Preventing colds: Washing your hands is more effective than taking vitamins
Vitamin C cannot prevent colds / Benefit of vitamins and dietary supplements is often overestimated
Many people have started taking vitamin C tablets as a precautionary measure. But research has shown that vitamin supplements do not provide nearly as much protection as other measures, like frequently washing your hands -- and that high doses can even be harmful. The German Institute for Quality and Efficiency in Health Care has published information and a quiz on the subject of prevention, helping to separate widespread myths from facts.
More information on colds