Does Vitamin C Treat or Prevent the Common Cold?Complementary and Alternative Therapies Evidence-based Summary
Date of review: April 2006
View the plain language summary of this evidence review below.
View also in PDF format - Vitamin C and Common Cold 2006 (PDF, 31 KB)
Treatment in brief
Vitamin C (ascorbic acid).
The common cold
The common cold is a mild viral infectious disease of the nose and throat. Its symptoms include sneezing; sniffing; a runny or blocked nose; scratchy, sore or phlegmy throat; coughing; headache and a general feeling of unwellness. It will generally last between 3 and 10 days, with residual coughing lasting up to 3 weeks.
Background
The common cold is the leading cause of illness and the main reason for visits to a doctor in Western countries. It is also a major cause of absenteeism from work and school.
The role of oral vitamin C in the prevention and treatment of the common cold has been a subject of argument for at least sixty years. Vitamin C is sold widely for the prevention and treatment of colds.
Since the early 1940s, a large number of studies have examined the possible effects of vitamin C on the common cold.
This report looks at taking vitamin C:
- regularly to prevent colds
- to treat a cold (after the cold symptoms have started).
The evidence
Treatment
There is level 1 evidence from eleven studies in a systematic review that the duration or severity of cold symptoms is not reduced if vitamin C is taken when cold symptoms start.
Prevention
- There is level 1 evidence from twenty-nine studies that regularly taking vitamin C does not reduce the number of common colds occurring in the ordinary population.
- There is level 1 evidence from six studies that regularly taking vitamin C reduces the risk of developing a cold by half in people exposed to short periods of extreme physical and/or cold stress (including marathon runners and skiers).
- There is level 1 evidence from forty-five studies that regularly taking vitamin C reduces the duration and severity of common cold symptoms. However, the size of the effect was small and this raises doubt about its real usefulness.
Other important issues
The small reduction in the duration of the symptoms of a cold in adults (8%) and children (13.6%) may not justify taking vitamin C as a long-term preventative due to the ongoing cost. This means that if a cold normally lasted 10 days then the duration of the cold would be reduced by almost one day if you were an adult and one and a half days if you were a child.
In seven large studies, the number of adverse effects reported was similar in the vitamin C group and the placebo group. This suggests that the adverse events were not caused by taking vitamin C. However, no serious adverse effects were reported. For more information on possible adverse effects see http://1stholistic.com/Nutrition/hol_nutr-toxic-dosages.htm
Regular dietary intake of vitamin C from fruit and other sources is highly variable and despite this intake was not measured in most of the studies.
None of the studies that used vitamin C as a treatment after symptoms of a cold had started was carried out in children.
Key messages
Treatment
| Evidence | Level of evidence |
| There is evidence that taking vitamin C does not reduce either the duration or severity of cold symptoms. | 1 |
Prevention
| Evidence | Level of evidence |
| There is evidence that regularly taking vitamin C does not reduce the number of common colds occurring in the ordinary population. | 1 |
| There is evidence that regularly taking vitamin C does reduce the risk of developing a cold in people exposed to short periods of extreme physical and/or cold stress. | 1 |
| There is evidence that regularly taking vitamin C does reduce the duration and severity of common cold symptoms. | 1 |
Key: Levels of evidence
| 1 | 2 | 3 | 4 |
| Evidence with a high degree of reliability | Evidence with reliability, but open to debate | Some evidence without a high degree of reliability | Some evidence, but based on studies without comparable groups. |
References
The information in this summary was developed by assessing:
DISCLAIMER: This summary does not provide specific medical advice and the information provided should not be used as a substitute for seeking medical advice from a registered health practitioner.
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