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…and reduce your asthma, new study says.
Exercise causes bronchoconstriction in about 10% of the general population and nearly 50% of some competitive adults. This was known as exercise-induced asthma, but is now known as exercise-induced bronchoconstriction (EIB). It is measured by a decline in forced expiratory volume in 1 second (FEV1). Previous lab studies suggested that vitamin C could reduce the FEV1 decline that follows exercise. This meta-analysis of three randomized, placebo controlled studies with a total of 40 participants found that vitamin C was associated with smaller declines in humans as well. Compared to placebo, vitamin C was associated with an 8.4 percentage points smaller FEV1 decline following exercise and a 48% relative decline. One study looked at the proportion of people who had EIB (defined as at least a 15% decline in postexercise FEV1). When given the placebo all the 20 participants experienced EIB, but only 10 of them did so after taking vitamin C, a 50% reduction. Given the low cost and safety of vitamin C and the consistency of the findings in these studies, the authors say that it “seems reasonable” that fit and active
people with respiratory symptoms after exercise should take vitamin C could to see if it relieves their symptoms.