Vitamin C and the common cold

SUMMARY

Carefully controlled experimental studies have failed to support claims that the intake of large doses of vitamin C will prevent or cure the majority of colds. However, an increased regular intake or a large therapeutic dose at the time of illness may have a small beneficial effect and this effect appears to be on severity rather than frequency or total duration of colds. The magnitude of the effect probably varies between individuals, in different environments, and possibly according to the type of infecting agent. The use of very high doses of vitamin C might be harmful to some individuals, particularly if the intake is prolonged. However, for most people, a modest increase in the regular daily intake or brief episodes of high intake are unlikely to cause harm and may improve resistance to other types of illness, not only the common cold,