The authors of the Cochrane review concluded that "...given the consistent effect of vitamin C on the duration and severity of colds in the regular supplementation studies, and the low cost and safety, it may be worthwhile for common cold patients to test on an individual basis whether therapeutic vitamin C is beneficial for them." Vitamin C distributes readily in high concentrations into immune cells, has antimicrobial and natural killer cell activities, promotes lymphocyte proliferation, and is consumed quickly during infections, effects indicating a prominent role in immune system regulation.
The European Food Safety Authority found a cause and effect relationship exists between the dietary intake of vitamin C and functioning of a normal immune system in adults and in children under three years of age.
Notable human dietary studies of experimentally induced scurvy have been conducted on conscientious objectors during World War II in Britain and on Iowa state prisoners in the late 1960s to the 1980s.
Scurvy was known to Hippocrates in the classical era.
The disease was shown to be prevented by citrus fruit in an early controlled trial by a Royal Navy surgeon, James Lind, in 1747, and from 1796 lemon juice was issued to all Royal Navy crewmen.
Doing so converts vitamin C to an oxidized state - either as semidehydroascorbic acid or dehydroascorbic acid.
These compounds can be restored to a reduced state by glutathione and NADPH-dependent enzymatic mechanisms.