People who are breastfed may have higher IQ scores and earn more money in the long-term, a new study has found.

According to researchers in Brazil, while the short-term benefits of breastfeeding are clear, the long-term benefits have yet to be established. They set out to assess whether breastfeeding was linked to IQ and income levels at the age of 30.

The study was started back in 1982 when information about breastfeeding among thousands of babies was gathered. Almost 3,500 babies were followed up when they reached 30 years of age.

The study found that those who were breastfed for at least 12 months had higher IQ scores, more years of education and a higher monthly income at the age of 30, compared to those who had been breastfed for less than one month.

These results stood irrespective of the socioeconomic status of the mother.

"Breastfeeding is associated with improved performance in intelligence tests 30 years later, and might have an important effect in real life by increasing educational attainment and income in adulthood," the reserachers suggested.

According to lead researcher, Dr Bernardo Lessa Horta of the University of Pelotas, the beneficial effects of breastfeeding on IQ are likely due to the presence of long-chain saturated fatty acids, known as DHAs, which are found in breast milk and are essential for the development of the brain.

Details of these findings are published in the journal, The Lancet Global Health.