Researcher Timothy D. Mickleborough, PhD, and colleagues from the department of kinesiology at the University of Indiana at Bloomington included 20 athletes, equally split between men and women, in their study: 10 were triathletes, five were cross-country runners, and five ran track. Ten of the athletes suffered from exercise-induced asthma and the other 10 didn't; none of the athletes had been diagnosed with asthma caused by other triggers, such as allergies.
Ten of the athletes with exercise-induced asthma were then given daily fish oil supplements for three weeks containing omega-3 polyunsaturated fatty acids -- 3.2 grams of eicosapentaenoic acid and 2.2 grams of docohexanoic acid. As a comparison, the other 10 athletes took capsules containing olive oil. Later the treatments where switched. Neither group knew which capsules they were taking.
To test their lung function researchers told the athletes to exercise to exhaustion on a treadmill.
The results, published in the November issue of American Journal of Respiratory and Critical Care Medicine, are the first to show that fish oil supplements reduce the airway constriction suffered by these elite athletes. Among the athletes with exercise-induced asthma, there was an almost 80% improvement in a lung function test taken 15 minutes after exercise. The athletes also reduced their use of bronchodilators by 20% after exercise.
The researchers suggest the anti-inflammatory properties of fish oil supplements may be the reason for these results.
In an editorial, Jonathan Sadeh, MD, and Elliot Israel, MD, of Harvard Medical School Brigham and Women's Hospital in Boston, call the results "surprising," especially since previous studies using fish oil supplements in people with asthma did not show such a benefit for exercise-induced breathing difficulties.
Sadeh and Israel suggest that exercise-induced asthma may be caused by different reasons in elite athletes than in people with asthma caused by other triggers.
Mickleborough writes that perhaps the only difference may be in the methods used in the individual studies.
Regardless, both groups of researchers feel more studies are warranted.
"Use of a fish oil diet to prevent [exercise-induced asthma] does not appear to be helpful in 'garden variety' asthma, and may still be a little 'fishy' even for elite athletes," Sadeh and Isreal write.
SOURCES: Mickleborough, T. D. American Journal of Respiratory and Critical Care Medicine, November 2003: vol 168: pp 1181-1189. Editorial, Sadeh, J., MD and Israel, E., MD; American Journal of Respiratory and Critical Care Medicine, November 2003; vol 168: pp 1146-1147. News release, American Thoracic Society.