Background – An antioxidant-rich diet has been associated with reduced asthma prevalence in epidemiological studies. However, there has been no direct evidence that altering the intake of antioxidant-rich foods affects asthma outcomes.
Objectives – This study aimed to investigate changes in asthma control and airway inflammation resulting from a low antioxidant diet and subsequent use of lycopene-rich supplements.
Design – Adults with stable asthma (n=32) consumed a low antioxidant diet for 10 days, then commenced a placebo controlled, randomized, cross-over trial using lycopene-rich supplements. 17 subjects completed the trial in which they received 3 x 7 day treatment arms (placebo, lycopene concentrate and tomato juice), each separated by a 10 day washout. The tomato juice and lycopene concentrate each provided 45mg/day lycopene. Clinical status was monitored using spirometry and the Asthma Control Score questionnaire. Airway inflammation was assessed using total and differential cell counts from induced sputum. Plasma carotenoids and tocopherols, were measured by HPLC.
Outcomes – Following the initial washout period on the low antioxidant diet, plasma carotenoid concentrations decreased (p=0.026) and asthma control worsened, including increased Asthma Control Score (0.035) and decreased %FEV1 (0.004) and %FVC (0.002). Furthermore, airway inflammation worsened, with increased %neutrophils in induced sputum (p=0.038). Supplementation with both tomato juice and lycopene concentrate reduced neutrophilic airway inflammation (placebo: 55.1 (35.0, 91.1) % versus tomato juice: 42.0 (21.0, 67.8) % versus lycopene concentrate: 39.8 (18.4, 77.5) %; (p=0.006).
Conclusion – A low antioxidant diet worsens asthma control, lung function and noneosinophilic airway inflammation. Lycopene-rich supplements reverse this trend in airway inflammation. Dietary antioxidant consumption is an important variable that modifies clinical asthma status, and changes in dietary antioxidant intake may be relevant to the rising asthma prevalence and as a therapeutic intervention.