Vitamin C was promoted as a cure for the common cold by a very
famous scientist, Dr. Linus Carl Pauling, in the 1970s. Vitamin C, at high intake levels, has the effect of suppressing inflammation of the blood vessels. A clinical study showed that those who had the highest plasma vitamin C levels or took supplements of vitamin C had much lower levels of inflammatory markers in their bloodstream than those who did not.
The use of vitamin C in the prevention or treatment of the common
cold and respiratory infections remains controversial, and research is ongoing.
This indicates that the efficacy, if any, must be very weak; otherwise, it
would not be a divisive approach to curing colds.
For cold prevention, more than thirty clinical trials including
over ten thousand participants have examined the effects of taking daily
vitamin C. Overall, no significant reduction in the risk of developing colds
has been observed. In people who developed colds while taking vitamin C, no
difference in the severity of symptoms has been seen overall, although a small,
significant reduction in the duration of colds has been reported (approximately
10 percent in adults and 15 percent in children). For cold treatment, numerous
studies have examined the effects of starting vitamin C after the onset of cold
symptoms. So far, significant benefits have not been observed. However,
inflammation is the body’s weapon to fight against cold viruses. Inhibiting
inflammation alone cannot effectively cure the common cold.