A study of Brazilians found that young adults who had breast-fed as babies had higher incomes and IQs.
Researchers tracked down nearly 3,500 Brazilian adults who were enrolled in a study soon after their births in 1982. Interviewers had asked their mothers how long their children were breast-fed.
At the time, breast-feeding wasn't associated with any particular socioeconomic class in Brazil, the study authors said.
By 2012, the children were 30-year-olds with jobs.
Compared to those who stopped breast-feeding by the time they were a month old, those who nursed for more than a year earned 28 percent more per month, the study found. Incomes were 39 percent higher for those who nursed for six months to one year.
After adjusting for demographic factors, the researchers calculated that study participants who nursed for six to 12 months averaged 3.5 IQ points higher than those who nursed for less than a month.
The results were published in the journal Lancet Global Health.