Breastfeeding could help make your kids smarter, according to a new study.

At least, that's what researchers found after following a group of nearly 3,500 newborns for 30 years. It turns out that longer duration of breastfeeding is linked with a higher IQ in adulthood, longer schooling, and even earning more at your job.

What's more, the longer a mother breastfed for, the greater the benefits were.

"The effect of breastfeeding on brain development and child intelligence is well established, but whether these effects persist into adulthood is less clear," lead author Dr. Bernardo Lessa Horta, from the Federal University of Pelotas in Brazil, explained in a press release.

"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," he added.

Previous studies on breastfeeding mostly focused on those from lower socioeconomic classes, but this time researchers included women that were highly educated, made a high income, and were of different social classes.

Horta and his colleagues analyzed data from a prospective study of nearly 6,000 infants born in Pelotas, Brazil in 1982. They collected information on breastfeeding during early childhood, educational achievement and income during adults years. Participants were given an IQ test, based on the Wechsler Adult Intelligence Scale, when they reached an average of 30 years old.

The team also took into account factors such as genomic ancestry, maternal smoking during pregnancy, maternal age and birthweight.

Breastfeeding in general, no matter for how long, was associated with increased adult intelligence, longer schooling, and higher adult earnings. But what the researchers also realized was that these benefits were magnified the longer a child was breastfed for (up to 12 months).

For example, an infant who had been breastfed for at least a year gained a full four IQ points, had 0.9 years more schooling, and a higher income of 341 Brazilian real (about 106 US dollars) per month at age 30.

So what is it that makes breastfeeding so beneficial? Horta and his team speculate that it's because of long-chain saturated fatty acids (DHAs) that are 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," Horta said.

The hope is that future studies support this theory, and better explain the effects breastfeeding has on kids later in life.

The results were published in the journal The Lancet Global Health.

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