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Friday 31 March 2023 Dublin: 10°C
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# Junk Food
Does a junk food diet lower children's IQ?
A new study found that a predominantly processed food diet at the age of three was associated with a lower IQ at the age of 8.5.

DOES A JUNK food diet lower a child’s IQ?

According to a new study by researchers at the University of Bristol, a diet, high in fats sugars, and processed foods in early childhood may lower IQ, while a diet packed full of vitamins and nutrients may do the opposite.

The results of the population-based cohort study was published online in the Journal of Epidemiology and Community Health.

The authors base their findings on participants in the Avon Longitudinal Study of Parents and Children (ALSPAC), which is tracking the long term health and wellbeing of around 14,000 children born in 1991 and 1992.

Parents completed questionnaires, detailing the types and frequency of the food and drink their children consumed when they were 3, 4, 7 and 8.5 years old.

Three dietary patterns were identified:

  • Processed: high in fats and sugar intake
  • Traditional: high in meat and vegetable intake
  • Health conscious: high in salad, fruit and vegetables, rice and pasta.

Scores were calculated for each pattern for each child.


The children had their IQ measured using a validated test when they were 8.5 years old.

The results showed that after taking account of potentially influential factors, a predominantly processed food diet at the age of three was associated with a lower IQ at the age of 8.5, irrespective of whether the diet improved after that age.

On the other hand, a healthy diet was associated with a higher IQ at the age of 8.5. The study found that dietary patterns between the ages of 4 and 7 had no impact on IQ.


The authors say that these findings, “although modest, are in line with previous ALSPAC research showing an association between early childhood diet and later behaviour and school performance”.

This suggests that any cognitive/behavioural effects relating to eating habits in early childhood may well persist into later childhood, despite any subsequent changes (including improvements) to dietary intake.

The brain grows at its fastest rate during the first three years of life, say the authors, adding that other research has indicated that head growth at this time is linked to intellectual ability.

They suggest that it is possible that good nutrition during this period may encourage optimal brain growth, and advocate further research on the subject.

Read: Smoking cannabis as a teenager lowers IQ – study>

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