Does vitamin C stop colds?

The answer is kinda, but not so much. Consuming 200 mg of vitamin C per day (the recommended daily allowance is between 60 and 90 mg), was found to reduce the duration of a cold by only 8% in adults. The vitamin did not reduce the likelihood of getting a cold, except in soldiers, marathon runners, and others under extreme external stress. Given that the average adults only gets one cold per year, it doesn't make sense to swallow 200 mg per day of vitamin C. Humans are unlike most animals in that they can not make their own vitamin C.