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Vitamin C may alleviate exercise-induced bronchoconstriction: a meta-analysis.


ABSTRACT:

Objective

To determine whether vitamin C administration influences exercise-induced bronchoconstriction (EIB).

Design

Systematic review and meta-analysis.

Methods

MEDLINE and Scopus were searched for placebo-controlled trials on vitamin C and EIB. The primary measures of vitamin C effect used in this study were: (1) the arithmetic difference and (2) the relative effect in the postexercise forced expiratory volume in 1 s (FEV1) decline between the vitamin C and placebo periods. The relative effect of vitamin C administration on FEV1 was analysed by using linear modelling for two studies that reported full or partial individual-level data. The arithmetic differences and the relative effects were pooled by the inverse variance method. A secondary measure of the vitamin C effect was the difference in the proportion of participants suffering from EIB on the vitamin C and placebo days.

Results

3 placebo-controlled trials that studied the effect of vitamin C on EIB were identified. In all, they had 40 participants. The pooled effect estimate indicated a reduction of 8.4 percentage points (95% CI 4.6 to 12) in the postexercise FEV1 decline when vitamin C was administered before exercise. The pooled relative effect estimate indicated a 48% reduction (95% CI 33% to 64%) in the postexercise FEV1 decline when vitamin C was administered before exercise. One study needed imputations to include it in the meta-analyses, but it also reported that vitamin C decreased the proportion of participants who suffered from EIB by 50 percentage points (95% CI 23 to 68); this comparison did not need data imputations.

Conclusions

Given the safety and low cost of vitamin C, and the positive findings for vitamin C administration in the three EIB studies, it seems reasonable for physically active people to test vitamin C when they have respiratory symptoms such as cough associated with exercise. Further research on the effects of vitamin C on EIB is warranted.

SUBMITTER: Hemila H 

PROVIDER: S-EPMC3686214 | biostudies-literature | 2013 Jun

REPOSITORIES: biostudies-literature

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Publications

Vitamin C may alleviate exercise-induced bronchoconstriction: a meta-analysis.

Hemilä Harri H  

BMJ open 20130620 6


<h4>Objective</h4>To determine whether vitamin C administration influences exercise-induced bronchoconstriction (EIB).<h4>Design</h4>Systematic review and meta-analysis.<h4>Methods</h4>MEDLINE and Scopus were searched for placebo-controlled trials on vitamin C and EIB. The primary measures of vitamin C effect used in this study were: (1) the arithmetic difference and (2) the relative effect in the postexercise forced expiratory volume in 1 s (FEV1) decline between the vitamin C and placebo perio  ...[more]

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