A new review shows that regular vitamin C supplementation seems to have a consistent effect in reducing the duration and severity of common cold symptoms. A significant reduction in incidences of the common cold has been shown for people with heavy, short-term physical stress.
In meta-analyses, the results of several randomized controlled trials were analyzed to investigate whether vitamin C reduces the incidence, duration or severity of the common cold when used either as a continuous regular supplementation every day or as a therapy at the onset of cold symptoms (1). The data analyses showed that while regular vitamin C supplementation (0.2 to 2 g/day) did not significantly reduce the incidence of colds in the general population, vitamin C reduced the incidence of common cold by up to 50% among study participants exposed to brief periods of intense physical exercise (e.g., skiers, swimmers or marathon runners). In adults, regular vitamin C intake generally reduced the average duration of colds by 3% to 12% and in children by 7% to 21%. In children, 1 to 2 g/day vitamin C shortened cold duration by 18%. The severity of colds was also reduced with regular vitamin C administration. Trials in which vitamin C was given only after the first symptoms of a cold appeared (therapeutic use), no consistent effect of vita-
min C was seen on the duration or severity of colds.
The researchers commented that as on average, adults have only a few common cold episodes per year and children have some half a dozen colds per year, taking vitamin C every day to shorten infrequent colds may not be reasonable. Nevertheless, given the consistent effect of vitamin C on the duration and severity of colds in the regular supplementation studies, and the safety and low cost of vitamin C, it may be worthwhile for individual physically stressed people and common cold patients to test whether regular or therapeutic vitamin C is beneficial for them.
Since the common cold is usually caused by one of the respiratory viruses, antibiotics are useless and therefore other potential treatment options are of substantial public health interest. Vitamin C has been proposed for preventing and treating respiratory infections since it was isolated in the 1930s. It became particularly popular in the 1970s when Nobel laureate Linus Pauling concluded from earlier placebo-con-trolled trials that vitamin C could prevent and alleviate the common cold. Over two dozen new trials were undertaken thereafter.