High fat food triggers asthma

It's well known that food laden with fat isn't good for your heart, but now a new study suggests that fatty meals may affect lung function, too.

Australian researchers tested people with asthma before and after a high-fat meal or after a low-fat meal, and found that the high-fat meal increased inflammation and reduced lung function.

"This is the first study to look at the effects of a high-fat challenge on airway inflammation. Our preliminary results demonstrate that at four hours after the consumption of the food challenges, subjects who consumed the high-fat meal had an increase in airway inflammation. They also had an impaired response to [asthma medication]," said the study's lead author, Lisa Wood, a lecturer in biomedical sciences and pharmacy at the Hunter Medical Research Institute in New Lambton.

"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," Wood added.

Asthma on the increase

The prevalence of asthma has increased significantly over the past few decades, and one factor that's been implicated in that rise is the typically high-fat Western diet. Dietary fat can activate an immune response and cause inflammation throughout the body, but the specific effects in the airway hadn't been previously studied, according to Wood.

Thirty non-obese people with asthma were recruited for the study, as well as 16 obese adults. The non-obese volunteers were randomly selected to receive either a high-fat or low-fat meal. The obese study participants were all given the high-fat meal.

The high-fat meal consisted of fast-food hamburgers and hash browns. The meal contained about 4 200kj, including 60 grams of fat. That means about 50% of the meal came from fat. A normal meal should contain no more than 25% to 35% of its kilojoules from fat, according to recommendations from the American Heart Association.

The low-fat meal contained a low-fat yogurt. That meal was 840kj and contained 13% fat.

Sputum samples were collected at the start of the study and four hours after the meal. In addition, lung function was tested at both of those times.

What the study revealed

The researchers found that markers of airway inflammation increased significantly among those who ate the high-fat meal. They also found that lung function was affected as well. And people who were given the high-fat meal who then used their asthma inhaler medication saw just a 1% improvement in their lung function. Those on the low-fat meal saw a 4.5% increase in their lung function after using their medication.

"Further work is needed to understand the clinical relevance of these observations. Nonetheless, a difference of 3 to 4% [in lung function] is approaching a level which can be perceived by patients," said Wood.

Wood said the researchers don't know exactly why the body seems to respond to a high-fat meal this way, but said the immune system might be recognising saturated fat as an invading pathogen, which prompts inflammation.

She also said the researchers don't yet know how long these effects might last, but added that if someone is consuming high-fat foods every day, they may be experiencing these effects for at least several hours a day.

Dr. Thomas Leath, division director of allergy and immunology at Scott & White Healthcare in Round Rock, Texas, said, "I wouldn't have thought that the food itself would cause the inflammation. Eating that way can lead to obesity, and fat cells can definitely cause quite a bit of inflammation, but I'm surprised one meal could do this."

Leath said he doubted that the effect on lung function was significant enough for people to notice, but said the study definitely provides "one more reason that people shouldn't eat high-calorie, high-fat diets." - (HealthDay News, May 2010)