Nutrition in the first weeks of life could have a profound impact on the way the brain develops, research suggests.
London researchers found preterm babies fed enriched formula milk in their first weeks consistently outperformed other premature babies in IQ tests.
Their latest study, published in Pediatric Research, shows the benefits continue into the teenage years.
It also found a particular part of the brain is better developed in those given the enriched milk.
The team from Great Ormond Street Hospital for Children and the UCL Institute of Child Health note that while nutrition has been linked with behaviour, their findings are among the first to show how early feeding may even alter brain structure.
Lead researcher Dr Elizabeth Isaacs said: "It is not clear whether this just relates to preterm infants, who have very specific development issues.
"But obviously a next question would be if there are any wider implications, both for feeding beyond those first few weeks, and for babies who are born at term."
Explaining the gap
Babies were given either standard formula, or a version enriched with extra protein, fat, calcium, phosphorous, iron, zinc, copper and several other micronutrients.
Other babies received "bank" breast milk - ie not from their own mothers, while others received a mix of bank milk and formula.
Whatever the comparison, the child who had received the enriched formula milk performed better.
At the age of seven or eight, the difference was particularly notable in boys: those fed the normal diet had a verbal IQ 12.2 points lower on average than those fed the enriched formula.
In the latest analysis, carried out when the babies were aged about 16, there was a wider gap between the girls fed the standard version and their enriched counterparts, of nine points, than there was between the boys, which had narrowed to seven.
But this time in addition to IQ tests, researchers also took scans of the children's brains in an attempt to explain these variations.
They found substantial differences between the two groups in the size of the caudate nucleus - a part of the brain associated with memory and learning.
They speculated that this could account for the differences seen, particularly given that there were no particularly striking variations in other key areas of the brain between the two groups.
These days many preterm babies are fed a highly-enriched formula milk.
It is unclear whether it is one or the combination of the many extra nutrients in this formula which accounts for the differences in development among premature babies.
Bliss, the premature baby charity, welcomed this latest research.
"These findings are potentially very interesting and could have an influence on current thinking about how, when and what to feed premature infants.
"The care that premature babies receive in their first few hours and days of life is crucial and will shape their future development and quality of life.
"Anything that improves outcomes for these vulnerable babies is very welcome."
About one in 10 babies in the UK is born prematurely.