RCT to determine whether increased fruit and vegetable intake reduces asthma symptoms and microbiology in children with asthma

Background: Fruit and vegetables contain many anti-inflammatory and antioxidant nutrients which may be protective in asthma, with evidence showing increased intake is inversely associated with wheeze and asthma risk, and positively associated with lung function. This study aimed to examine the effect of a high fruit and vegetable diet in children with asthma and the potential anti-inflammatory mechanisms involved. Methods: Children aged 3-11 years with asthma (n=47) were randomised to a high (n=22) or low (n=25) fruit and vegetable diet for 6 months, with fortnightly dietetic counselling. At baseline, 3 months and 6 months fasting blood samples were collected, lung function was measured by impulse oscillometry, and lung clearance index was measured using nitrogen multiple breath washout. Plasma carotenoids were analysed with high performance liquid chromatography, systemic inflammation (plasma high-sensitivity TNF-a, CRP, and IL-6) was measured by ELISA. Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood using Ficoll density gradient, and RNA and nuclear proteins were extracted and quantified. Gene expression was measured by qPCR, and HDAC enzyme activity was measured using fluorescent assays. Faecal microbiota were analysed.Results: After 6 months, improvements in lung function, as indicated by a decrease in airway resistance (R5-R20, p=0.04) and improvement in airway reactance (X5 p=0.038 and Ax p=0.001) were observed in the high F&V group. In the low F&V group, systemic inflammation (hsCRP) significantly increased (? 0.37 [-0.04, 1.58], p=0.04), with a decrease in GRP41 gene expression (? -0.17 [-3.64, 0.47], p=0.01), and an increase in HDAC enzyme activity observed after 6 months (? 0.80 [-0.26, 1.71], p<0.01). Change in F&V consumption was found to be inversely associated with change in hsCRP (Rs= -0.32, p=0.037) and HDAC enzyme activity (Rs=-0.36, p=0.018), with change in HDAC activity positively correlated with change in hsCRP (Rs=0.37, p=0.016)Conclusion: This study provides promising evidence for the beneficial effects of increasing fruit and vegetable intake in children with asthma, with significant improvements in lung function observed. Furthermore, these observations suggest that a high F&V diet may be protective against an increase in systemic inflammation in children with asthma. Additional research is needed to confirm the effects of a higher fruit and vegetable diet on clinical findings, and to provide further evidence for the anti-inflammatory mechanisms of fruit and vegetables, in particular the effect on HDAC activity.