According to new research, that’s if the suckling infant has a certain version of a gene that helps process fatty acids
The genetic marker that Moffitt refers to is located in the FADS2 gene, which has two primary variations. The new study, based on 1,000 New Zealander children (a portion of whom were breastfed) in the early 1970s as well as on more than 2,000 breastfed kids who lived in the U.K. in the mid 1990s, showed that 90 percent of the subjects had at least one copy of the more common version of FADS2 and 50 percent of them had two copies.
The researchers found that breastfed infants with at least one or more of the common variation had IQ scores that were, on average, six to seven points higher than those of non-nursed kids with similar genetics. But breastfeeding did not appear to affect those children (10 percent of the population) with only the less common variant. The scientists ruled out other factors, including birth weight and the mother’s social class and IQ, finding that they had no impact.
“Those who were breastfed scored on average three points above the population mean of 100 on the IQ test, whereas those who were not breastfed scored about three points below the population mean,” Moffitt says. In other words, breastfeeding led to a gain of a few IQ points, whereas those using baby formula in lieu of mom’s milk led to a slight dip.
As for the study’s implications on nature / nurture debate, Linda Gottfredson, a professor of education at the University of Delaware, says that a person’s DNA is not really a blueprint, as it is commonly portrayed. “[Genes] are more like playbooks,” she says. “It’s not nature or nurture, but your genes operate frequently by making you more susceptible or less susceptible to certain environmental conditions.” Hence, the withdrawal of breast milk from the diets of babies with a certain genetic predisposition resulted in a negative effect on intelligence.
The exact mechanism by which the enzyme coded by FADS2 might influence IQ is not known, but Moffitt suggests two possible roles: The gene variants may affect the conversion of dietary precursors to long-chain polyunsaturated fatty acids, which aggregate in the brain in the early months after birth. Alternatively, the presence of long-chain polyunsaturated fatty acids may act on the gene itself, causing it to turn on or off, thereby affecting the metabolic pathway the acids used.
The authors note that since the time that study subjects were breastfed, many baby formula manufacturers have begun adding fatty acid supplements to their products, potentially giving them an IQ boosting effect.
“What’s critical about this paper is that we haven’t known entirely what are the mechanisms by which breastfeeding supports higher IQ,” says Joseph Hibbeln, lead clinical investigator at the Unit of Nutrition in Psychiatry at the National Institute on Alcohol Abuse and Alcoholism. “This really helps to dissect one of those mechanisms: that is…, if your body can’t make [fatty acids] efficiently, you better get it through the breast milk to support optimal IQ.”
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