A new study has suggested that eating fatty, processed foods could be a key factor in triggering a severe form of asthma

Asthma affects more than five million people in the UK, with symptoms being triggered by common everyday activities like exercise, changes in the weather, and allergens. Around 200,000 people in the UK are classed as having severe asthma, with harder-to-control symptoms and higher doses of medicine needed. While most people can keep their asthma under control with medication, those with more severe asthma can experience asthma attacks.

Researchers at the Children’s Hospital of Philadelphia have pinpointed a new cause that can lead to asthma. According to the researchers, some lipids (fats) found in processed foods can cause inflammation in people’s airways, which can, in turn, trigger severe asthma. An analysis of patients found that diets high in saturated fats were associated with neutrophilic asthma – a severe form of asthma which often leads to corticosteroid resistance and poor control of symptoms. 

More difficult to treat than the more common allergic asthma, neutrophilic asthma is typically triggered by microbial and bacterial proteins. Researchers noticed a link between childhood obesity and neutrophilic asthma. The study aimed to find out if this connection may cause neutrophilic asthma.

Researchers found that some dietary fats (such as those used in processed foods) can influence how immune cells in the lungs (macrophages) react when there is inflammation. Essentially, what we eat can negatively impact our lungs’ immune defences, affecting how our bodies fight irritation or infection. Prior to this study, many researchers suspected that childhood obesity was causing this particular form of asthma. However, neutrophilic asthma is still seen in children who aren’t obese. 

Senior study author David A. Hill, MD, PhD, and attending physician within the Division of Allergy and Immunology at Children’s Hospital of Philadelphia, said, “We found in both preclinical work and studies in children that diets containing certain saturated long chain fatty acids can cause neutrophilic asthma independent from obesity.” 

In animal studies, researchers discovered stearic acid (often found in animal fat and processed foods) was the cause, starting a chain reaction in the lungs which causes inflammation in the airways, resulting in asthma. The study also revealed that oleic acid (found in vegetable oils) has the opposite effect and can suppress inflammation. 

Thanks to these new findings, experts are suggesting that doctors should advise patients to make dietary changes to help them manage their condition. Study co-author, Professor Lisa Young, a paediatric specialist at the University of Pennsylvania, says, “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. These findings are encouraging because they provide new treatment strategies and suggest that targeted dietary modifications may help prevent this asthma type.”

A previous study into the role of nutrition in asthma prevention and treatment suggested increasing the amount of fruit and vegetables eaten daily, as well as decreasing how much saturated fat and dairy eaten. Mediterranean and vegan diets emphasising fruits, vegetables, grains and legumes and reducing or removing animal products were suggested as potentially helping reduce asthma risk and helping with better asthma control. 

A Mediterranean diet can offer numerous benefits. Anti-inflammatory and nutrient-dense, it also promotes gut health and avoids processed and refined foods that can often be high in sugar and hydrogenated fats. The NHS also recommends optimising your diet to help with asthma, as this can help alleviate symptoms. Eating healthily and including more fruit, vegetables, nuts, lean meat, fish, and seafood can help. Ensuring you have enough fibre and antioxidants such as vitamin E and C can help reduce inflammation in your airways. 

An increasing body of research into the effects of processed foods and ultra-processed foods (UPFs) and how they may cause a surge in ill health is emerging. Processed foods have been linked to increased risk of heart disease, obesity, stroke, some cancers, depression and anxiety. Yet despite the risks, ultra-processed foods account for a significant part of our diets. Nutritional therapist Mivai Pili explains more.

"Ultra-processed foods account for about 56% of daily energy intake for adults. The high intake of these nutrient-poor foods is linked to numerous health issues. The solution to mitigating these dangers lies in reducing the intake of ultra-processed foods and embracing a diet rich in whole, minimally processed foods. Whole foods — such as fruits, vegetables, nuts, seeds, whole grains, and legumes — are nutrient-dense and provide the essential vitamins and minerals needed for optimal brain function. By prioritising these foods, you can naturally decrease inflammation and improve overall health."

These findings mark an exciting step in understanding how what we eat influences asthma. With greater awareness, better food choices, and continued scientific progress, people with asthma may soon have more ways than ever to take control of their health and breathe a little easier.