Vitamin C does little to reduce the length or severity of a cold, a major research review of has concluded.
There has been controversy over the vitamin's potential medical properties since its discovery in 1930, according to the authors of the latest Cochrane Review.
The study is an update of a review of research which has been conducted over several decades, including more than 11,000 people.
They authors said the only people less likely to catch a cold if they took a daily dose of vitamin C were people exposed to periods of high stress, such as marathon runners.
However, a second review concluded that spraying saline into the nose could help reduce congestion accompanying long-term infections of the nasal passages.
Cochrane Database of Systematic Reviews (2007) 3