Taking extra vitamin C does little to stop most people from catching a cold, according to a new survey, but it helps stop those exposed to extreme physical conditions from coming down with the sniffles.
Soldiers and skiers are among those most likely to benefit from taking extra doses of the vitamin and marathon runners are clear winners, said Professor Bob Douglas of the Australian National University.
”The marathon runners are the most impressive and I don’t think we can assume it necessarily protects to the same extent people who are engaged in moderate physical activity and cold stress,” he said.
”But we can be quite confident that for ordinary people it doesn’t make much difference.
”It doesn’t lessen their risk; they might have a very slight reduction in the length of their cold — about half a day or a day.”
The study into the impact of vitamin C in preventing colds and flu, conducted in collaboration with associate professor Harri Hemila of Finland’s University of Helsinki, surveyed 55 other studies carried out over the past 65 years and is the most extensive of its kind.
Almost half of the previous studies show that taking a daily dose of at least 200mg of vitamin C makes no difference to the incidence of the common cold.
But in a subgroup included in six studies, which focussed on people exposed to cold and/or physical stress, vitamin C reduced the illness by half.
About 30 studies noted that eight percent of adults and 13% of children who continued to take vitamin C while they had a cold cut short its duration.
And one study found that if a high dose (eight grams) of vitamin C was taken at the onset of symptoms the length of the illness was cut short.
But overall, Douglas said the findings, published in the June issue of United States-based online medical journal PLoS Medicine, did not justify regular use of vitamin C as a preventative agent.
Vitamin C had not proven to be a ”magic bullet” to solve the common cold, he said. – Sapa-AFP