Which food has been shown to directly affect airway narrowing and inflammation in asthma?

Caffeine has been shown to have a direct impact on airway narrowing and inflammation in asthma due to its bronchodilator effects. It is a methylxanthine, similar in structure to theophylline, which is a medication used to treat asthma. Caffeine can help relax the muscles around the airways, leading to dilation and improved airflow. Additionally, it may reduce inflammation in the airways, providing some relief from asthma symptoms.

In contrast, other food options listed do not have the same level of evidence supporting their effects on asthma. For example, chocolate and dairy products can sometimes lead to increased mucus production in some individuals, which may aggravate asthma symptoms in sensitive individuals. Spicy foods may provoke reflux in some people, potentially triggering asthma symptoms, but they do not possess the same direct bronchodilator properties as caffeine. This distinction helps clarify why caffeine stands out as the correct answer in the context of asthma management.