Vitamin C does nothing to prevent the common cold but may shorten its duration, Australian and Finnish researchers say in their analysis of 55 studies.
The 1970s book, "Vitamin C and the Common Cold," by Nobel Prize-winning chemist Linus Pauling sparked interest in the supplement that has grown to a more than $600 million annual business in Britain, the Times of London reported.
However, researchers Robert Douglas of Australian National University and Harri Hemila of the University of Helsinki said people who took up to 2 grams of Vitamin C daily caught colds at the same rate as people who took a placebo.
The result "throws doubt on the utility of this wide practice," the authors said in the journal Public Library of Science Medicine.
One study found that very large doses of Vitamin C -- 8 grams -- taken on the first day of a cold appeared to shorten how long it lasts.
Those results are "tantalizing and deserve further investigation," the researchers said.
Copyright 2005 by United Press International
Explore further: Will horseradish and garlic really ease a cold?