A new review of the scientific literature says that taking regular supplements of Vitamin C to prevent colds is not justified unless you are exercising hard or living in an extremely cold place, in which case taking about 200 mg a day may cut your risk by 50 per cent. So it probably works for marathon runners, skiers, soldiers and arctic explorers, but not for most adults.
This is the conclusion of a paper published by the Cochrane Library, an abstract of which is available online in the Cochrane Database of Systematic Reviews.
About 30 years ago Nobel Prize winner and chemist Linus Pauling published his influencial book “Vitamin C and the Common Cold” where he recommended that people take 1 gram of Vitamin C a day as a way to prevent catching a cold.
The authors of this latest review do not say that Pauling was wrong, but perhaps he was over-optimistic.
Professor Harri Hemilä, of the Department of Public Health at the University of Helsinki in Finland and three colleagues reviewed 30 scientific papers covering more than 11,000 participants in trials going back several decades that compared regular use of Vitamin C (at least 200 mg a day) against a placebo.
By pooling the data from the studies they calculated that the risk of catching a cold was only about 4 per cent less likely for an adult who took Vitamin C every day, a barely perceptible difference.
People who caught colds while taking Vitamin C were more likely to experience a small reduction in severity and duration (about 8 per cent for adults and 13 per cent for children) compared to placebo but this benefit was so slight that it did not justify the expense and the bother of taking it every day, said the researchers.
It doesn’t make sense to take vitamin C 365 days a year to lessen the chance of catching a cold,” said Hemilä, according to an article in MedPage Today.
However, when they looked at particular subsets of participants they found that the ones who were undergoing extremes of physical or environmental stress were 50 per cent less likely to catch a cold if they took regular Vitamin C supplements compared to placebo.
Trials exploring the impact on duration and severity of a cold from taking high doses of Vitamin C once symptoms have already started are inconsistent and not of very high quality so it is not possible to say anything useful there according to the researchers.
The researchers conceded that vitamin C, taken by itself or with other supplements, might benefit health in ways other than keep colds at bay. They said they would like to see more research on the effect of vitamin C on children with colds and the effect on pneumonia.
The US National Institutes for Health (NIH) say that vitamin C is essential for several reasons.
First, it helps tissues to grow and heal, for instance to repair tendons, torn ligaments and skin.
The recommended daily amount (RDA) for a man is 90 mg per day and for a woman it is 75 mg.
You can get your RDA’s worth of vitamin C if you make sure you eat plenty of citrus and other fruit like kiwi and strawberries, blackcurrants, and vegetables like cabbage, broccoli, sprouts, bell peppers and leafy vegetables.
The Cochrane Library is run by the Cochrane Collaboration, an international organization that reviews medical research.
“Vitamin C for preventing and treating the common cold.”
RM Douglas, H Hemilä, E Chalker, B Treacy
Cochrane Database of Systematic Reviews 2007 Issue 3
Published by John Wiley & Sons, Ltd.
First published online: 18 July 2007
Written by: Catharine Paddock
Writer: Medical News Today