Question: Should I take more vitamin C if I feel like I'm coming down with a cold or throughout cold and flu season?
Answer: There's a substantial amount of anecdotal evidence and some scientific evidence for the value of vitamin C. Many people do increase their vitamin C dose at the first sign of a cold, and they take 1,000 milligrams or more of vitamin C and find it of help. However, a meta-analysis that was done in 2004 which looked at 30 placebo controlled randomized trials of vitamin C did not show that it would reduce the incidence of a cold. The downsides are few; occasionally vitamin C upsets peoples' stomach. Very, very rarely, people have increased kidney stones when they take vitamin C. But many people do find that this is a value at the first sign of a cold.