Researchers examining the relationship between breastfeeding and higher IQ test scores in later life have uncovered a link with a gene responsible for modifying fatty acids in the diet.

It is known that people who are breastfed as babies achieve, on average, higher scores in IQ tests later in life. Now a team led by Avshalom Caspi from the Institute of Psychiatry at King’s College London in the UK has found that those with a variant form of a gene called FADS2, which encodes an enzyme involved in fatty acid metabolism, do not benefit from this breast milk-related IQ boost.

The research adds weight to the idea that long-chain polyunsaturated fatty acids in breast milk - principally docosahexaenoic acid and arachidonic acid - are important for the development of brain cells in the feeding infant.

’There is healthy scepticism about whether breastfeeding really improves IQ, because science has not explained how breast milk could have an effect on the brain,’ said Terrie Moffitt, one of the researchers. ’One hypothesis focuses on the nutritional content of breast milk. Our finding supports this possible mechanism. Fatty acids in breast milk may be the raw material for a genetically-guided process that fosters optimal newborn brain development.’ 

The researchers surveyed 1000 children in New Zealand and 2200 in the UK. They found that on average children who had been breastfed had a higher IQ score of 6 to 7 points. However, breastfed children with the variant form of FADS2 did not benefit. The study ruled out other potentially confounding factors, such as social class, birth weight or the IQ score of the mother.

But precisely how the genetic variation in FADS2 might guide the processing of nutrients in breast milk to alter brain development is not clear.

Lawrence Whalley of the University of Aberdeen, UK, an expert on the effects of nutrition on cognitive development, told Chemistry World, ’These findings are among the first to reveal gene-nutrient interactions in cognitive development.’

Whalley added that, as suggested by the researchers, future trials of food supplements - whatever the age group studied - should include identification of sub-samples who may be genetically predisposed to benefit from the extra nutrient.

Simon Hadlington