Longer duration of breastfeeding is linked to higher IQ and greater earnings in adulthood, a new study has found.
“Our study provides the first evidence that prolonged breastfeeding not only increases intelligence until at least the age of 30 years but also has an impact both at an individual and societal level by improving educational attainment and earning ability,” said lead author Dr Bernardo Lessa Horta from the Federal University of Pelotas in Brazil.
The study followed a group of almost 3,500 newborns born in Pelotas, Brazil for 30 years.
Information on breastfeeding was collected in early childhood. Participants were given an IQ test at the average age of 30 years old and information on educational achievement and income was also collected.
The researchers divided the subjects into five groups based on the length of time they were breastfed as infants, controlling for 10 social and biological variables that might contribute to the IQ increase including family income at birth, parental schooling, genomic ancestry, maternal smoking during pregnancy, maternal age, birthweight, and delivery type.
While the study showed increased adult intelligence, longer schooling, and higher adult earnings at all duration levels of breastfeeding, the longer a child was breastfed for (up to 12 months), the greater the magnitude of the benefits.
For example, an infant who had been breastfed for at least a year gained a full four IQ points (about a third of a standard deviation above the average), had 0.9 years more schooling (about a quarter of a standard deviation above the average), and a higher income of 341 reais (USD 104) per month (equivalent to about one third of the average income level) at the age of 30 years, compared to those breastfed for less than one month.
“The likely mechanism underlying the beneficial effects of breast milk on intelligence is the presence of long-chain saturated fatty acids (DHAs) found in breast milk, which are essential for brain development,” Horta said.
“Our finding that predominant breastfeeding is positively related to IQ in adulthood also suggests that the amount of milk consumed plays a role,” Horta said.
The study is published in The Lancet Global Health journal.