Although yet to be confirmed with further studies, new research from Australia suggests eating high fat high energy meals may not be advisable for people with asthma because they can lead to airway inflammation and may also suppress the benefit of the asthma reliever medication Ventolin (albuterol).

These are the findings of a study to be presented this week at the American Thoracic Society ATS 2010 International Conference in New Orleans that is taking place from May 14th to 19th.

Dr. Lisa Wood, a research fellow of the University of Newcastle, New South Wales, and colleagues monitored asthma patients after they ate low and high fat meals and found that within hours of eating the high fat meal they were showing signs of airway inflammation not seen when they ate the low fat meal, and the high fat meal also appeared to inhibit their response to the asthma reliever Ventolin (albuterol).

“Subjects who had consumed the high-fat meal had an increase in airway neutrophils and TLR4 mRNA gene expression from sputum cells, that didn’t occur following the low fat meal,” said Wood in a media statement.

“The high fat meal impaired the asthmatic response to albuterol. In subjects who had consumed a high fat meal, the post-albuterol improvement in lung function at three and four hours was suppressed,” she added.

Rates of asthma have gone up in westernized countries in recent decades, and experts suggest environmental factors like lifestyle and diet may be an important factor, especially since westernized diets have considerably more fat than more traditional ones.

Previous research shows that high fat diets stimulate the immune system, causing higher levels of inflammation markers in the blood. However, the researchers believe this is the first study to examine how a high fat meal may affect airway inflammation.

For the study, Wood and colleagues recruited 40 people with asthma and randomly assigned them to one of two groups: the high fat, high calorie meal group or the low fat, low calorie meal group.

The high fat, high calorie meal of fast food burgers and hash browns contained about 1,000 calories, with over 50 per cent of them coming from fat.

The low fat, low calorie meal of reduced fat yogurt contained about 200 calories, with only 13 per cent of them from fat.

The researchers took sputum samples from the participants before and four hours after the meal and tested them for markers of inflammation. (Sputum contains mucus from the lungs).

The results showed that:

  • Sputum of participants who had consumed the high fat high energy meal showed a marked increase in airway neutrophils and TLR4 mRNA gene expression.
  • Participants who ate the high fat high energy meal also had reduced reduced bronchodilator response compared to those who had the low fat, low energy meal (assessed by FEV1% predicted and FEV1/FVC%).

One potential criticism of the study is that it did not differentiate between high fat and high energy, but because of the TLR4 response, the authors said it suggests it is the fat rather than the high energy that produced the inflammatory response.

TLR4 (toll-like receptor 4) is a receptor that sits on the surface of cells and triggers an inflammatory response when it senses nutritional fatty acids, instructing the cell to treat them like invading pathogens.

Wood said the study was important because it was the first to show a high fat meal can produce this effect.

She also said the observation that:

“A high fat meal changes the asthmatic response to albuterol was unexpected as we hadn’t considered the possibility that this would occur.”

The researchers said further studies should explore the biology of how a high fat meal could alter the response to a bronchodilator. Wood said they are already starting to look at this and also:

“Whether drugs that modify fat metabolism could suppress the negative effects of a high fat meal in the airways.”

If further studies confirm these findings, then perhaps we should be considering advising people with asthma to reduce fat in their diets, they said.

“A High Fat Challenge Enhances Innate Immune Responses in Asthmatic Airways.”
L Wood, et al
Abstract 2474, Session C103, Tuesday, May 18, ATS 2010 International Conference.

Source: American Thoracic Society.

Written by: Catharine Paddock, PhD