That study recorded the frequency of different foods consumed through a parent questionnaire and measured lung capacity in children after exercise, then correlated the two. Those researchers found that the amount of fast-foods consumed corresponded to the degree of asthma as determined by the change in peak flow measurements before and after exercise. The correlation between asthma and foods was true for hamburgers, fried foods (fish and chips), and fizzy drinks (soda). The higher the dose of these foods, the more asthma symptoms occurred. The consumption of other foods was not associated with any outcome, either positive or negative, in relation to lung function. Those other foods included meat, fish, vegetables, fresh fruit, and fruit juice. The authors speculate that the amount of fruit consumed did not show a positive correlation with a reduction in asthma symptoms because the study was conducted in a fruit-growing area where fruit is readily and cheaply available. All of these findings were independent of other factors including childhood obesity and socio-economic factors.

The authors note that several other studies have noted similar associations. For example, fast food was also a risk factor for wheezing among children in Saudi Arabia, and deep-fried food consumption doubled the risk of asthma among teenagers in Taiwan. They also note that other studies have shown that children who consumed fresh fruit five to seven times a week compared with less than once a week had less wheezing, and that Australian children who ate oily fish high in omega-3 fats also had a reduced risk of asthma

Wickens K, et al. Fast foods – are they a risk factor for asthma? Allergy 2005; 60:1537-1541.