A 10-year study of 1,456 babies from the Isle of Wight found children who had been breastfed for at least four months had stronger lung function in later childhood.
A third of the children had been breastfed for at least four months, and on average, these children could blow out more air after taking a deep breath and could blow it out faster, according to researchers from the University of Southampton and the College of Veterinary Medicine in Michigan State University, US.
Writing in the journal Thorax, the scientists explained this could be because of the effort of sucking during breastfeeding.
Dr Syed Arshad, of the University of Southampton, said: "What they are doing is very similar to the kind of exercises we suggest for pulmonary rehabilitation in older patients.
"Breastfeeding for at least four months significantly increased lung function in later childhood and this effect was in addition to the reduction in wheeze, that was observed in the Isle of Wight birth cohort, in early childhood."
"The Isle of Wight has been used for many studies as it has a relatively static population. I am not at all surprised at these findings, I breastfed my son for seven months and he only developed asthma at 6 years old, despite a strong atopic family history. I hope with findings like this, more mothers will see the benefit of breastfeeding for longer." - Anne Evans, West Sussex