On 2015 Mar 10, Harri Hemila commented:

Vitamin C may help against exercise-induced bronchoconstriction

Boulet LP, 2015 reviewed the treatment options for exercise-induced bronchoconstriction (EIB) and stated that there is insufficient data to recommend vitamins or antioxidants as treatment. This statement is misleading.

Three randomized trials examined the effect of vitamin C on exercise-induced FEV1 decline in asthmatics, see Schachter EN, 1982, Cohen HA, 1997, and Tecklenburg SL, 2007. Each trial found that vitamin C halved the FEV1 decline, with the pooled estimate indicating a reduction of postexercise FEV1 decline by 48% (95%CI: 33% to 64%), see Hemilä H, 2013 and Hemila H, 2014. The studies were carried out in three different decades and on two different continents, and the mean ages of the participants were 14 yr in Cohen HA, 1997 and 25-26 yr in Schachter EN, 1982 and Tecklenburg SL, 2007. It is not evident how far the estimate of effect can be generalized, but similar findings from such dissimilar studies indicate that vitamin C may be effective for a wider population who suffer from EIB.

Boulet LP, 2015 refers to the Cochrane review by Wilkinson M, 2014 as a justification for the statement that there are insufficient data on vitamins or antioxidants as treatment of EIB. However, Wilkinson M, 2014 does not include any of the above mentioned three RCTs in their analyses, since their analysis is restricted to studies that used both vitamin C and vitamin E together. Those studies are not relevant to the question whether vitamin C alone has effects on EIB.

Given the safety and low cost of vitamin C and the consistency in the findings of the three RCTs on vitamin C and EIB, it would seem reasonable to encourage physically active people to test whether vitamin C is beneficial on an individual basis, if they suffer from EIB.

On 2015 Mar 10, Harri Hemila commented:

Vitamin C may help against exercise-induced bronchoconstriction

Boulet LP, 2015 reviewed the treatment options for exercise-induced bronchoconstriction (EIB) and stated that there is insufficient data to recommend vitamins or antioxidants as treatment. This statement is misleading.

Three randomized trials examined the effect of vitamin C on exercise-induced FEV1 decline in asthmatics, see Schachter EN, 1982, Cohen HA, 1997, and Tecklenburg SL, 2007. Each trial found that vitamin C halved the FEV1 decline, with the pooled estimate indicating a reduction of postexercise FEV1 decline by 48% (95%CI: 33% to 64%), see Hemilä H, 2013 and Hemila H, 2014. The studies were carried out in three different decades and on two different continents, and the mean ages of the participants were 14 yr in Cohen HA, 1997 and 25-26 yr in Schachter EN, 1982 and Tecklenburg SL, 2007. It is not evident how far the estimate of effect can be generalized, but similar findings from such dissimilar studies indicate that vitamin C may be effective for a wider population who suffer from EIB.

Boulet LP, 2015 refers to the Cochrane review by Wilkinson M, 2014 as a justification for the statement that there are insufficient data on vitamins or antioxidants as treatment of EIB. However, Wilkinson M, 2014 does not include any of the above mentioned three RCTs in their analyses, since their analysis is restricted to studies that used both vitamin C and vitamin E together. Those studies are not relevant to the question whether vitamin C alone has effects on EIB.

Given the safety and low cost of vitamin C and the consistency in the findings of the three RCTs on vitamin C and EIB, it would seem reasonable to encourage physically active people to test whether vitamin C is beneficial on an individual basis, if they suffer from EIB.