How much does vitamin c help in preventing the common cold?

To bowel tolerance: Typically, 2000mg per day should be fine. Consider vitamin d and a good multivitamin for prevention as well.

It doesn't: There is no good evidence that vitamin c prevents colds.

It doesn't: This common myth was really kicked into high gear by a physicist named linus pauling who was obsessed with megadoses of vitamin c. Because of the respect he was due as a beloved scientist and nobel prize winner, dr. Pauling's work on vitamin c, which has since been disproven, was given more attention and respect than it was worth. High vit c doses can cause kidney stones and still not help the cold.

None: Vitamin c does not reduce, prevent or change anything about colds. This is one of those great health myths. I have seen at least one patient who was taking mega doses develop a severe rash that resolved when the person stopped it. Does taking a little extra hurt? Usually noit. Will taking a lot help keep you from getting a cold? Probably not.

It might some: It is not a cure all! but there is some evidence that if taken regularly(daily)it might reduce the frequency of colds..But hard scientific evidence for this benefit is lacking.