Background: Overweight and obesity is prevalent in adults with asthma and associated with neutrophilic airway inflammation and oxidative stress. The effect of dietary carotenoids in overweight/obese adults with asthma is unknown.
Aims: (1) To compare airway neutrophil markers, systemic inflammation and carotenoid levels in healthy-weight versus overweight/obese adults with asthma. (2) To examine the effects of a high, versus low, fruit and vegetable diet on these markers in overweight/obese asthmatic adults.
Methods: In a cross-sectional analysis, sputum neutrophil elastase activity, toll-like receptor (TLR)-4 gene expression and IL8 levels, plasma carotenoids and systemic inflammation were compared between healthy-weight (BMI <25kg/m2) and overweight/obese (BMI ≥25kg/m2) adults with asthma. Changes in these biomarkers were then compared between overweight/obese asthmatic adults randomised to a high (HFV) versus low (LFV) fruit and vegetable diet for 14 weeks.
Results: Baseline sputum neutrophil elastase, TLR4 expression and IL8 were higher in the overweight/obese (n=106) versus the healthy-weight (n=27) adults; conversely, plasma carotenoids were reduced. Following the 14-week RCT, neutrophil elastase decreased in the HFV (n=33) versus LFV (n=63) group (-28.5 (-350.4, 64.6) vs. 211.5 (-15.4, 1508.7) ng/mL, p=0.045), as did CRP (-0.2 (-2.8, 0.8) vs. 0.8 (0.1, 4.9) mg/L, p=0.014). Lutein and alpha-carotene increased in the HFV versus LFV group.
Conclusion: Markers of airway neutrophils were raised in overweight/obese adults with asthma; however, neutrophil activity reduced following a 14-week high fruit and vegetable diet, while circulating carotenoids increased. Dietary intervention may be beneficial in obese adults with asthma.
Funding source: NHMRC