An intelligence-boosting gene in newborn babies explains why breast-feeding can raise a child's IQ, scientists have found.
Children with a particular version of the gene perform significantly better in IQ tests if they have been breast-fed as infants. On average, breast-feeding adds seven extra points to their IQ scores, even after allowing for different social backgrounds.
The gene, known as FADS2, is closely involved in the way the body processes fatty acids in the diet.
Previous research has shown that long chain polyunsaturated fatty acids (Pufas) accumulate in the brain during the first months after birth. They are present in human breast milk, but not cow's milk, and have recently been added to infant formulas.
Pufas are thought to be important to childhood brain development because they are essential for the efficient transmission of nerve messages and help to promote the growth of nerve fibres.
The new research involved two long-term studies following the progress of more than 3,000 children in the UK and New Zealand. One, the Dunedin Multidisciplinary Health and Development Study, tracked the health and behaviour of 1,037 children born in New Zealand from the age of three. IQ was tested at ages seven, nine, 11 and 13 and DNA samples obtained from 97% of the participants when they reached adulthood.
The Environmental Risk (E-risk) Longitudinal Twin Study monitored the development of 2,232 British children, all twins, whose IQ was measured at age five. DNA was taken for analysis from 2,140 of the children.
In the New Zealand study, 57% of the children were breast-fed and IQ scores ranged from 55 to 147. A total of 48% of the UK children were breast-fed. Their IQ scores ranged from 52 to 145.
The DNA samples revealed that 90% of the children in the two study groups had at least one copy of the "C" version of FADS2 which yielded higher IQs if they were breast-fed. But breast-feeding had no effect on the 10% of children who had "G" versions of the gene.
The findings appear in the journal Proceedings of the National Academy of Sciences. They go some way towards settling the "nature versus nurture" debate over what has the greatest influence on child intelligence.
