Children who eat junk food will grow up to have a lower IQ than those who regularly eat fresh, home-cooked cooked meals, a study reveals.

Childhood nutrition has long lasting effects on IQ, even after previous intelligence and wealth and social status are taken into account, according to the paper.

Researchers at the University of London looked at 4000 Scottish children, aged three to five, to find out if the type of main meal they ate each day had an impact on their cognitive ability and growth.

Parents with a higher socio-economic status said that they gave their kids meals prepared with fresh ingredients more often, which positively affected their IQ. Lower socio-economic status was linked to more fast food in a child’s diet, which led to lower intelligence.

Dr Sophie von Stumm, from the department of psychology at Goldsmiths, said: “It’s common sense that the type of food we eat will affect brain development, but previous research has only looked at the effects of specific food groups on children’s IQ rather than at generic types of meals.

The findings highlighted that differences in children’s meals were also a social problem.

“Mothers and fathers from less privileged backgrounds often have less time to prepare a freshly cooked meal from scratch for their children,” she said.

“These children score lower on intelligence tests and often struggle in school.

“Schools in less privileged areas must do even more to balance children’s diet, so that they can achieve their cognitive potential.

“It shows that the freshness and quality of food matters more than just being full, in particular when children are young and developing.”

Similar discoveries were made in an Australian study published in August. It found that while eating healthily can give a boost to intelligence, toddlers on a diet of drinks and sweets were less bright as they got older.

By the age of eight the kids who ate junk food had IQs up to two points lower than their healthy counterparts, according to the researchers from the University of Adelaide.

And an American study, published in the Journal of Epidemiology & Community Health in 2010, showed that children who consume junk food like pizza, chips and biscuits before the age of three may end up having lower IQs than children who ate home-cooked meals with fruit and vegetables.

These kids were tested five years later and had IQ scores that were as much as five points lower than their healthier-eating peers.

The researchers suspected the negative effect of eating junk food so early in life may not be altered by future healthy habits because brain development is hindered.