Background
Asthma prevalence has increased in recent years and evidence suggests that diet may be a contributing factor. Increased use of processed foods has led to a decrease in diet quality, which may be creating a pro-inflammatory environment, thereby leading to the development and/or progression of various chronic inflammatory diseases and conditions. Recently, the Dietary Inflammatory Index (DII) has been developed and validated to assess the inflammatory potential of individual diets.
Objective
This study aimed to examine the DII in subjects with asthma compared to healthy controls and to relate the DII to asthma risk, lung function and systemic inflammation.
Methods
Subjects with asthma (n=99) and healthy controls (n=61) were recruited. Blood was collected and spirometry was performed. The DII was calculated from food frequency questionnaires administered to study subjects.
Results
The mean DII score for the asthmatics was higher than the DII score for healthy controls (−1.40 versus −1.86, p=0.04), indicating their diets were more pro-inflammatory. For every 1 unit increase in DII score the odds of having asthma increased by 70% (OR: 1.70, 95% CI: 1.03, 2.14; p=0.040). FEV1 was significantly associated with DII score (β=−3.44, 95% CI: −6.50,−0.39; p=0.020), indicating that for every 1 unit increase in DII score, FEV1 decreased by 3.44 times. Furthermore, plasma IL-6 concentrations were positively associated with DII score (β=0.13, 95% CI: 0.05, 0.21;p=0.002).
Conclusion and clinical relevance
As assessed using the DII score, the usual diet consumed by asthmatics in this study was pro-inflammatory relative to the diet consumed by the healthy controls. The DII score was associated with increased systemic inflammation and lower lung function. Hence, consumption of pro-inflammatory foods may contribute to worse asthma status and targeting an improvement in DII in asthmatics, as an indicator of suitable dietary intake, might be a useful strategy for improving clinical outcomes in the disease.
Asthma is a chronic respiratory disorder which is associated with airway inflammation. Environmental factors, in association with genetic susceptibility, play a critical role in asthma pathophysiology. Inhaled allergens, smoke exposure, indoor and outdoor air pollution are common triggers of asthma symptoms. Although the role of diet has clearly established mechanisms in diseases such as cardiovascular disease, type 2 diabetes, and cancer, it is not commonly identified as a causal factor in asthma. However, some dietary patterns, such as the Western diet, which includes a high intake of refined grains, processed and red meats, and desserts, have pro-inflammatory effects. On the contrary, the Mediterranean diet, with high intake of fruits and vegetables has anti-inflammatory properties. The influence of food on asthma outcomes is of growing interest, but dietary habits of asthma patients are not commonly investigated in clinical practice. In this review, we focus on the impact of diet on asthma risk and asthma control. We also detail the influence of diet on obese patients with asthma.
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