A plant-based diet can help prevent and manage asthma, while dairy products and high-fat foods raise the risk, according to a new review published in Nutrition Reviews. Researchers with the Physicians Committee for Responsible Medicine examined the evidence related to diet and asthma and found that certain foods—including fruits, vegetables, whole grains, and other high-fiber foods—can be beneficial, while others—such as dairy products and foods high in saturated fat—can be harmful.
"Asthma is a condition that affects more than 25 million Americans, and unfortunately it can make people more vulnerable in the COVID-19 outbreak," says study author Hana Kahleova. "This research offers hope that dietary changes could be helpful."
The review authors highlight a study finding that when compared to a control group, asthma patients who consumed a plant-based diet for eight weeks experienced a greater reduction in use of asthma medication and less severe, less frequent symptoms. In another study, asthma patients adopted a plant-based diet for a year and saw improvements in vital capacity—a measure of the volume of air patients can expel—and other measures.
The authors suggest that a plant-based diet is beneficial because it has been shown to reduce systemic inflammation, which can exacerbate asthma. Plant-based diets are also high in fiber, which has been positively associated with improvements in lung function. The researchers also highlight the antioxidants and flavonoids found in plant foods, which may have a protective effect.
The review also finds that dairy consumption can raise the risk for asthma and worsen symptoms. One 2015 study found that children who consumed the most dairy had higher odds of developing asthma, compared with the children consuming the least. In another study, children with asthma were placed in either a control group, where they made no dietary changes, or in an experimental group where they eliminated dairy and eggs for eight weeks. After eliminating dairy, the experimental group experienced a 22% improvement in peak expiratory flow rate—a measure of how fast the children were able to exhale—while children in the control group experienced a 0.6% decrease.