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Vitamin C for preventing and treating the common cold
R M Douglas1, E B Chalker, B Treacy
1National Centre for Epidemiology and Population Health, The Australian National University, Canberra, ACT, Australia, 0200. Bob.Douglas@anu.edu.au
The Cochrane Database of Systematic Reviews
|May 5, 2000
Summary
Regular high-dose vitamin C (ascorbic acid) supplementation does not prevent colds. However, taking vitamin C at the onset of cold symptoms may modestly reduce symptom duration.
Area of Science:
- Nutrition Science
- Public Health
Background:
- The efficacy of oral ascorbic acid (vitamin C) for preventing and treating the common cold remains a subject of debate.
- Numerous clinical trials and meta-analyses have addressed this topic, yet consensus is lacking.
Purpose of the Study:
- To determine if regular high-dose vitamin C supplementation reduces cold incidence.
- To assess the therapeutic effect of high-dose vitamin C when taken at the onset of cold symptoms.
Main Methods:
- Systematic review of randomized and non-randomized trials on vitamin C for cold prevention and treatment.
- Data extraction and quality assessment by two independent reviewers, focusing on trials from previous reviews (Kleijnen 1989, Hemila 1992).
Main Results:
- Thirty trials were included, with variable quality.
- High-dose vitamin C (up to 1g daily) showed no consistent effect on cold incidence.
- A modest, variable therapeutic effect was observed in reducing cold symptom duration (8-9% reduction in symptom days).
- Evidence suggests larger doses may be more beneficial when initiated after symptom onset.
Conclusions:
- Long-term, high-dose vitamin C supplementation does not prevent colds.
- Ingesting relatively high doses of vitamin C appears to offer a modest benefit in reducing cold symptom duration.
- Further research is needed to clarify the dose-response relationship for therapeutic benefits.