Maybe. A large number of studies have shown that vitamin C does not prevent the common cold from happening, but it does help curb its severity and duration. If you don’t eat the optimal 9+ fruits and vegetables daily, then take a vitamin C supplement. The effective dose is about 500 milligrams to 2,000 milligrams daily starting at the first signs of a cold and taken in divided doses throughout the day. Discontinue after cold symptoms are gone. That’s only for adults; young children are much more susceptible to toxicity effects from vitamins and minerals, so keep their intake to within Daily Value levels or discuss higher doses with your physician.