Babies born prematurely grow stronger hearts if they are breastfed, research has shown.
A study found that adults who were born early had reduced heart volumes and function compared with those who were not.
But the damage was significantly less in those who as infants had been fed exclusively on breastmilk.
For individuals who had received a combination of feeding methods, heart structure and function improved the more breastmilk they were given.
Lead scientist Dr Adam Lewandowski, from Oxford University, said: "Even the best baby formula lacks some of the growth factors, enzymes and antibodies that breastmilk provides to developing babies.
"These results show that even in people whose premature birth has inevitably affected their development, breastfeeding may be able to improve heart development."
The heart changes are thought to emerge in the first few months after birth.
The Oxford team, whose findings appear in the journal Pediatrics, already had data on more than 900 adults who had taken part in a study of different feeding regimes in pre-term infants.
Of those, 102 men and women now in their early to mid-twenties were invited to take part in a more detailed heart study.
They were compared with another group of 102 people who had not been born prematurely.
Commenting on the results, Professor Russell Viner, from the Royal College of Paediatrics and Child Health, said: "This is an exciting piece of research which adds to the wide-ranging benefits that are already known about breastmilk.
"For premature babies, who are born before they are physically ready for life outside the womb, breastmilk is incredibly important. It protects an already vulnerable baby from infections and leads to a range of later beneficial effects on the brain, blood pressure and bone strength.
"This research suggests that the benefits also extend to improved development of the heart."