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Standard Article
Vitamin C for preventing and treating the common cold
Editorial Group: Cochrane Acute Respiratory Infections Group
Published Online: 19 JUL 2004
DOI: 10.1002/14651858.CD000980
Copyright © 2004 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.
Database Title
Additional Information
How to Cite
Douglas RM, Chalker EB, Treacy B. Vitamin C for preventing and treating the common cold. The Cochrane Database of Systematic Reviews 1998, Issue 2. Art. No.: CD000980. DOI: 10.1002/14651858.CD000980.
Publication History
- Published Online: 19 JUL 2004
This is not the most recent version of the article.View current version (17 Mar 2010)
Abstract
Background
The role of oral ascorbic acid (vitamin C) in the prevention and treatment of colds remains controversial despite many controlled trials. There have also been a number of efforts to synthesize and/or overview the results of these trials, and controversy over what these overviews tell us.
Objectives
The objective of this review was to answer the following two questions:
(1) Does regular high dosage supplementation with vitamin C reduce the incidence of colds?
(2) Does taking vitamin C in high doses at the onset of a cold have a therapeutic effect?
Search strategy
This review currently deals only with published trials from two previously published reviews by Kleijnen 1989 and Hemila 1992.
Selection criteria
Randomised and non-randomised trials of vitamin C taken to prevent or treat the common cold.
Data collection and analysis
Two reviewers independently extracted data and assessed trial quality.
Main results
Thirty trials were included. The quality of the included trials was variable. Vitamin C in doses as high as one gram daily for several winter months, had no consistent beneficial effect on incidence of the common cold. For both preventive and therapeutic trials, there was a consistently beneficial but generally modest therapeutic effect on duration of cold symptoms. This effect was variable, ranging from -0.07% to a 39% reduction in symptom days. The weighted difference across all of the studies revealed a reduction of a little less than half a symptom day per cold episode, representing an 8% to 9% reduction in symptom days. There was no clear indication of the relative benefits of different regimes or vitamin C doses. However in trials that tested vitamin C after cold symptoms occurred, there was some evidence that a large dose produced greater benefits than lower doses.
Reviewers' conclusions
Long term daily supplementation with vitamin C in large doses daily does not appear to prevent colds. There appears to be a modest benefit in reducing duration of cold symptoms from ingestion of relatively high doses of vitamin C. The relation of dose to therapeutic benefit needs further exploration.
Synopsis
Synopsis
Vitamin C does not prevent the common cold, but very high doses probably shorten the length of the illness
Controversy continues over the role of oral ascorbic acid (vitamin C) in preventing and treating colds. Colds are caused by a number of viruses. There is currently no proven cure, although symptoms can be treated. The review found that long-term supplementation with vitamin C in large daily doses does not appear to prevent colds. However, taking relatively high doses of vitamin C probably shortens the length of the illness. More research is needed on how high the dose needs to be to help.