Oral magnesium and vitamin C supplements in asthma: a parallel group randomized placebo-controlled trial.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 14519140 · doi:10.1046/j.1365-2222.2003.01777.x
What was done
A double-blind, parallel-group, randomized placebo-controlled trial compared 16 weeks of daily supplementation with 1 g/day vitamin C, 450 mg/day magnesium chelate, or matched placebo. The study recruited 300 patients aged 18–60 years with physician-diagnosed asthma using at least one daily dose of inhaled corticosteroids across 24 primary care practices in Nottingham, UK. Outcome measures included forced expiratory volume in 1 s, forced vital capacity, airway responsiveness to methacholine, morning and evening peak flow, symptom scores, and bronchodilator use.
What was found
The abstract reports no numerical values, effect sizes, or confidence intervals. It states that there was no evidence of any beneficial effect of either vitamin C or magnesium supplementation on any outcome measure of asthma control, analyzed both individually and as a combined summary statistic, in primary intention-to-treat and completer-only analyses.
Why it matters
Observational associations between higher dietary intake of vitamin C or magnesium and lower asthma risk do not translate to clinical efficacy when added to standard primary care asthma management.
Limits
The abstract reports no quantitative values or confidence intervals to assess the precision of the null findings. The trial only evaluated a single dose and duration (16 weeks) in adults already maintained on inhaled corticosteroids, and baseline micronutrient or deficiency status was not reported.
Cited by
- contradicts Having adequate magnesium has been shown to improve asthma.