Abstract
BackgroundWe previously found a significant benefit of vitamin C supplementation in asthmatic children.PurposeTo test whether the effect of vitamin C on asthma is heterogeneous over the participant population.MethodsEgyptian asthmatic children between 7 and 10 years of age (n = 60) were included in the cross-over trial. They were administered 0.2 grams per day of vitamin C and placebo for separate 6-week periods. The variation in the vitamin C effect on two clinically relevant outcomes was analyzed: the childhood asthma control test (C-ACT), which measures the severity of asthma symptoms (the scale ranges from 0 to 27 points, < 20 points indicating unsatisfactory asthma control), and FEV1. We used linear modeling to examine the variation of the vitamin C effect in the subgroups.ResultsThe effect of vitamin C on the C-ACT was significantly modified by age and baseline C-ACT levels. In the children aged 7.0-8.2 years with a baseline C-ACT of 18 to 19 points, vitamin C increased the C-ACT score by 4.2 points (95% CI: 3.3-5.3); whereas in the children aged 8.3-10 years who had a baseline C-ACT of 14 to 15 points, vitamin C increased the C-ACT score by only 1.3 points (95% CI: 0.1-2.5). The effect of vitamin C on the FEV1 levels was significantly modified by age and exposure to dampness. In the children aged 7.0-8.2 years with no exposure to dampness, vitamin C increased the FEV1 level by 37% (95% CI: 34-40%), whereas in the children aged 8.3-10 years with exposure to dampness or mold in their bedroom more than one year prior to the study, vitamin C increased the FEV1 level by only 21% (95% CI: 18-25%).ConclusionsWe found strong evidence that the effect of vitamin C on asthmatic children is heterogeneous. Further research is needed to confirm our findings and identify the groups of children who would receive the greatest benefit from vitamin C supplementation.
Highlights
We previously found a significant benefit of vitamin C supplementation in asthmatic children.Purpose: To test whether the effect of vitamin C on asthma is heterogeneous over the participant population
We have previously carried out a placebo-controlled cross-over trial in which we examined the effect of vitamin C, zinc, omega-3 fatty acids and their combination in Egyptian asthmatic children [20]
Supplementation increased the asthma symptom score, childhood asthma control test (C-ACT), by 3.0 points (Table 2). This effect was modified by the baseline C-ACT so that vitamin C was more effective in those children who had less severe asthma symptoms
Summary
Purpose: To test whether the effect of vitamin C on asthma is heterogeneous over the participant population. There is no well-defined mechanism whereby vitamin C may have an effect on asthma. In asthmatic patients, the level of vitamin C is low in plasma [1,16,17,18] and bronchoalveolar fluid [19]. Such a correlation does not imply a causal relationship, it encourages research on vitamin C and asthma. The question about the time of exposure to dampness had two alternatives: 1) “during the past 12 months” and 2) “only earlier” (i.e. more than one year prior to the study); only one child chose both the recent and earlier exposure alternatives
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