
They found that the FADS2 gene helped to produce a more intelligent child. The gene helps in the break down of fatty acids within human milk. It comes in two forms, where one form is more efficient in breaking down fatty acids. If children carried one or two copies of the more efficient form of the FADS2 gene, then they displayed higher intelligence. However, this higher intelligence was only present if they were also regularly breast-fed during infancy.
In fact, children that contained the more efficient form of the FADS2 gene and were breast-fed in infancy, also had an IQ level that was six or seven points higher than other children.
The results of the study performed by the Caspi team will be presented in a future issue of the Proceedings of the National Academy of Sciences. It is already published online at PNAS as “Moderation of breastfeeding effects on the IQ by genetic variation in fatty acid metabolism”.
The co-authors of the study with Caspi include Benjamin Williams, Ian W. Craig, Barry J. Milne, Leonard C. Schalkwyk, Alan Taylor, Helen Werts, and Terrie E. Moffitt, all of the Institute of Psychiatry, King’s College London; and Julia Kim-Cohen, of Department of Psychology, Yale University, U.S.A.; and Richie Poulton, Dunedin School of Medicine, University of Otago, New Zealand.
The abstract of their paper states, “Children's intellectual development is influenced by both genetic inheritance and environmental experiences. Breastfeeding is one of the earliest such postnatal experiences. Breastfed children attain higher IQ scores than children not fed breast milk, presumably because of the fatty acids uniquely available in breast milk.”
They go on to say, “Here we show that the association between breastfeeding and IQ is moderated by a genetic variant in FADS2, a gene involved in the genetic control of fatty acid pathways. We confirmed this gene–environment interaction in two birth cohorts, and we ruled out alternative explanations of the finding involving gene–exposure correlation, intrauterine growth, social class, and maternal cognitive ability, as well as maternal genotype effects on breastfeeding and breast milk.”
Finally, they conclude by saying, “The finding shows that environmental exposures can be used to uncover novel candidate genes in complex phenotypes. It also shows that genes may work via the environment to shape the IQ, helping to close the nature versus nurture debate.”
As reported in Science News magazine, U.S. psychologist Jeremy R. Gray, Yale University (New Haven, Connecticut), stated, “An IQ advantage of 6 to 7 points is unquestionably large enough to have a real-world impact on individuals.” [Science News, November 10, 2007, page 291]