Your kids may not thank you for it, but new research reveals just what parents should feed their children to make them smarter.
And it's fish once a week and bread and cereals four times a day that make all the difference.
The findings come in a major New Zealand study into children's IQ levels, diets and family situations.
The study suggests that if children eat certain types of food their intelligence may be boosted or significantly lowered. It singles out margarine as having particularly strong links with lower IQ scores.
The thesis by University of Otago research fellow Dr Reremoana Theodore, calls for further research into margarine and says children from disadvantaged families could be most at risk as margarine is often cheaper than other spreads.
Richard Swinbourne, a dietitian who works with schools in the Taranaki region, says the findings need to be seen as part of a wider picture.
"You could have a child having margarine but if they were having a couple of bits of fruit a day, and going to school with breakfast, and physically active... I'm sure they would overshoot someone that wasn't having the margarine, alone."
The fish and bread findings make sense to Swinbourne but he also emphasises the importance of children eating breakfast. He says children form many permanent eating habits before they turn five so what parents eat in that time, and what they feed their child, will influence the child's diet for life.
Theodore's thesis looked at the IQs, diets and family situations of almost 600 New Zealand European children, as well as detailing the pregnancy of each mother. These families are still being tracked by the Auckland Birthweight Collaborative group of researchers, to investigate how children develop.
Theodore analysed the effect certain factors had on children's intelligence. She did not look at other health effects and warns that some of her more controversial findings should not be used to justify diets or behaviour that could be harmful in other ways.
For example, she found that mothers who drank moderate amounts of alcohol while pregnant had children with much higher IQs, than those who did not. But Theodore was unable to investigate the effects of binge-drinking, or drinking during the middle seven months of pregnancy. And the Alcohol Advisory Council says this result seems to be "at odds with the great body of evidence linking alcohol to poor health outcomes for the foetus".
The council's acting chief executive, Dr Andrew Hearn, points to a Ministry of Health study showing mothers who had one drink a week could change their child's behaviours, and one drink a day could damage the child's cognitive skills.
"There is no known safe level of consumption of alcohol during pregnancy and both Alac and the Ministry of Health advise pregnant women to avoid all alcohol," says Hearn.
Smoking tobacco during pregnancy has very little effect on the child's intelligence, Theodore found.
She wants her "surprising" finding about margarine to be treated with caution, because this is the first time the link has been made. But she found that after eliminating all other factors, children eating margarine daily have "significantly lower intelligence scores". Theodore wonders whether trans-fatty acids in margarine could be to blame, but dietitian Jacquie Dale says the make-up of margarines has changed since the research was conducted. "I don't think you'll find any with trans-fats, in New Zealand".
Dale says children don't need margarine, butter or other "blended" spreads on their sandwiches instead, parents should look for substitutes that are low in saturated fat, not overly processed and that contain some "goodies". Her suggestions include peanut butter, hummus, cottage cheese, a thin slice of cheese, or chutney.
Although Theodore's food and IQ findings have not yet been published by an academic journal (although manuscripts have been submitted for peer review and she expects them to be published soon) other important aspects of the thesis have.
These include a detailed snapshot of NZ pre-schoolers' diets, published in the New Zealand Medical Journal, revealing that 27% of pre-school children did not eat the recommended two or more servings of fruit a day, while 54% did not eat two or more servings of vegetables a day. Disturbingly, 93% of children did not eat breads and cereals the recommended four or more times a day.
Another article based on Theodore's thesis covering the non-dietary factors (such as parents' education and social support) that affect IQ has been approved for publication in a European paediatrics journal.
Dr Reremoana Theodore, now a research fellow at the University of Otago, wrote her thesis while studying at the University of Auckland. This thesis is part of the Auckland Birthweight Collaborative project which is tracking the development of babies born small, but at the "right" time. Theodore looked at NZ European families only, because many families of other ethnicities dropped out after a few years. The project started with 871 NZ European families but, by the time the children turned seven, that had dropped to 591. Only 5 percent of parents were of low socio-economic status. Two types of IQ tests were administered, by trained examiners, at Starship Children's Research Centre or sometimes at the family home. Mothers were surveyed shortly after giving birth and the families were surveyed in detail when the children were 312 and 7. Before concluding a factor was in itself significant, Theodore adjusted the raw results to make sure it was not influenced by other, linked factors.
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