Diet and Asthma

Our research team at the Physicians Committee 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.² It is important to continue to work closely with your health care provider to monitor your health and manage your asthma medications, even as you make dietary changes.

Benefits of a Plant-Based Diet

A Mediterranean diet emphasizing plant-based foods has also been associated with improved lung function, improved asthma symptoms such as wheezing, reduced asthma medication use, reduced asthma attack severity, and reduced hospital admissions due to asthma.^3-5 Children born to women who eat a Mediterranean diet during pregnancy have also been found to be at a lower risk of developing asthma symptoms.⁶ A study of Peruvian children found that fruits, vegetables, legumes, and cereals and reduced meat intake lowered the odds of asthma risk.⁷

How does a plant-based diet help? Plant-based diets have been shown to reduce systemic inflammation, which can exacerbate asthma.⁸ Plant-based diets are also high in fiber, which has been positively associated with improvements in lung function.^9-10 Fiber promotes a healthy gut microbiome, which plays a role in immune responses and airway diseases.²

Fruits and Vegetables

Eating fruits and vegetables may be especially beneficial when it comes to asthma. A meta-analysis of more than 40 studies has shown that high consumption of fruits and vegetables is linked to a decreased risk for asthma in children and adults.¹¹ Fruits and vegetables have also been shown to improve lung function and make asthma severity and symptoms, including wheezing, more manageable^.12

Researchers suggest that the antioxidants and flavonoids found in plant foods may have a protective effect, by reducing inflammation in the body and the airways. A study compared a low antioxidant (less than one serving of fruit and two servings of vegetables) to a high antioxidant diet (five servings of vegetables and two servings of fruit per day), and after 14 weeks, those who ate more fruits and vegetables had better lung function and a lower risk of asthma exacerbation, compared to those who ate fewer.¹³

Dangers of Dairy

Studies show that dairy consumption can raise the risk for asthma and worsen symptoms. One study found that children who consumed the most dairy had higher odds of developing asthma, compared with the children consuming the least.¹⁴ 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.¹⁵

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.² Researchers tested the effect of saturated fat by asking participants with asthma to reduce their saturated fat intake for 10 weeks.¹⁶ At the end of the trial, participants experienced reduced airway inflammation. A whole food, pant-based diet is naturally lower in saturated fat, as dairy, meat, eggs, and processed foods are the main sources of saturated fat in the standard American diet.

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 the risk increasing as the degree of obesity increases. A study from California found that children and adolescents who were overweight, moderately obese, or extremely obese had a 16%, 23%, and 37% increased risk of obesity, respectively.¹⁷ In those with asthma, a higher BMI is associated with worse asthma control in children and adolescents and asthma exacerbation in adults.

Research published in 2024 in the Annals of Allergy, Asthma & Immunology suggests that this link between obesity and asthma may be due to many factors, including altered mechanics of breathing secondary to obesity; increased obstructive sleep apnea due to obesity; increased acid reflux due to obesity, which then triggers symptoms of asthma; and increased chronic inflammation resulting from increased adipose tissue.¹⁸ Exercise and diet interventions that result in weight loss can improve asthma symptoms and lung function, and reduce asthma attacks and medication use.¹⁸ Diet changes for children should always be supervised by health care professionals and should focus on building healthy lifestyles rather than solely on weight loss, to discourage unhealthy relationships with food and weight.