Asthma and vitamin C.

OBJECTIVE: To define what role vitamin C may or may not play in the treatment of asthma. DATA SOURCES: A comprehensive literature search of relevant English-language papers identified through a Medline search and from bibliographies of the identified papers. STUDY SELECTION: We identified papers and studies pertaining to vitamin C in asthma and allergy and analyzed these studies according to their design, inclusion and exclusion criteria, population studied, variables or factors tested, method of intervention or treatment with vitamin C, and results and conclusions. We reviewed our data and divided it based on significant or insignificant roles of vitamin C in asthma and allergy. RESULTS: From our review, we found a number of studies that support the use of vitamin C in asthma and allergy. Significant results include positive effects on pulmonary function tests, bronchoprovocation challenges with methacholine or histamine or allergens, improvement in white blood cell function and motility, and a decrease in respiratory infections. Our review also revealed several studies that did not support a beneficial role in vitamin C in asthma and allergy. These studies did not report improvements in pulmonary function tests or bronchoprovocation challenges. No benefit was noted in these studies when testing cutaneous reactivity or specific immunologic factors and levels. CONCLUSIONS: Clearly from our review, the role of vitamin C in asthma and allergy is not well defined. The majority of the studies were short term and assessed immediate effects of vitamin C supplementation. Long term supplementation with vitamin C or delayed effects need to be studied. Although, the current literature does not support a definite indication for the use of vitamin C in asthma and allergy, the promising and positive studies revive curiosity and interest. With a large portion of health care dollars being spent on alternative medicine and vitamin C in particular, further studies are needed to define its role.