Researchers from the University of Adelaide found children fed healthy diets may have a slightly higher IQ, while those on heavier junk food diets may have a slightly reduced IQ.
Dr Lisa Smithers from the Public Health department in the University looked at the link between the eating habits of children at six months, 15 months and two years, and their IQ at eight years of age.
The study of more than 7000 children compared a range of dietary patterns, including traditional and contemporary home-prepared food, ready-prepared baby foods, breastfeeding, and 'discretionary' or junk foods.
"Diet supplies the nutrients needed for the development of brain tissues in the first two years of life, and the aim of this study was to look at what impact diet would have on children's IQs," Smithers said.
"We found that children who were breastfed at six months and had a healthy diet regularly including foods such as legumes, cheese, fruit and vegetables at 15 and 24 months, had an IQ up to two points higher by age eight," Smithers added.
"Those children who had a diet regularly involving biscuits, chocolate, sweets, soft drinks and chips in the first two years of life had IQs up to two points lower by age eight," Smithers said in a statement.
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"We also found some negative impact on IQ from ready-prepared baby foods given at six months, but some positive associations when given at 24 months," Smithers said.
"While the differences in IQ are not huge, this study provides some of the strongest evidence to date that dietary patterns from six to 24 months have a small but significant effect on IQ at eight years of age," Smithers said.
The study was published in the European Journal of Epidemiology.