AMSTERDAM — With new research shedding light on how our food affects respiratory function and the progression of disease, interest in the role of diet in lung health is increasing. The reasoning behind it is based on the possible anti-inflammatory qualities of some diets and the fact that some lung conditions, such as asthma and chronic obstructive pulmonary disease (COPD), are inflammatory diseases, Maria Sfika, MD, pulmonary resident at Attikon University Hospital in Athens, Greece, told Medscape Medical News.

However, at the European Respiratory Society (ERS) 2025 International Congress, in Amsterdam, researchers presented a nuanced picture. While a healthy diet generally supports better lung function and can improve control of certain conditions, its benefits may be mediated through weight control.

Diet’s Role in Disease Progression and Prevention

In a large longitudinal study from the University of Groningen in Netherlands, presented at ERS 2025, researchers followed over 150,000 adults from the Lifelines cohort over time to track changes in their lung function. They found that people with higher dietary quality, which mainly consisted of fruits, vegetables, and whole grains, consistently exhibited superior lung function parameters.

For patients with COPD, a healthier diet was associated with a significantly slower decline in lung function. But while patients with asthma with better diets also had improved lung function at baseline, the study did not observe the same slowing of decline in this group over the follow-up period.

In a separate observational study, also presented at ERS 2025, researchers examined the relationship between plant-based diets and the incidence of asthma symptoms in the large, observational NutriNet-Santé cohort. The study analyzed several dietary patterns, which were scored using different indices, including the Healthful Plant-based Diet Index, the Unhealthful Plant-based Diet Index, and the EAT-Lancet Diet Index (ELDI).

They found that a healthy, plant-based diet, particularly ELDI, was protective against asthma, and the primary mechanism for this benefit was its effect on body weight. Arthur Guets Dombou, MD, PhD candidate at the University of Paris-Saclay, Gif-sur-Yvette, France, explained that the team used a causal mediation analysis to separate the diet’s direct effect on asthma from its indirect effect via BMI. They confirmed an indirect pathway: the diet influences a person’s BMI, which in turn influences their risk for asthma. “By losing weight, [patients] reduce the incidence of asthma symptoms because obesity is a risk factor for asthma,” Guets Dombou told Medscape Medical News.

Diet’s Benefits Have Limits

In a small Greek study published this year in the Journal of Asthma, researchers included patients with all levels of asthma severity to test whether a Mediterranean diet could improve disease control. Although this initial study yielded no statistically significant overall results, researchers observed that patients with severe asthma experienced improved disease control when following the diet.

In a second larger study, presented at ERS 2025, the researchers chose to focus exclusively on patients with severe asthma. They gathered data from 315 adult patients with severe asthma from 16 different lung treatment centers across Greece. They used a validated 14-question survey to assess how closely patients followed a Mediterranean diet, and the standard asthma control test was used to measure disease control. The team also collected data on demographics, medications, and measured patients’ weight and height.

The goal of the analysis was to determine if a better diet score was associated with improved asthma control, Sfika, who presented the study at ERS 2025, said. After accounting for cofounding factors, such as age, BMI, or smoking status, they again found no statistically significant connection between adhering to the Mediterranean diet and having well-controlled asthma. “We only see a trend,” Sfika said. “There is a need for an interventional study to see if we can extract some results.”

However, the study did yield other significant findings that align with those of others regarding weight control. “We found that people with comorbidities such as type 2 diabetes and obesity have worse asthma control symptoms, and this was statistically significant, independent of the diet,” Sfika said.

Beyond the specific link to asthma via weight control, adopting a healthy diet is recommended for a patient’s general well-being, even when the direct effects on a particular lung condition are not statistically significant, Guets Dombou said. In addition, a diet that favors vegetables and limits meat carries implications for planetary health. This environmental co-benefit is particularly relevant to respiratory medicine, he said, as a more sustainable food system could contribute to lower levels of air pollution, thus improving the quality of the air that patients breathe.

Sfika and Guets Dombou reported having no relevant financial relationships.

Manuela Callari is a freelance science journalist specializing in human and planetary health. Her work has been published in The Medical Republic, Rare Disease Advisor, New Scientist, The Guardian, MIT Technology Review, and others.