The research data originated from a prospective study of nearly 6000 infants born in Pelotas, Brazil in 1982. The scientists collected available Information on breastfeeding. Participants were given an IQ test (Wechsler Adult Intelligence Scale, 3rd version) at the average age of 30 years old and information on educational achievement and income was participants. 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, birth-weight, and delivery type.
Information on IQ and breastfeeding was available for just over half (3493) participants. The researchers divided these 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.
The research findings revealed that the longer a child was breastfed for (up to 12 months), the greater the increase in benefits. A child 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 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 effect of breastfeeding on brain development and child intelligence is well established, but whether these effects persist into adulthood is less clear,” said lead author Dr Bernardo Lessa Horta from the Federal University of Pelotas in Brazil. “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. What is unique about this study is the fact that, in the population we studied, breastfeeding was not more common among highly educated, high-income women, but was evenly distributed by social class. Previous studies from developed countries have been criticized for failing to disentangle the effect of breastfeeding from that of socioeconomic advantage, but our work addresses this issue for the first time.”
“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. Our finding that predominant breastfeeding is positively related to IQ in adulthood also suggests that the amount of milk consumed plays a role,” said Dr. Horta.
Cesar G Victora, Bernardo Lessa Horta, Christian Loret de Mola, Luciana Quevedo, Ricardo Tavares Pinheiro, Denise P Gigante, Helen Gonçalves, Fernando C Barros. Association between breastfeeding and intelligence, educational attainment, and income at 30 years of age: a prospective birth cohort study from Brazil. The Lancet Global Health, 2015; 3 (4): e199 DOI: 10.1016/S2214-109X(15)70002-1