You may have known this intuitively already, but now the results of five randomized trials on participants with heavy short-term physical stress have confirmed that vitamin C reduces the incidence of common cold by 50%.
Three of these trials looked at marathon runners, one studied Swiss school children in a skiing camp and one examined Canadian soldiers during a winter exercise.
Not only that, in a recent randomized trial carried out with adolescent competitive swimmers, vitamin C was shown to halve the duration of colds in men, although it had no effect on women.
Vitamin C is a powerful antioxidant that recycles other vitamins, for example vitamin E. It also strengthens the immune system. Vitamin C is found naturally in high levels in many fruits and vegetables including oranges, blueberries, broccoli, sweet potatoes, tomatoes, cantaloupe and papaya, among others.
According to an updated Cochrane Review, vitamin C seems to be particularly beneficial for people who are experiencing heavy physical stress. Regular doses of vitamin C of one gram per day or higher were shown to decrease the average duration of colds in adults by 8% and in children by 18%.
At the same time, taking vitamin C every day to shorten infrequent colds may not be advisable. On average, adults have only a few common cold episodes per year and children typically only have some half a dozen colds per year.
The results of therapeutic trials - in which vitamin C was given after the first symptoms of a cold appeared - are not consistent.
However, given the consistent beneficial effects of vitamin C on duration and severity of colds in supplementation studies as well as the safety and low cost of vitamin C - it may be worthwhile to figure out for yourself whether therapeutic vitamin C is beneficial for you, when you’re suffering through an episode of common cold.