Do Junk Food Be Makin Kids Stupid?

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A study recently published in the BMJ's Journal of Epidemiology and Community Health found a small but significant IQ difference between 8 year olds who had been raised largely on "junk food" diets, and those who had been fed a "health conscious" diet most of their lives.

The conclusion, published on Monday, comes from a long-term investigation into 14,000 people born in western England in 1991 and 1992 whose health and well-being were monitored at the ages of three, four, seven and eight and a half.

Parents of the children were asked to fill out questionnaires that, among other things, detailed the kind of food and drink their children consumed.

Three dietary patterns emerged: one was high in processed fats and sugar; then there was a "traditional" diet high in meat and vegetables; and finally a "health-conscious" diet with lots of salad, fruit and vegetables, pasta and rice.

When the children were eight and a half, their IQ was measured using a standard tool called the Wechsler Intelligence Scale.

Of the 4,000 children for which there were complete data, there was a significant difference in IQ among those who had had the "processed" as opposed to the "health-conscious" diets in early childhood.

The 20 percent of children who ate the most processed food had an average IQ of 101 points, compared with 106 for the 20 percent of children who ate the most "health-conscious" food.

"It's a very small difference, it's not a vast difference," said one of the authors, Pauline Emmett of the School of Social and Community Medicine at the University of Bristol.

"But it does make them less able to cope with education, less able to cope with some of the things in life." _France24_via_DiversityIsChaos

In this type of population study, it is important that as many potential "confounders" be identified and corrected for, as possible. Ethnicity and socioeconomic status are particular confounders for IQ. Without adequate adjustments and corrections for confounding at all stages of the study, the results will not be particularly reliable -- even with such a large number of subjects included.

The current study, based on the Avon Longitudinal Study of Parents and Children, uses data on children's diet reported by parents in food-frequency questionnaires at 3, 4, 7 and 8.5 years of age. Dietary patterns were identified using principal-components analysis and scores computed at each age. IQ was assessed using the Wechsler Intelligence Scale for Children at 8.5 years. Data on a number of confounders were collected, and complete data were available for 3966 children. _PaperAbstract

Are the results of this study meaningful? Correlation is not causation, particularly when so many factors come together to form a child's IQ score on any given testing day. Multiple IQ scores would be more helpful than a single score, and naturally every little detail of the study's methodology would need to be dissected. Still, 4,000 subjects can provide a study with a lot of "power." If the scores were adjusted and corrected for SES and ethnicity, the findings may be important.

As always, it should be noted that childhood IQ is likely to change as a person grows to adulthood. And in terms of life success, sound executive function (EF) of the frontal lobes is more important overall, than high IQ -- although both sound EF and high IQ together work better than either one singly. A pity that there is no single easy way to test for the many parameters of a sound EF.