Winter illness and vitamin C: the effect of relatively low doses

After their random -llocation to one of three treatment aroups, 622 volunteers received either vitamin C or placebo in a maintenance dose of 500 mg once weekly and a therapeutic dose of 1500 mg daily on the 1st day and 1000 mg on the next 4 days of any illness. Two forms of vitamin C were employed: a sustained-release capsule containing ascorbic acid and a regular tabet containing a mixture of sodium and calcium ascorbate. In the 448 subjects who completed an average of 15 weeks in the study of total of 635 episodes of illness were recroded. Respiratory symptoms were recorded on at least 1 day in 92 per cent of these episodes. There were no consistent or significant differences in the sickness experience of the subjects receiving the sustained-release vitamin capsules compared to those receiving the vitamin tablets, but subjects in both vitamin groups experienced less severe illness than subjects in the placebo group, with approximately 25 per cent fewer days spent indoors because of the illness (P smaller than 0.05). These results are compatible with the belief that supplementary vitamin C can reduce the burden of winter illness, but the intake need not be as high as has sometimes been claimed.