Fats in processed foods can trigger lung inflammation in severe asthma, researchers warn

A new pediatric health paper suggests that improving diets can help treat one type of asthma, after finding that certain lipids (fats) in processed foods can cause lung inflammation. 

Study researchers at the Children’s Hospital of Philadelphia (CHOP), US, noticed that childhood obesity often coincides with neutrophilic asthma, a non-allergic type of asthma triggered by microbial and bacterial proteins.

Neutrophilic asthma is more difficult to treat than allergic asthma. Researchers previously did not understand the underlying causes of this type of asthma, despite it being more likely to be severe enough to send patients to the hospital.

“Prior to this study, many suspected that childhood obesity was causing this form of asthma. However, we were observing neutrophilic asthma in children who weren’t obese, which is why we suspected there might be another mechanism,” explains senior study author David Hill, MD, Ph.D., an attending physician with the Division of Allergy and Immunology at CHOP.

“What we found in both preclinical work and studies in children was that diets containing certain saturated long chain fatty acids can cause neutrophilic asthma independent from obesity.”

Dietary fats shape macrophage activation

The research examined the patterns of lung macrophages, which are white blood cells coordinating immune reactions during inflammation. At the beginning of this research, the authors already knew that metabolic stress can alter macrophage functions, but the impact of diets on this process was unclear.

Certain dietary fats — including those used in processed foods — shape macrophage activation in the lungs during inflammatory responses.The researchers discovered that certain dietary fats — including those used in processed foods — shape macrophage activation in the lungs during inflammatory responses.

A high-fat diet in a preclinical animal model revealed that lung macrophages accumulate a saturated long chain fatty acid called stearic acid, which is often found in animal fat and processed foods.

Notably, dietary stearic acid worsened airway inflammation without causing obesity. Conversely, the “healthy fat” oleic acid, a monounsaturated long chain fatty acid, suppressed inflammatory activity.

Blocking cytokines

The researchers also discovered that blocking inflammatory cytokine IL-1β (messenger proteins) or inhibiting the protein IRE1⍺ protected against stearic acid-driven lung inflammation. Both proteins are found in increased levels in neutrophilic asthma.

The study also confirmed some of these preclinical findings in a group of obese children with asthma.

“Asthma is one of the most common chronic diseases in children, and different treatments may be needed depending on the subtype of asthma,” says study co-author Lisa Young, MD, chief of the Division of Pulmonary and Sleep Medicine at CHOP. 

“While there are many risk factors and triggers that are associated with asthma, this study provides evidence about how specific dietary components are linked to a particularly difficult-to-treat form of asthma.”

Young believes these findings are encouraging because they can inform new treatment strategies, while evidence suggests that modifying diets may help prevent this asthma type.

The findings are published in Science Translational Medicine.