Vitamin C and asthma in children: modification of the effect by age, exposure to dampness and the severity of asthma

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.

Allergic airway diseases in childhood – marching from epidemiology to novel concepts of prevention

“…When concentrating on micronutrients, the conclusions of different groups are mostly discordant. Although most studies support the protective role of vitamin C (81) and vitamin D (82), others show a heterogeneous results on their benefit (83). A similar discordance can be observed in studies evaluating the advantage of magnesium intake.…”

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“…Although folate deficiency appears to be associated with severe exacerbations, no clinical study has assessed the efficacy of folate supplementation in improving asthma control [ 164 , 165 ]. Vitamin C supplementation (0.2 mg/day) has been shown to provide small improvements in asthma control in a cross-over trial, hence a definitive RCT is warranted to confirm this result [ 166 ]. In an RCT, monthly doses of 60,000 intravenous units (IU) vitamin D significantly reduced the number of exacerbations, requirement for steroids and emergency visits in school-aged children compared to placebo [ 167 ].…”

“…Vitamin A supplementation has not shown an association with lung function in asthma patients [ 118 ]. In asthmatic children the effect of vitamin C supplementation, on FEV 1 may be age dependent [ 166 ]. However, the methodology of the RCTs was poor and insufficient to draw a conclusion [ 189 ].…”

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“…The effect of vitamin C on asthmatic children was heterogeneous. The effect of vitamin C on C‐ACT scores varied with age and baseline C‐ACT scores and effects on FEV1 levels varied with age and exposure to the dampness …”