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Dr. Tori Hudson, Portland, Oregon, Blog Healthline Blog

Vitamin C letters made of citrus fruits - lemon, grapefruit, orange and kiwi slices on white backgroundNumerous randomized trials over the years have shown that vitamin C shortens the duration of common colds. Some trials reported greater effects on severe cold symptoms compared with mild symptoms. This updated review systematically compares the effects of vitamin C on severe and mild common cold symptoms.

Authors included all placebo-controlled trials of orally administered vitamin C in doses of at least 1 g/day for the common cold for people who were in good health at baseline. The meta-analysis was restricted to trials which reported both the total duration of the common cold, the severity of the cold, the duration of more severe stages of the cold, or proxies for severe colds such as days indoors.

Results

There were fifteen comparisons from 10 trials which reported both mild and severe symptoms.  All trials were randomized and double-blind. Compared to placebo, vitamin C significantly decreased the severity of the common cold by 15%.  The direct comparison of the effect of vitamin C on mild and severe symptoms was limited to five comparisons which found that vitamin C had a significant benefit on the duration of severe symptoms. In this particular subset, there was a significant difference in the size of the effect of vitamin C on the overall duration of colds but not the duration of severe colds.  Vitamin C had no significant effect on the duration of mild symptoms.

Commentary:

The simple common cold is the leading cause of missed work and school.  However, absenteeism often depends on the severity of the symptoms.  The finding from this meta-analysis that vitamin C has a greater effect on more severe symptoms of the common cold is important in that people can tend to stay home only when their symptoms are indeed more severe.  It would be useful to have more data on vitamin C and different levels of severity.  In addition, more research on different doses, as perhaps higher doses might yield better results.  Some individual studies have shown that vitamin C at the early onset of the cold symptoms can shorten the duration and reduce severity.

While we don’t have all the answers on the value of vitamin C in reduction of incidence or reduction of severity and duration, vitamin C is simple, safe, inexpensive and easy to obtain…. and the chance of reducing severity and shorten duration by even just one day, can matter.

Reference: Hemila H, Chalker E.  Vitamin C reduces the severity of common colds: a meta-analysis.  BMC Public Health volume 23, Article number: 2468 (2023)

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