Vitamin C and common cold-induced asthma: a systematic review and statistical analysis

Abstract

BackgroundAsthma exacerbations are often induced by the common cold, which, in turn, can be alleviated by vitamin C.ObjectiveTo investigate whether vitamin C administration influences common cold-induced asthma.MethodsSystematic review and statistical analysis of the identified trials. Medline, Scopus and Cochrane Central were searched for studies that give information on the effects of vitamin C on common cold-induced asthma. All clinically relevant outcomes related to asthma were included in this review. The estimates of vitamin C effect and their confidence intervals [CI] were calculated for the included studies.ResultsThree studies that were relevant for examining the role of vitamin C on common cold-induced asthma were identified. The three studies had a total of 79 participants. Two studies were randomized double-blind placebo-controlled trials. A study in Nigeria on asthmatics whose asthma attacks were precipitated by respiratory infections found that 1 g/day vitamin C decreased the occurrence of asthma attacks by 78% (95% CI: 19% to 94%). A cross-over study in former East-Germany on patients who had infection-related asthma found that 5 g/day vitamin C decreased the proportion of participants who had bronchial hypersensitivity to histamine by 52 percentage points (95% CI: 25 to 71). The third study did not use a placebo. Administration of a single dose of 1 gram of vitamin C to Italian non-asthmatic common cold patients increased the provocative concentration of histamine (PC20) 3.2-fold (95% CI: 2.0 to 5.1), but the vitamin C effect was significantly less when the same participants did not suffer from the common cold.ConclusionsThe three reviewed studies differed substantially in their methods, settings and outcomes. Each of them found benefits from the administration of vitamin C; either against asthma attacks or against bronchial hypersensitivity, the latter of which is a characteristic of asthma. Given the evidence suggesting that vitamin C alleviates common cold symptoms and the findings of this systematic review, it may be reasonable for asthmatic patients to test vitamin C on an individual basis, if they have exacerbations of asthma caused by respiratory infections. More research on the role of vitamin C on common cold-induced asthma is needed.

Vitamin C may reduce the duration of mechanical ventilation in critically ill patients: a meta-regression analysis

“…For calculations, see Additional file 2. RoM ratio of means [22] with common cold patients indicated that the bronchodilatory effect of vitamin C was most beneficial for those with the greatest bronchial hypersensitivity to histamine [35,36].…”

Deficiency of vitamin D and vitamin C in the pathogenesis of bronchial asthma

“…Bronchial hyperresponsiveness after methacholine challenge was not signifi cantly affected. Another report stated that it may be "reasonable" in patients with BA exacerbated by common cold, to use vitamin C (13). This effect of vitamin C was less obvious when the same individuals with BA did not suffer from the common cold.…”

Relationship between Vitamin C, Mast Cells and Inflammation

“…Administration of vitamin C decreases bronchial hypersensitivity caused by the common cold [40], an effect also mediated by mast cells. In addition it shortens the duration of colds, prevents pneumonia, and decreases the incidence of sneezing, runny nose, cough and other symptoms, all effects related to MC activation.…”