Lab Notes: Is fast food making children stupid? Don't swallow the stories


Junk food rots your brain, scientists say. Well, actually, I just made that up. What scientists have really shown is that feeding junk food to young children from the age of three "may be associated" with a slightly lower IQ score at the age of eight.

Words are as important in science as in a court of law. As any good epidemiologist will point out, given 0.5 the chance, association does not automatically mean causation. Because one event (junk food in early life) can be tied statistically to another (slightly lower IQ five years later), it doesn't necessarily follow that one causes the other.

The study in question, published last week in the Journal of Epidemiology and Community Health, was carried out as part of the Avon Longitudinal Study of Parents and Children (Alspac), which is tracking the long-term health and well-being of some 14,000 children born in 1991 and 1992.

Scientists at the University of Bristol wanted to test the hypothesis that a more "healthy" diet in childhood would be associated with an increase in intelligence. They wanted to see whether there was a difference in IQ scores between children fed on a diet rich in salads, pasta, rice, fish and fruit, and children given processed food with high fat and sugar content, such as crisps, fizzy drinks, chips and burgers.

The trouble with such studies is the influence of confounding factors. A mother (and it is usually the mother) who feeds her children a health-conscious diet may also be more likely to be a woman who reads to her kids at bedtime. So is it the diet, or the reading at bedtime that makes those children bright in later childhood? Or is it neither?

The scientists behind the study obviously tried to take such confounding factors into account by "controlling" for social class, maternal age at birth, type of housing, and maternal education. But even so, there is always the nagging possibility that a bad diet is just a marker for something else that really is affecting a child's intellectual development.

It may be, for instance, that a mother's intelligence, which has a heritable component, is linked with the likely diet of her children. Interestingly, this study did not control for maternal intelligence, though the authors of the study believe that controlling for maternal education should have eliminated this as a confounding factor.

Another potential source of error is the nature of the questionnaires used to assess the diet of the children. The mothers were asked to complete "food frequency" forms at the age of three, four, seven and eight-and-a-half years.

An intelligent mother may have filled in the form in a less-than-honest way, perhaps reflecting her health-conscious intentions rather than the actual reality – processed foods may be more convenient for a busy mum who is aware that it may not look too good if she is seen to be relying on them too much.

So it is perhaps easy to see why the scientists used carefully phrased words to conclude their scientific paper: "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."

Interestingly, the title of the paper is even more circumspect: "Are dietary patterns of childhood associated with IQ at 8 years of age?"

This headline went through an intriguing evolution in the course of its development from press release ("Processed-food diet in early childhood may lower subsequent IQ") to splash headline in the Daily Mail: "Junk food diet hits a child's IQ"). But the one thing that this study has not yet shown is that junk food lowers a child's IQ.

peopleFrankie Boyle responds to referendum result in characteristically offensive style
Life and Style
Couples have been having sex less in 2014, according to a new survey
New Articles
i100... with this review
Holly's review of Peterborough's Pizza Express quickly went viral on social media
footballTim Sherwood: This might be th match to wake up Manchester City
Arts and Entertainment
musicHow female vocalists are now writing their own hits
New Articles
ebooksAn unforgettable anthology of contemporary reportage
Arts and Entertainment
musicBiographer Hunter Davies has collected nearly a hundred original manuscripts
Blahnik says: 'I think I understand the English more than they do themselves'
Arts and Entertainment
Michelle Dockery as Lady Mary Crawley in Downton Abbey
TVInside Downton Abbey series 5
Life and Style
The term 'normcore' was given the oxygen of publicity by New York magazine during the autumn/winter shows in Paris in February
fashionWhen is a trend a non-trend? When it's Normcore, since you ask
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Marketing Manager - Leicestershire - £35,000

£30000 - £35000 per annum: Ashdown Group: Marketing Manager (CIM, B2B, MS Offi...

Marketing Executive (B2B and B2C) - Rugby, Warwickshire

£22000 - £25000 per annum: Ashdown Group: A highly successful organisation wit...

SEN Coordinator + Teacher (SENCO)

£1 per day: Randstad Education Leeds: Job Purpose To work closely with the he...

Research Manager - Quantitative/Qualitative

£32000 - £42000 Per Annum: Clearwater People Solutions Ltd: Our client is curr...

Day In a Page

Scottish referendum: The Yes vote was the love that dared speak its name, but it was not to be

Despite the result, this is the end of the status quo

Boyd Tonkin on the fall-out from the Scottish referendum
Manolo Blahnik: The high priest of heels talks flats, Englishness, and why he loves Mary Beard

Manolo Blahnik: Flats, Englishness, and Mary Beard

The shoe designer who has been dubbed 'the patron saint of the stiletto'
The Beatles biographer reveals exclusive original manuscripts of some of the best pop songs ever written

Scrambled eggs and LSD

Behind The Beatles' lyrics - thanks to Hunter Davis's original manuscript copies
'Normcore' fashion: Blending in is the new standing out in latest catwalk non-trend

'Normcore': Blending in is the new standing out

Just when fashion was in grave danger of running out of trends, it only went and invented the non-trend. Rebecca Gonsalves investigates
Dance’s new leading ladies fight back: How female vocalists are now writing their own hits

New leading ladies of dance fight back

How female vocalists are now writing their own hits
Mystery of the Ground Zero wedding photo

A shot in the dark

Mystery of the wedding photo from Ground Zero
His life, the universe and everything

His life, the universe and everything

New biography sheds light on comic genius of Douglas Adams
Save us from small screen superheroes

Save us from small screen superheroes

Shows like Agents of S.H.I.E.L.D are little more than marketing tools
Reach for the skies

Reach for the skies

From pools to football pitches, rooftop living is looking up
These are the 12 best hotel spas in the UK

12 best hotel spas in the UK

Some hotels go all out on facilities; others stand out for the sheer quality of treatments
These Iranian-controlled Shia militias used to specialise in killing American soldiers. Now they are fighting Isis, backed up by US airstrikes

Widespread fear of Isis is producing strange bedfellows

Iranian-controlled Shia militias that used to kill American soldiers are now fighting Isis, helped by US airstrikes
Topshop goes part Athena poster, part last spring Prada

Topshop goes part Athena poster, part last spring Prada

Shoppers don't come to Topshop for the unique
How to make a Lego masterpiece

How to make a Lego masterpiece

Toy breaks out of the nursery and heads for the gallery
Meet the ‘Endies’ – city dwellers who are too poor to have fun

Meet the ‘Endies’ – city dwellers who are too poor to have fun

Urbanites are cursed with an acronym pointing to Employed but No Disposable Income or Savings
Paisley’s decision to make peace with IRA enemies might remind the Arabs of Sadat

Ian Paisley’s decision to make peace with his IRA enemies

His Save Ulster from Sodomy campaign would surely have been supported by many a Sunni imam