- prevent or reduce the frequency of the common cold, or
- lessen the duration and severity of the common cold.
But is there any evidence that vitamin C supplements work?
In Jan 2013 the Cochrane Collaboration* published online the results of a meta-analysis of twenty-nine vitamin C supplement trials involving a total of 11,306 participants. The only trials included were those using at least 0.2 g of vitamin C per day, and the majority were randomised, double-blind trials.
- Regular use of vitamin C supplements does not reduce the incidence of colds in the general population.
- Regular use of vitamin C may be useful for people exposed to brief periods of severe physical exercise such as marathon running or skiing.
- Regular use of vitamin C supplements has a modest but consistent effect in reducing the duration of common cold symptoms. (Average 8%)
- The published trials have not reported adverse effects of vitamin C.
So for the vast majority of the population, if you regularly take at least two 1000mg tablets of vitamin C per day you will still get the same number of colds, but they will last for about 6½ days instead of 7.
At $0.20 per 1000mg tablet, the cost for a family of four would be almost $600 per year.
*Who is the Cochrane Collaboration? An organisation that does systematic reviews of all studies on particular subjects to produce what are called meta-studies.