[js2]

8.1. Cold and Flu

According to meta-analyses on the topic assessing doses of 200mg vitamin C or more, vitamin C has failed to reduce the frequency of colds in the normal population but was successful in reducing the duration of colds (on average 8-14%);[149][145] when looking at studies investigating extreme physical stress (marathoners and skiiers), the risk of getting a cold was halved (which has been noted in past meta-analyses[144])

http://examine.com/supplements/Vitamin+C/#summary8-0

[smtddr]

That's actually in line with how I use it.

Definitely not a marathoner/skiier but I work out about an hour a day and I never expect Vitamin-C to prevent colds. I only take it after 2 to 3 day of sensing an incoming cold.

[vixen99]

I remember a recent study found that vitamin C had no effect on the period or severity of a cold but zinc did. Seems to be confirmed by this :- https://www.ncbi.nlm.nih.gov/pubmed/15496046