Vitamin C Reduces Airway Narrowing

Exercise-induced bronchoconstriction means the transient narrowing of the airways that occurs during or after exercise. Usually, the diagnosis of exercise-induced bronchoconstriction is based on a 10% or greater decline in forced expiratory volume in 1 second (FEV1) caused by exercise.  Previously, vitamin C was found to reduce the incidence of common cold episodes in people enduring heavy short-term physical stress, which suggested that vitamin C might also have other effects on people under heavy physical exertion. Harri Hemila, from the University of Helsinki (Finland), completed a meta-analysis involving three relevant randomized placebo-controlled trials, each of which found that vitamin C halved the FEV1 decline caused by exercise challenge test. The pooled estimate of vitamin C effect indicated a 48% reduction in the FEV1 decline caused by exercise. The study author write that: “Given the safety and low cost of vitamin C, and the positive findings for vitamin C administration … it seems reasonable for physically active people to test vitamin C when they have respiratory symptoms such as cough associated with exercise.”