# Diet and Asthma: A Narrative Review
## 4 Diet and Asthma
### Fruits and Vegetables  
Fruits and vegetables are known as a fundamental component of a healthy diet and are recommended to make up half of one's plate at each meal. They offer a variety of nutrients and bioactive compounds that can promote good health and are able to modulate inflammation and prevent chronic diseases [47]. In asthmatic children, fruit and vegetable intake was found to be negatively associated in nasal lavage with IL-8, a marker of inflammation [54]. A study suggested an inverse significant relationship between salad consumption (a source of antioxidants) and FeNO, in children [55]. It was also observed that a greater daily vegetable diversity intake was negatively associated with having self-reported asthma with an odds ratio (OR) = 0.67; 95% CI 0.47, 0.95, whereas a vegetable diversity ingestion superior to three items per day was negatively associated with levels of FeNO \(\geq\) 35 ppb (OR = 0.38; 95% CI 0.16, 0.88) and breathing difficulties (OR = 0.39; 95% CI 0.16, 0.97) in school-aged children [56]. A longitudinal study on children up to 5 years observed that the risk of asthma was not associated with the consumption of all fruits and vegetables together, but inverse associations were seen between all leafy vegetables and asthma (Hazard Ratio (HR) = 0.87, 95% CI 0.77; 0.99), and unprocessed vegetables and non-atopic asthma (HR = 0.90, 95% CI 0.81; 0.98), respectively [57]. A cohort study demonstrated that a higher fruit intake at 8 years of age was associated with a tendency to lower the odds of prevalent asthma (T3 vs. T1, OR 0.78; 95% CI 0.60-1.01, \(p\)-trend 0.083), with reduced odds of incident asthma, and increased odds of remittent asthma (OR = 0.76; 95% CI 0.58-0.99 and OR = 1.60; 95% CI 1.05-2.42, respectively) for up to 24 years [58]. Another study conducted in adults revealed that reducing the intake of antioxidant foods worsens asthma control and lung function. Furthermore, it was demonstrated that an increase in airway neutrophils, resulting from a low-antioxidant diet, can be reversed using lycopene-rich treatments (such as tomato juice) that lead to a decrease in airway neutrophil influx [59]. [PERSON] et al. [60] compared the outcomes of a high-antioxidant diet to those of a low-antioxidant diet, with and without lycopene supplementation, in asthmatic patients, over the course of a 16-week period. It was observed that participants on the high fruit and vegetable intervention arm (high-antioxidant diet) had fewer asthma exacerbations. Several participants in the low fruit and vegetable arm (low-antioxidant diet) were given an antioxidant supplement, but this did not reduce the risk of asthma exacerbations. As improvements were only observed after increasing fruit and vegetable consumption, whole-food interventions seem to be more effective, implying that the whole food dietary component is more relevant than antioxidant supplementation [60]. Two meta-analyzes found that a higher intake of fruit and vegetables was associated with a lower risk of having asthma [61; 62]. One of the meta-analyzes found that vegetable intake was negatively associated with the risk of prevalent asthma (OR = 0.95; 95% CI0.92; 0.98) and that fruit intake was negatively associated with the risk of prevalent wheeze (OR = 0.94; 95% CI 0.91; 0.97) and asthma severity (OR = 0.61; 95% CI 0.44; 0.87) [62]. Six of the seven studies found that fruit and vegetable intake in asthmatics had a protective effect against either airway or systemic inflammation [62]. The other meta-analysis also found protective effects of the total intake of vegetables and fruits in asthmatic children with a relative risk (RR) of 0.57 (95% CI 0.42; 0.77). Fruit consumption was found to reduce the risk of wheeze and asthma (RR = 0.81, 95% CI 0.74; 0.88, and RR = 0.90, 95% CI 0.86; 0.94, respectively). Similarly, the intake of vegetables reduced the risk of wheeze and asthma (RR = 0.88, 95% CI 0.79; 0.97, and RR = 0.91, 95% CI 0.82; 1.00, respectively) [61].