Blocking effect of vitamin C in exercise-induced asthma
H. A. Cohen, I. Neuman and H. Nahum
Pediatric Ambulatory Clinic, Rabin Medical Center, Petach Tiqva, Israel.
OBJECTIVE: To determine if vitamin C (ascorbic acid) has a protective
effect on the hyperreactive airways of patients with exercise-induced
asthma (EIA). DESIGN: All the patients underwent pulmonary function tests
at rest, before and 1 hour after receiving 2 g of oral ascorbic acid. They
were then randomly assigned in a double-blind manner to receive 2 g of
ascorbic acid or a placebo 1 hour before a 7-minute exercise session on a
treadmill. Pulmonary function tests were performed after an 8-minute rest.
This procedure was repeated 1 week later, with each patient receiving the
alternative medication. SETTING: A university hospital. PARTICIPANTS:
Twenty patients with asthma (13 males and 7 females), with ages ranging
from 7 to 28 years (mean, 13.8 years). All patients who had a decline of at
least 15% in their forced expiratory volume in 1 second after a standard
exercise test on a motorized treadmill received a diagnosis of EIA.
MAIN-OUTCOME MEASURES: All patients were advised to stop using their
regular asthma medication or bronchodilator 12 hours before the test.
Pulmonary function tests were performed in the same ambient conditions on
all patients. RESULTS: All patients received a diagnosis of EIA. Ascorbic
acid administration did not change the results of pulmonary functions at
rest after 1 hour. In 9 patients, a protective effect on exercise-induced
hyperreactive airways was documented. Four of 5 patients who received
ascorbic acid and documented a protective effect on EIA continued to
receive ascorbic acid, 0.5 g/d, for 2 more weeks with the same protective
effect. CONCLUSIONS: The efficacy of vitamin C in preventing EIA cannot be
predicted. However, vitamin C may have a protective effect on airway
hyperreactivity in some patients with EIA.
