New research suggests that vitamin C may reduce bronchoconstriction and respiratory symptoms caused by exercise, according to a recent study.

Researchers from the University of Helsinki found that vitamin C halved post-exercise FEV1 decline in participants who suffered from exercise-induced bronchoconstriction. FEV1 is the pulmonary function outcome for assessing whether a person suffers from exercise-induced bronchoconstriction.

Physical activity increases oxidative stress, and therefore, as an antioxidant vitamin C might have particularly evident effects on people who are participating in vigorous exercise. In previous studies, vitamin C administration attenuated the increases in oxidative stress markers caused by exercise.

A meta-analysis of three studies and found that vitamin C reduced post-exercise FEV1 decline in participants who suffered from exercise-induced bronchoconstriction. Five other studies examined subjects who were under short-term, heavy physical stress and a meta-analysis revealed that vitamin C halved the incidence of respiratory symptoms. Another trial reported that vitamin C halved the duration of the respiratory symptoms in male adolescent competitive swimmers.

For the study, researcher Harri Hemila carried out a secondary analysis of a study which had 12 participants. The participants had asthma, were on average 26 years old, and suffered from exercise-induced bronchoconstriction. The FEV1 and FEF60 levels before and after exercise were reported on vitamin C and placebo days, but the data was not thoroughly analyzed originally.

She found that in five out of the 12 participants, exercise caused a decline greater than 60 percent in FEF60. Such a decline indicates that the absolute post-exercise level of FEF60 becomes an important outcome in its own right, in addition to its change from the pre-exercise level. Vitamin C administration increased the post-exercise FEF60 level in these five participants by between 50 and 150 percent.

 In contrast, no mean difference between the vitamin C and placebo days was detected in the other seven participants. The increase in post-exercise FEF60 level by vitamin C is a novel finding, which indicates that vitamin C may have substantial effects on the small airways.

"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," Hemila said.