Junk Food and Childhood Asthma: What the Half-Million-Child Isaac Study Found

Children who eat fast food three or more times a week appear more likely to suffer severe asthma, hay fever, and eczema. That is the finding of one of the largest studies of children's diet and allergic disease ever conducted. But the phrase linked to is doing heavy lifting in that sentence, and the researchers were careful to say what their study could not prove.

How big was the study?

The research drew on Phase Three of the International Study of Asthma and Allergies in Childhood (ISAAC), led by Professor Innes Asher's team at the University of Auckland and published in the journal Thorax in January 2013. It covered roughly 319,000 adolescents aged 13 to 14 across 51 countries and about 181,000 children aged 6 to 7 across 31 countries, who answered standardized questionnaires about their diets and symptoms. The full author list and study details are at Food Navigator's coverage of the Thorax paper (doi: 10.1136/thoraxjnl-2012-202285); also covered by ScienceDaily and MedicalDaily.

What did it find? (ScienceDaily's report on the Thorax paper)

• Adolescents eating fast food three or more times a week had a 39% higher risk of severe asthma than those eating it less often; for younger children the increase was 27%.
• The same frequent fast-food pattern was associated with more severe rhinoconjunctivitis (hay fever with itchy, watery eyes) and eczema in both age groups.
• Eating fruit three or more times a week was associated with an 11 to 14% reduction in severe symptoms across all three conditions.

Did the study prove fast food causes asthma?

No, and the researchers said so plainly. This was an observational study: it found an association, not a cause. The authors suggested the higher severity might reflect the high saturated-fat content of fast food affecting the immune system, while fruit's antioxidants might be protective (hypotheses, not findings), and they stressed that more work was needed. Fast food may be a predictor of the severity of symptoms rather than of developing the conditions in the first place (WholeFoods Magazine coverage, ScienceDaily).

What strengthened the finding was its consistency: the association held across countries, genders, and levels of affluence. That consistency adds weight to a possible causal link, but weight is not proof.

What should parents take from this?

The practical message is uncontroversial: a diet heavy in fast food is not doing children's lungs or skin any favors, and fruit appears protective. None of that requires believing fast food single-handedly causes asthma. It is one more reason to keep fast food as an occasional treat rather than a staple.

Ayurveda has long warned that heavy, processed food weakens agni, the digestive fire, and the tradition treats diet as the first medicine. On the digestion side, readers may find Triphala vs isabgol: the two classic bowel remedies compared a useful companion read.

Fast food three times a week, 39% more severe asthma. Association is not proof, but it is not nothing either.

This article is for general information only and is not medical advice. If your child has asthma or eczema, work with your pediatrician on diet and treatment.