The common cold is a leading cause of doctor's visits and a major cause for absences from work and school. Since its identification in the early part of the previous century, there was interest in the possible effects of vitamin C against the common cold. In placebo-controlled trials, vitamin C has shortened the duration and severity of colds. Vitamin C has not decreased the frequency of colds in the general community, but it has halved the frequency of colds in studies which examined people under heavy short-term physical stress.
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Background
Vitamin C was identified in the early part of the previous century and there was much interest in its possible effects on various infections including the common cold. A few controlled trials on the effect of vitamin C on the common cold were carried out already in the 1940s, but the topic became particularly popular after 1970, when Linus Pauling, a double Nobel laureate, wrote a best-selling book Vitamin C and the Common Cold. Pauling's book led to great interest in the topic among lay people, but also among academic circles. After Pauling's book, a number of controlled trials were carried out. However, the interest disappeared after the middle of 1970s apparently due to the publication of two reviews and one primary study, which all concluded that vitamin C does not influence the common cold. However, the three papers were later shown to be erroneous.
Research findings
According to the Cochrane review on vitamin C and the common cold, 1 g/day or more of vitamin C does not influence common cold incidence in the general community. However, in five randomized double-blind placebo-controlled trials with participants who were under heavy short-term physical stress, vitamin C halved the incidence of colds. In the dose of 1 g/day or more, vitamin C shortened the duration of colds in adults by 8% and in children by 18%. Vitamin C also decreased the severity of colds.