Eating three or more weekly servings of fast food is linked to severity of allergic asthma, eczema, and rhinitis in teens (13-14 years old) and children (6-7 years old), according to a large international study published online in the respiratory journal Thorax.
These results - taken from assessments of more than 319,000 teens from 107 centers in 51 countries, and more than 181,000 children from 64 centers in 31 countries - strongly suggest that regular consumption of fast food has major implications for health.
Both teens and the parents of the children were formally quizzed about their weekly diet and whether they had symptoms of wheeze (asthma), a runny or blocked nose accompanied by itchy and watery eyes (rhinoconjunctivitis), or eczema.
They were asked about severity of symptoms over the past 12 months, including frequency and interference with daily life and/or sleep patterns as well as whether they ate foods already linked to protective or damaging effects on health. Food consumption was categorized as never, occasionally, once or twice a week and three or more times a week.
Fast food was the only food type to show the same associations across both age groups with current and severe symptoms of all three conditions seen in teens across all centers, independent of gender or affluence levels. The pattern among the 6-7 year-olds was less clear-cut, which might have to do with the fact that they have fewer food choices.
Specifically, three or more weekly servings were linked to a 39% increased risk of severe asthma among teens and a 27% increased risk among children, as well as to the severity of rhinitis and eczema, overall.
On the other hand, fruit seemed to be protective in both age groups across all centers for all three conditions among children, both current and severe, and for current and severe wheeze and rhinitis among teens.
Eating three or more weekly portions was linked to a reduction in symptom severity of between 11% and 14% among teens and children, respectively.
These findings may be explained by the fact that fast food contains high levels of saturated and trans fatty acids, which are known to affect immunity - while fruit is rich in antioxidants and many other beneficial micronutrients, vitamins and minerals, especially when fresh and locally grown.
These results do not prove cause and effect, but surely deserve further investigation. If the consumption of fast foods leads to symptoms of asthma, rhinoconjunctivitis and eczema, then this study has major implications for public health - not just in the US, but globally.