Poor childhood diet linked to low IQ, suggests study

By Nathan Gray

- Last updated on GMT

Related tags Nutrition

A diet high in fats, sugars, and processed foods in early childhood may result in lower IQ scores, while a diet rich in healthy foods packed with vitamins and nutrients may work in reverse, suggests new research.

The study, published in BMJ’s Journal of Epidemiology and Community Health​, reports a “weak but novel” ​association between dietary patterns in early childhood, and general intelligence assessed at eight and a half years of age.

The results of the study suggest that the eating habits in early childhood – particularly up until the age of three – may play a role in shaping the development of the brain, and thus affect behaviour, learning performance and IQ in later life.

“In this population of contemporary British children, a poor diet, associated with increased intake of processed foods, fat and sugar, in early childhood may be associated with lower IQ at the age of 8.5 years. In addition, a concurrent healthy diet may be associated with higher IQ,”​ said the researchers, led by Dr Kate Northstone from the Department of Social Medicine at the University of Bristol, UK.

The importance of healthy diets

Commenting on the new study, Barbara Gallani director of food safety and science at the UK’s Food and Drink Federation told FoodNavigator that it would not be surprising if a healthy, balanced diet is important in IQ development, “just like it is generally for children’s health and growth.”

She added that it is important for everyone, not just children, to eat a wide variety of foods, noting that it is possible eat a healthy diet and still include some ‘treat’ foods.

Gallani said that food manufacturers are leading the way when it comes to providing clear labelling on foods, as well as changing recipes to make old favourites healthier, which “makes it even easier for parents to choose a balanced diet that’s right for their families.”

An intelligent diet

Northstone and her colleagues noted that previous research investigating possible associations between nutrition and IQ in children have tended to focus on the use of dietary supplements or on intakes of specific nutrients.

For example, several studies have examined the effects of vitamin supplementation on IQ in children, with mixed results.

However, the authors said that studies investigating the long-term effects of nutrition on intelligence are sparse and conflicting. “In particular …there appears to be little known about the effects of the diet in early childhood on general intelligence later in life,”​ they said.

“We do not eat foods in isolation, rather consuming combinations of foods in meals and snacks,”​ explained the authors.

“Assessing dietary patterns as opposed to individual foods or nutrients allows to us take into account these intercorrelations, which may otherwise be overlooked,”​ they said.

The new cross sectional study, based on the Avon Longitudinal Study of Parents and Children (ALSPAC), examined the links between dietary patterns through early and mid-childhood (3 to 8.5 years) and IQ assessed at 8.5 years of age.

Study details

The researchers measured dietary patterns using principal-components analysis (PCA), which provide overall summaries of dietary intake. The diet data, measured at the ages of 3, 4, 7 and 8.5 was then examined for any associations between diet and IQ in nearly 4,000 children.

Three consistent dietary patterns were found from PCA at each time point: a ‘processed’, ‘traditional’ and ‘health conscious’ pattern.

The ‘processed’ pattern was illustrated by foods containing high fat and sugar content and by higher intakes of processed and convenience foods. The ‘traditional’ pattern was associated with consumption of generally home cooked meat, poultry, potato and vegetables, whilst the ‘health-conscious’ pattern was predominantly made up from high intakes of salads, fruit, vegetables, fish, pasta and rice.

“On minimal adjustment, all dietary pattern scores were associated with IQ with the exception of the ‘traditional’ pattern,”​ said the authors.

Before adjustment for confounding factors (such as parental influence, social and economic status, and other environmental factors) the researchers observed that the ‘processed’ food pattern was negatively associated with IQ at all ages, while the ‘health-conscious’ pattern at all ages were positively associated with IQ.

However, after adjustment for a wide variety of potential confounding factors, they reported that many associations between IQ and dietary pattern were lost, and those that remained (‘processed’ pattern at three years and ‘health-conscious’ patterns at 8.5 years) “were markedly attenuated”​, according to the authors.

For the remaining relationships (after full adjustment) the ‘processed’ food pattern at 3 years was found to be such that a one point increase in the PCA score resulted in an almost two-point decrease in IQ at 8.5 years. Whilst the ‘health-conscious’ pattern was associated with an increased in IQ of 1.20 points per one point increase in PCA pattern score.


Northstone and colleagues said that the results of the study suggest a more “long-term effect of diet on the child’s ability to ‘learn’,”​ they noted that this could be in part be explained by favourable growth of the brain in early childhood – They noted that it is known that the brain grows at its fastest rate during the first 3 years of life.

“Studies have shown that head growth during this time is associated with cognitive outcome, and it is possible that good nutrition during this early period may encourage optimal brain growth,”​ said the authors.

However, they added that given the levels of attenuation seen in the effect sizes when adjusted for confounding factors, “we cannot exclude the possibility of residual confounding.”

Source: Journal of Epidemiology and Community Health
Published online ahead of print, doi: 10.1136/jech.2010.111955
“Are dietary patterns in childhood associated with IQ at 8 years of age? A population-based cohort study”
K. Northstone, C. Joinson, P. Emmett, A. Ness, T. Paus

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