The meta-analysis of available studies on vitamin C published recently in Allergy, Asthma and Clinical Immunology looked at the effects of vitamin C on subjects with respiratory problems after exercise.
The analysis was split into three participant groups: those suffering from exercise-induced bronchoconstricion (based on three studies); subjects under short-term heavy physical stress (based on five studies) and male adolescent competitive swimmers with respiratory symptoms (one study).
Physical activity is known to increase oxidative stress and so the researcher expected that vitamin C as an antioxidant could have particularly evident effects on people exercising vigorously.
The meta-analysis of three studies showed that vitamin C reduced post-exercise FEV1decline by 48% in participants suffering from exercise-induced bronchoconstriction.
FEV1 was the standard pulmonary function outcome used for assessing if a person suffers from exercise-induced bronchoconstriction, the condition which included coughing, wheezing and shortness of breath.
Secondary analysis
The researcher carried out a secondary analysis involving 12 participants who suffered from exercise-induced bronchoconstriction.
In five participants he observed a decline in FEF60 (a pulmatory function measure) greater than 60%. Vitamin C administration increased the FEF60 level in these five but did not affect the remaining seven.
The increase in post-exercise FEF60 level by vitamin C was a novel finding, which indicated that vitamin C may have substantial effects on the small airways, said Harri Hamila, who conducted the meta-analysis.
Other studies
Five other analysed studies looked at people under a short-term physical stress and the results suggested that vitamin C halved the incidence or respiratory symptoms.
The last study revealed that vitamin C halved the duration of the respiratory symptoms in competitive male swimmers.
“Given the safety and low cost of vitamin C, and the consistency of positive findings in the nine randomized trials on vitamin C against exercise-induced bronchoconstriction and respiratory symptoms, it seems reasonable for physically active people to test whether vitamin C is beneficial on an individual basis, if they have documented exercise-induced bronchoconstriction or suffer from respiratory symptoms such as cough or sore throat after taking vigorous exercise,” said Hemila.
Source: Allergy, Asthma & Clinical Immunology
Published online ahead of print doi:10.1186/1710-1492-10-58
"The effect of vitamin C on bronchoconstriction and respiratory symptoms caused by exercise: a review and statistical analysis"
Author: H. Hemilä