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Cochrane Database Syst Rev. 2000;(2):CD000980.

Vitamin C for preventing and treating the common cold.

Author information

1
National Centre for Epidemiology and Population Health, The Australian National University, Canberra, ACT, Australia, 0200. Bob.Douglas@anu.edu.au

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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.

REVIEWER'S 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.

PMID:
10796569
DOI:
10.1002/14651858.CD000980
[Indexed for MEDLINE]

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