The finding has thrown into doubt current medical practice of limiting food and fluid intake after birth to keep babies clinically stable.

A 16-year study by the Medical Research Council has demonstrated clearly for the first time that nutrition plays a key role in the early development of the brain, which is particularly rapid soon after birth.

The boys were sicker at birth than the girls, 25% required ventilation for more than seven days, compared with only 16% of the girls. This could indicate that early diet has a greater impact on the brain development of sicker children.

Professor Alan Lucas, of the Institute of Child Health based at Great Ormond Street Hospital, fed 424 premature babies a 'nutrition-enriched' pre-term formula or a standard infant formula for one month after birth.

It was found that those infants fed the standard formula instead of the nutrient-enriched 'pre-term formula' had reduced verbal IQ at seven-and- a-half to eight years of age.

This effect was found to be particularly notable in boys. Those fed standard formula had a verbal IQ 12.2 points lower on average than those fed the enriched formula.

Professor Alan Lucas on the implications of the research

The researchers also discovered that there was a higher incidence of cerebral palsy in those babies fed the standard formula.

It is unlikely that under-nutrition can cause cerebral palsy. A more likely explanation is that when a premature baby suffers brain damage, early under-nutrition could affect the brain's ability to compensate.

Profound effect

Current medical practice has been called into doubt

The study also has implications for current clinical care of premature babies.

Often new-born babies are given restricted amounts of food and fluid in an attempt to keep them clinically stable.

The results of this study clearly demonstrate the need to ensure, where possible, that high risk babies receive the nutritional intake they require.

Professor Lucas said: "This study provides a clear illustration that early nutrition of premature babies can have profound lifetime effects on brain development, suggesting the idea that diet during critical periods in early life may be of great importance for our health and performance as adults.

"We try very hard to feed premature babies well, and there is no doubt there has been an improvement in the nutrition of premature babies over the years.

"But the problem is that these babies are sick and we may have, on occasion, to withdraw food and fluid from them in order to keep them clinically stable. So we have a compromise.

"What our data does is to change the balance of risks. Now that we know that it matters in terms of these children's long term outcome to feed them at a level that is less than they require we have to factor that into the very complex situation."

Since the late 1980s most hospitals have not used standard infant formulas for feeding premature babies.

The two trial formulas differed in their contents of protein, energy, calcium, phosphorous, iron, zinc, copper and several other micronutrients, but not in quality of protein or fat.