Last modified: Monday, January 9, 2006
Fish oil shown to reduce airway inflammation caused by exercise-induced asthma
BLOOMINGTON, Ind. -- People suffering from exercise-induced asthma were able to reduce their symptoms below the threshold used to diagnose the disease by eating a diet supplemented with fish oil, according to new research findings from Indiana University reported in the January issue of the journal Chest.
The special diet reduced narrowing of the patient's airway and enabled the person to use less asthma medication, the study showed. These and related research findings by exercise physiologist Timothy D. Mickleborough offer the prospect of combining dietary supplementation with reduced medication in a treatment that could be at least as beneficial as either in isolation. There would also be fewer of the potential side effects from medication, such as reduced effectiveness from long-term use and toxicity from some medications.
"There have been remarkable advances in asthma therapy over the last 10 years. Inhaled corticosteroids and short-acting beta-2-agonists have proven to be highly effective. Long-acting beta-2-agonists have facilitated the control of asthma, and daily medications such as leukotriene modifiers have recently proven highly effective in asthma therapy. However, these medications are not without real and potential side effects," said Mickleborough, assistant professor in the Department of Kinesiology at IU Bloomington. "Alternative therapies for EIA, or therapies that reduce the dose requirements of traditional medications, would be of benefit to the asthmatic and potentially reduce the public health burden of this disease."
In exercise-induced asthma, vigorous exercise triggers an acute narrowing of the airway afterward, making breathing difficult. Around 80 percent of people with asthma have this condition, also called exercise-induced bronchoconstriction. EIA also is found in an estimated 10 percent or more of elite athletes and as much as 10 percent of the general population without asthma.
EIA can discourage people, particularly children, from participating in sports and other physical activity.
"Exercise is a powerful trigger for asthma symptoms, so young individuals may avoid vigorous activity, resulting in damaging consequences to their physical and social well-being," Mickleborough said.
In the study, the post-exercise lung function of participants -- adults with mild-to-moderate persistent asthma -- improved by about 64 percent and their use of emergency inhalers decreased by 31 percent when they consumed a diet supplemented with fish oil, rich in omega-3 polyunsaturated fatty acids (n-3 PUFA), for three weeks.
The typical diet in Western societies includes 20 to 25 times more n-6 polyunsaturated fatty acids than n-3 PUFA and is considered pro-inflammatory. N-6 PUFA are found in such items as sunflower, safflower and corn oils. N-3 PUFA also are found in canola and flaxseed oils.
One of the key findings from the study was that, while on the diet supplemented with fish oil -- 3.2 grams of eicosapentaenoic acid (EPA) and 2 grams of docohexaenoic acid (DHA) daily -- airway pro-inflammatory cells and markers, which are responsible for airway inflammation and subsequent airway obstruction, were reduced in sputum taken from the EIA subjects.
The randomized, double-blind cross-over study involved 16 people with mild-to-moderate persistent asthma, meaning they required daily maintenance medications to control their symptoms. The study participants did not use their maintenance medication during the course of the study. They were all considered recreationally active. The fish oil was pharmaceutical grade, meaning it was purified at a molecular level to remove metals and other harmful contaminants that can be present in fish oil products sold in retail stores, including health food stores. No standards exist for the pharmaceutical-grade label, so the quality of fish oil labeled as such varies.
Co-authors of the report include Martin Lindley, research scientist in the IUB Department of Kinesiology; Alyce Fly, associate professor in the IUB Department of Applied Health Science; and Alina Ionescu, Department of Respiratory Medicine, University of Wales College of Medicine, Cardiff, UK.
Studies on the impact of diet on EIA are scant and inconclusive. Research by Mickleborough and his colleagues has provided the most complete picture to date of the impact fish oil and low-salt diets (see https://newsinfo.iu.edu/news/page/normal/2175.html) can have on EIA.
Mickleborough can be reached at 812-855-0753 and tmickleb@indiana.edu.
