Children who are breastfed and eat healthy food during childhood experience better physical development than children who eat poor diets. It has also been speculated that the consumption of quality food leads to a higher IQ, but few long-term studies have investigated this notion until now. Researchers at the University of Adelaide looked at the link between eating habits and IQ.
The study of more than 7,000 children showed that children who were eating a diet based on legumes, cheese, fruits and vegetables had a two point higher IQ at the age of eight compared to kids who ate mostly processed and refined products with a high-carbohydrate density.
Although there was only a small difference in IQ, it can be hypothesisez that a more controlled study would have led to a bigger difference. The healthy children in this study were definitely eating more nutritious food than the unhealthy group, but they were still consuming a fair amount of typical western food. Also, the study only looked at the diet at 12 and 24 months, not the remaining six years up until age eight.
Eur J Epidemiol. 2012 Jul;27(7):525-35. Epub 2012 Jul 19.
McDade, T.W., Rutherford J. , Adair, L, et al. Early origins of inflammation: microbial exposures in infancy predict lower levels of C-reactive protein in adulthood
Published online before print December 9, 2009, doi: 10.1098/rspb.2009.1795