They recruited 40 people with asthma. Some received a high-fat, high-calorie meal of fast food hamburgers and hash browns containing about 1,000 calories, 52% of which was fat; others ate a low-fat, low-calorie meal of reduced fat yogurt, containing about 200 calories and 13% fat.
The scientists collected sputum samples before patients ate and again four hours later, and analyzed the samples for inflammatory markers.
People who had eaten the high-fat meal had reduced response to the bronchodilators, compared to people who had eaten fewer calories and less fat.
“This is the first study to show that a high-fat meal increases airway inflammation, so this is a very important finding,” says study author Leslie Wood, PhD, a research fellow at the University of Newcastle in Australia. “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.”
The people who ate the high-fat meal had an increase in airway neutrophils, the most common type of white blood cell and one of the first to arrive at an infection site, the researchers say. They also had a marked increase in activity of a cell surface receptor called TLR4 that is activated by fatty acids.
According to the researchers, TLR4 senses the presence of saturated fatty acids, causing cells to respond as if they have been invaded by a pathogen and leading to a release of inflammatory mediators. This increase in the activity of TLR4 suggests that dietary fat is a cause of inflammation.
Woods says in a news release that evidence suggesting that a high-fat meal changes the asthmatic response to albuterol was unexpected and needs more study.
“We also are investigating whether drugs that modify fat metabolism could suppress the negative effects of a high fat-meal in the airways,” Woods says. “If these results can be confirmed by further research, this suggests that strategies aimed at reducing dietary fat intake may be useful in managing asthma.”
Prevalence of asthma has increased dramatically in western countries in recent decades, suggesting that an environmental factor, such as food consumption, could trigger or aggravate an asthma attack.