An analysis of patients at the Children's Hospital of Philadelphia, USA, found that diets high in saturated fat are associated with neutrophilic asthma—one of the most serious and difficult to treat forms—even when patients are not overweight, reports the Daily Mail.

In animal experiments, specialists found that stearic acid – commonly found in animal fats and processed foods – is the cause. This acid triggers a chain reaction in the lungs that leads to inflammation of the airways and ultimately to the development of asthma.

The researchers also found that oleic acid, a fatty acid most commonly found in vegetable oils, especially olive oil, has the opposite effect and can suppress inflammation.

"Prior to this study, many scientists suspected that childhood obesity was the main cause of this type of asthma," said Dr. David Hill, senior researcher and physician at Children's Hospital of Philadelphia. "But we also observed neutrophilic asthma in children who were not obese, which led us to suspect that there might be another mechanism at work. We found in preclinical experiments and in studies with children that diets containing certain long-chain saturated fatty acids can cause neutrophilic asthma regardless of obesity."

More than five million people in the UK suffer from asthma. Around 200,000 of them have a severe form of the disease and usually need to be treated in hospital up to four times a year.

It is estimated that around 15% of patients with severe asthma suffer from neutrophilic asthma, a condition in which the immune system overreacts and fills the lungs with inflammatory white blood cells called neutrophils.

Experts say doctors should advise patients to make changes to their diet to help treat this condition.

"Different subtypes of asthma may require different treatment approaches," says Prof. Lisa Young, a pediatric specialist at the University of Pennsylvania and co-author of the study. "These results are encouraging because they show that targeted dietary changes could help prevent this type of asthma." | BGNES