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Diet and Asthma

A plant-based diet can help prevent and manage asthma, while dairy products and high-fat foods raise the risk.

Asthma is a common chronic condition in which the airways become narrow and inflamed—sometimes leading to difficulty with breathing, coughing, wheezing, and shortness of breath. It’s a condition that affects more than 25 million Americans and one that’s on many people’s minds during the COVID-19 outbreak. 

The Centers for Disease Control and Prevention urges those with asthma to have a plan in place—including stocking up on supplies, taking asthma medication as needed, avoiding crowds, and practicing good hygiene. But are there other steps that may be helpful?

Our research team recently 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. We summed up our findings in a new review, which was published in Nutrition in Clinical Care:

Benefits of a Plant-Based Diet

Diets that emphasize fruits, vegetables, grains, and legumes and minimize saturated fat reduce the risk for asthma and may improve asthma control. In one study, 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 compared with those in a control group. 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. Similarly, a study in Peruvian children found that fruits, vegetables, legumes, and cereals and reduced meat intake positively impacted asthma risk.

How does a plant-based diet help? Plant-based diets have 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. Fiber promotes a healthy gut microbiome, which plays a role in immune responses and airway diseases. 

Fruits and Vegetables

Eating fruits and vegetables may be especially beneficial when it comes to asthma. Studies have shown that high consumption of fruits and vegetables is linked to a decreased risk for asthma in children and adults. Fruits and vegetables have also been shown to improve lung function and make asthma symptoms, including wheezing, more manageable. 

Researchers suggest that the antioxidants and flavonoids found in plant foods may have a protective effect.

Dangers of Dairy

Studies show 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.

High-Fat Foods

High fat intake, consumption of saturated fat, and low fiber intake have all been associated with airway inflammation and worsened lung function in asthma patients. Researchers tested the effect of saturated fat—which is found in dairy products, red and processed meats, butter, and certain types of oils—by asking participants with asthma to reduce their saturated fat intake for 10 weeks. At the end of the trial, participants experienced reduced airway inflammation.

Body Weight

Maintaining a healthy body weight can reduce the risk for asthma and help with managing symptoms. Studies have shown that overweight and obese children are at higher risk of developing asthma, with risk increasing as degree of obesity increases. In those with asthma, a higher BMI is associated with worse asthma control in children and adolescents and asthma exacerbation in adults.

Steps To Help Prevent and Manage Asthma