Written by Greg Arnold, DC, CSCS. Vitamin C “significantly reduced” the maximum fall in post-exercise forced expelled volume of air (up to 56%) compared to the placebo group. Urinary levels of the inflammatory proteins were also “significantly lower” (up to 62%) in the vitamin C group compared to placebo.
Asthma is the third-ranking cause of hospitalization among those younger than 15 years of age, costing $3.2 billion and 14 million lost school days each year. (1) It affects more than 20 million Americans, including 6.1 million children. (2)
A new area of interest in the onset of exercise-induced asthma is the role antioxidants play in the condition. With new research (3) reinforcing how low dietary intake of fruit and antioxidants “may be a potentially modifiable risk factor for the development of asthma”, a new study (4) has continued to focus more specifically on vitamin C, the most intensively studied antioxidant for exercise-induced asthma. (5)
In the study, eight patients with asthma were given either 1500 mg per day of vitamin C or placebo for two weeks. The patients then had neither for one week (the “washout” period) and then switched treatments. During both treatment periods researchers measured lung function of the patients that included forced expiratory volume (FEV), measured urine levels of inflammatory proteins, and completed a 12 items Asthma Quality of Life Questionnaire (AQLQ) to subjectively report their symptoms.
The researchers also conducted “exercise challenge testing” on the patients where they ran on a motorized treadmill elevated 1% per minute until 85% of their maximum heart rate and breathing rate were reached and then maintained this exercise intensity for 6 minutes (6). Following the 6-minute exercise period, the grade of the treadmill continued to increase at 1% per minute until the patients reached exhaustion.
In both treatment periods, vitamin C “significantly reduced” the maximum fall in post-exercise FEV (up to 56%) compared to the placebo group. Urinary levels of the inflammatory proteins were also “significantly lower” (up to 62%) in the vitamin C group compared to placebo. Finally, AQLQ scores “significantly improved” in the vitamin C group compared to placebo.
Although this was a small study of only eight patients, the researchers concluded that “This double-blind, randomized, crossover, placebo-controlled study has demonstrated that 1500 mg/d of [vitamin C] supplementation for 2 weeks attenuates the bronchoconstrictive response to exercise in asthmatic subjects.”
Source: Tecklenburg, Sandra L., Timothy D. Mickleborough, Alyce D. Fly, Yeon Bai, and Joel M. Stager. “Ascorbic acid supplementation attenuates exercise-induced bronchoconstriction in patients with asthma.” Respiratory medicine 101, no. 8 (2007): 1770-1778.
© 2007 Elsevier Ltd. All rights reserved.
Posted December 11, 2008.
References:
- CDC’s National Center for Environmental Health Website. “Asthma’s Impact on Children and Adolescents”.
- “Asthma” posted on the American Lung Association Website.
- Patel BD. Dietary antioxidants and asthma in adults. Thorax, May 2006; 61; 388 – 393.
- Tecklenburg SL. Ascorbic acid supplementation attenuates exercise-induced bronchoconstriction in patients with asthma Respiratory Medicine (2007) 101, 1770–1778.
- Christofidou-Solomidou M, Muzykantov VR. Antioxidant strategies in respiratory medicine. Treat Respir Med 2006;5: 47–78.
- American Thoracic Society Guidelines for Methacholine and Exercise Challenge Testing 1999, Am J Respir Crit Care Med 2000;161:309-29.
