to the editor: I would like to point out an easy, low-risk preventive therapy that the article on exercise-induced bronchoconstriction did not mention. Ascorbic acid (vitamin C) taken before exercise can be protective against exercise-induced asthma in some persons.^1,2 The effective dose is 1,500 to 2,000 mg one hour before exercise. This therapy does not replace the need to have an albuterol inhaler available.

in reply: Thanks to Dr. Stevenson for mentioning the use of ascorbic acid as a protective agent in the management of exercise-induced asthma. Many different types of therapies have been used, from inhaled heparin to verapamil. I tried to limit this article to therapies with strong evidence-based support.

The studies Dr. Stevenson mentions are intriguing but have several deficiencies. The first deficiency is the number of participants in the study. The Cohen article¹ had only 20 participants, and the Schachter study² had only 12 participants. Another problem is that neither study uses exercise challenge testing protocols, which have been shown to be more sensitive and specific in detecting exercise-induced asthma. Lastly, the Cochrane Collaboration reviewed vitamin C supplementation for the treatment of asthma most recently in 2009.³ Both of these studies were found to have flaws in reporting quality, and the reviewers concluded that the evidence was insufficient to support the use of vitamin C in the management of asthma.

Although many possibly cheaper and simpler treatments may be useful in the management of exercise-induced asthma, physicians should favor evidence-based treatments until these other treatments have stronger evidence to support their use.