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Higher IQ found in breastfed babies if the right gene is present

NOVEMBER 06, 2007

Researchers at the Institute of Psychiatry, King’s College London, have discovered that breastfeeding can have a positive effect on the IQ of children when combined with the right genes.   Based on two studies of breast-fed infants involving more than 3,000 children in Britain and New Zealand, Breastfeeding was found to raise intelligence by an average of nearly 7 IQ points if the children had a particular version of a gene called FADS2.

The known association between breast feeding and slightly higher IQ in children is shown to relate to this particular gene in the babies and the findings are published on-line today in the Proceedings of the National Academy of Sciences in the US. 

Lead author Avshalom Caspi and colleagues Ben Williams, Ian Craig and Terrie Moffitt at King’s College London, collaborated with colleagues from the University of Otago, New Zealand, together with Duke University and Yale University in the US.

Professor Terrie Moffitt, a co-author on the paper at the MRC Social, Genetic and Developmental Psychiatry Centre at King’s College London, said: “There has been some criticism of earlier studies about breastfeeding and IQ saying that they didn't properly control for socioeconomic status, or the mother's IQ or other factors, but our findings give a fresh perspective different from those arguments by showing a physiological mechanism that could account for the difference."

The researchers found that the baby's intellectual development was influenced by both genes and environment or, more specifically, by the interaction of its genes with its environment.  Moffitt continued: “The argument about intelligence has been about nature versus nurture for at least a century.  However we have shown that infact nature works via nurture to create better health outcomes.  In this case the environment is breastfeeding, the gene is the FADS2 gene, and the outcome is better cognitive function."

The FADS2 gene is inherited from both the mother and father’s side and comes in two versions: C and G.  Ninety percent of the children in the two study groups had a "C" version of FADS2, which yielded higher IQ if they were breast-fed. The other 10 percent, with only the "G" version of the gene, showed no IQ advantage or disadvantage from breastfeeding.  

The gene was singled out for the researchers' attention because it produces an enzyme that helps convert dietary fatty acids into the DHA (docosahexaenoic acid) and AA (arachidonic acid) polyunsaturated fatty acids that have been shown to accumulate in the human brain during the first months after birth.

The first findings about breastfeeding and IQ appeared over a decade ago, and in the past 10 years many formula makers have added DHA and AA fatty acids to their products. The children in these studies however were born in 1972-73 in New Zealand and 1994-95 in England, before fatty acid supplementation in formula began.

Though the jury is still out on whether such supplementation has made a difference in humans, laboratory studies in which rodents and primates were fed supplemental fatty acids have shown increased brain DHA concentrations and enhanced abilities in tests of learning, memory and problem-solving. 

"Our findings support the idea that the nutritional content of breast milk accounts for the differences seen in human IQ," Moffitt remarked "But it's not a simple all-or-none connection: it depends to some extent on the genetic makeup of each infant."

Moffitt noted that the researchers were not especially interested in IQ or breastfeeding per se, but that the study fitted into a body of work they have done on gene-environment interactions and the brain. 

She concluded:  “What we are really interested in proving to the mental health community is that genes often influence behaviour through sensitivity to environments.  When looking at genetic effects on depression, violence, schizophrenia, or intelligence, the key bit that's often left out here is the environmental effects."

The research was supported by the National Institute of Mental Health (US), the Medical Research Council (UK), the Health Research Council (New Zealand) and the Royal Society-Wolfson Research Merit Award (UK).

Notes to editors
1. A full copy of the paper ‘Nature, Nurture and the IQ: Moderation of breastfeeding effects on the IQ by genetic variation in fatty acid metabolism’ can be downloaded PNAS website at The embargo is lifted at 9pm GMT on Monday 5th November 2007.
2. The research team comprised: King’s College London, Medical Research Council Social, Genetic, and Developmental Psychiatry Centre, Institute of Psychiatry, SE5 8AF; University of Otago, Dunedin School of Medicine, Dunedin, New Zealand; Duke University, Departments of Psychology & Neuroscience, and Psychiatry & Behavioral Sciences, and Institute of Genome Sciences of Policy, Durham, North Carolina, 27708-0086, USA; Yale University, Department of Psychology.
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