Fast food tied to greater risk of asthma and other allergies
Fast food consumption, in particular hamburger, was associated with an increased risk of asthma and wheeze in a dose-dependent manner, suggests a meta-analysis of 16 trials.
Based on study design and outcomes, adjusted odds ratios (aORs) were pooled from six cross-sectional and three case-control studies for the primary outcome of asthma and wheeze. Fast food consumption was significantly associated with an increased risk of current asthma (aOR, 1.58), ever asthma (aOR, 1.36), and severe asthma (aOR, 1.34). [Respirology 2018;doi:10.1111/resp.13339]
Similarly, intake of fast food was associated with a greater risk of current wheeze (aOR, 1.21) and ever having wheeze (aOR, 1.65) in the pooled cross-sectional studies.
However, sensitivity analyses on studies which adjusted for BMI showed that the associations between fast food consumption and current asthma, ever asthma, or current wheeze were nullified, which indicates BMI as a potential confounder.
Nonetheless, fast food intake remained associated with current asthma when only case-control studies were included (aOR, 1.58) and with ever having wheeze (aOR, 1.65) in the sensitivity analyses.
“Fast food consumption is associated with poor diet quality, high caloric intake, overweight, and obesity in children and adolescents,” according to the researchers, who noted that “overweight–obesity is an independent risk for asthma and allergic sensitization.”
Compared with individuals who consumed fast food 1–2 times per week, those who had fast food ≥3 times a week had an increased risk of severe asthma (aORs, 1.09 vs 1.34; p<0.001) as well as current wheeze (aORs, 1.07 vs 1.22; p<0.001).
In particular, consuming hamburgers ≥3 times a week was associated with an elevated risk of severe asthma (aORs, 1.34 vs 1.09; p<0.001) and current wheeze (aORs, 1.22 vs 1.07; p<0.001) compared with hamburger consumption of 1–2 times per week.
Conversely, no association was found between carbonated soft drinks and risk of asthma or wheeze.
In addition, fast food consumption was associated with physician-diagnosed allergic rhinitis (OR, 1.43), severe eczema (aOR, 1.51), and severe rhino-conjunctivitis (aOR, 1.54).
The researchers believed that a poor-quality diet may be one of the underlying mechanisms mediating the association between fast food and risk of asthma or wheeze. For instance, saturated fatty acids from fast food can induce release of pro-inflammatory cytokines, which can contribute to chronic inflammation of the airways. Also, “substitution effect” may play a role — consuming fast food reduces the intake of fruits and vegetables which may protect against asthma development.
As the studies included in the meta-analysis were based on self-reported data, which were subjected to recall bias, the researchers acknowledged this may limit the strength of the findings. Also, heterogeneity in the design of the studies might introduce residual confounding.
“Additional studies are needed to confirm the relationships seen in this analysis, however, and to identify potential causal associations between the consumption of fast food and allergic diseases,” said study principal investigator Dr Wang Gang of West China Hospital, Sichuan University in Chengdu, China.
“[These associations] could in some degree explain the increasing prevalence of these diseases and offer a potential intervention strategy,” he added.