Vitamin C could prevent colds in athletes who train intensively

In his book "Vitamin C and the common cold", two-time Nobel Prize winner Linus Pauling Vitamin C for the treatment and prevention of the common cold. He claimed that taking 1,000mg of vitamin C reduces the risk of catching a cold by 45 percent. Since then, a number of studies have found that vitamin C does not prevent colds, but may reduce their severity.
Scientists at the University of Helsinki in Finland collected data from 30 studies with a total of more than 11,000 participants who took at least 200mg of vitamin C per day. Vitamin C had no effect on the incidence of colds, but it reduced the length and severity of colds by 8 percent. Vitamin C reduced the risk of colds by 50% in people exposed to high levels of stress, such as soldiers training in the cold or marathon runners. Although vitamin C did not reduce the risk of colds in inactive people, it did have its benefits in intensively training athletes. High doses of vitamin C cause few or no side effects.
(The Cochrane Database of Systematic Reviews, 3: CD000980, 2007)