The spread of poor diets with large amounts of processed food, fat and refined sugar could be leading to increasing levels of inflammation in the body and, as a result, contributing to increased asthma prevalence, say researchers.
The researchers looked at the Dietary Inflammatory Index (DII) in people with asthma compared with healthy controls to relate the index to the risk of asthma, lung function and systemic inflammation.
Ninety nine people with stable asthma and 61 healthy controls were studied. Lung function was tested through blood tests and spirometry, and the DII was worked out from questionnaires on food frequency of the subjects.
“Consumption of pro-inﬂammatory foods in the diet may contribute to worse asthma status”
The mean index score for people with asthma was found to be greater than that for healthy controls. The indication was that diets of people with asthma were more pro-inflammatory than those of controls and for each unit increase in index score there was a 62% rise in the chance of having asthma.
Lung function was also found to have a significant link with the index score, with a lowering of roughly 10% in the third of patients with the highest index score, compared with the third of patients with the lowest.
A further inflammation indicator − levels of inflammatory marker interleukin-6 in the blood − was positively linked with index score.
The index score was linked to lower lung function and greater systemic inflammation, said Lisa Wood, head of the Nutrition programme at the Centre for Asthma and Respiratory Diseases, University of Newcastle in New South Wales.
“The usual diet consumed by asthmatics in this study was pro-inﬂammatory relative to the diet consumed by the healthy controls, as assessed using the DII score,” she said.
“The DII score was associated with lower lung function and increased systemic inﬂammation,” she said. “Hence, consumption of pro-inﬂammatory foods in the diet may contribute to worse asthma status.”
The researchers are now designing more studies to look at how dietary components reduce inflammation and clinical asthma outcomes, for example dietary fibre and antioxidants.
The index was developed in 2009 at the University of South Carolina, and it was validated to assess individual diets’ inflammatory potential.
- The study was presented at the meeting of the Thoracic Society of Australia and New Zealand (see PDF containing conference abstracts, above right)