Caffeine, lung function, and asthma:
Caffeine doses for asthma:
Caffeine at a dose of 7 mg/kg was reported to improve lung function in a study that included 10 individuals with bronchial asthma. Patients were given placebo and caffeine (3.5 mg/kg and 7 mg/kg ) two hours prior to exercise and a lung function test (spirometry) was administered an hour and two hours after and at 5, 15, and 30 minutes post exercise. Forced expiratory volume (FEV1), a measure of lung function, improved significantly and stopped constriction of the airways in the lungs caused by exercise. (17)
Caffeine and pulmonary function testing:
A review examined seven available clinical trials on caffeine in asthma, specifically on caffeine’s effect on lung function tests. Of the 55 asthmatics in these studies, some were given caffeine and others were given placebos. The results showed that even small amounts of caffeine (< 5mg/kg body weight) helps asthmatics breathe more easily for 2 to 4 hours after ingestion. Forced expiratory volume (FEV1), a measure of lung function, showed a small mean improvement of 5% up to 2 hours after consumption of caffeine. In 2 separate studies mean FEV1 improvement were reported at 12% and 18% after caffeine. Another clinical trial looked at the effect of caffeine on exhaled nitric oxide levels and found that there is no significant effect. (18)