According to the study, this effect of nutrition and IQ is particularly true during the first three years of life when the brain is developing rapidly. The researchers speculate that good nutrition may promote brain growth and cognitive development.
"We have found some evidence to suggest that a diet associated with increasing consumption of foods that are high in fat, sugar and processed foods in early childhood is associated with small reductions in IQ in later childhood," said lead researcher Kate Northstone, a research fellow in the department of social medicine at the University of Bristol. A more health-conscious diet was associated with small increases in IQ.
Children should be encouraged to eat healthy foods from an early age, said Northstone. "We know this is important for physical growth and development, but it may also be important for mental ability," Northstone added.
Nutrition, IQ and Brain Health
For the study, Northstone's team collected data from the Avon Longitudinal Study of Parents and Children on 3,966 children born in 1991 and 1992.
The children's parents had answered questions about their kids' diets at age 3, 4, 7 and 8.5 years. The children's IQs were measured using the standard Wechsler Intelligence Scale for Children when they were 8.5 years old.
The researchers identified three basic diets: a "traditional" diet high in meats and vegetables; a "health conscious" diet with lots of fruit, vegetables, salads, fish, rice and pasta, and a "processed" diet high in fats, sugar and convenience foods.
Children who ate a diet high in processed foods at age 3 had a lower IQ at 8.5 years than kids with a healthy diet. For every one point increase in processed foods consumption, they lost 1.67 points in IQ. Conversely, the researchers found that every point increase in healthy eating translated into a 1.2 point increase in IQ.
The key seemed to be the diet at age 3, since diet at 4 and 7 seemed to have no effect on IQ, the research team noted. However, to truly understand the effect of diet on children's intelligence, further studies are needed.
SOURCES: Kate Northstone, Ph.D., research fellow, department of social medicine, University of Bristol, Bristol, England; Feb. 7, 2011, Journal of Epidemiology and Community Health