Vitamin C pretty useless when it comes to colds

[abdulhakeem]

Medical Research News
Published: Tuesday, 28-Jun-2005

Since the 1970's, when research advocated that doses of Vitamin C would help alleviate symptoms of the common cold, that doctrine has been generally accepted.

But in a recent review of past clinical research on this topic, it is suggested that the public's enthusiasm for vitamin C may be unjustified.

In an attempt to discover whether vitamin C could help in the prevention of a cold, researchers Robert M Douglas, from the Australian National University (http://www.anu.edu.au/), and Harri Hemila of the University of Helsinki (http://www.helsinki.fi/university/), reviewed 23 past studies on vitamin C and the common cold conducted over the last 65 years.

They found that vitamin C did not appear to help the general public in the prevention of colds, but the authors did find evidence that vitamin C could help prevent colds in people exposed to extreme physical exertion, such as marathon runners.

The researchers also found that those people who were given vitamin C and then caught a cold, experienced a small reduction in the duration of the cold compared with those taking a placebo.

In one of the trials, patients who took a single, very high dose of the vitamin (8 g) on the day their symptoms started experienced a shorter illness compared with people who took a placebo pill.

The authors declare the results in this single trial as "tantalizing and deserving of further assessment."

The review is published in this month's open access journal, PLoS Medicine (http://www.plosmedicine.org/).

http://www.news-medical.net/?id=11368

[abdulhakeem]

Regular vitamin C does not prevent colds

10:47 28 June 2005
NewScientist.com news service
Emma Young, Sydney

Regular doses of vitamin C will not prevent a cold in most people - though they might reduce its duration slightly, according to a major new review of existing research.

The idea that the vitamin can prevent and treat a cold became popular following the 1970 publication of Nobel laureate Linus Pauling's book, Vitamin C and the Common Cold. "Pauling's book was very influential. But I'm confident that the general population doesn't stand to gain any great benefit in terms of colds from taking regular doses," says Robert Douglas of the Australian National University in Canberra, who co-authored the review.

Douglas and Harri Hemilä of the University of Helsinki, Finland, considered 55 studies dating from 1940 to 2004. These studies compared the effect of at least 200 milligrams daily versus a placebo.

From 23 studies investigating prevention in the general population, the pair concluded that regular doses of vitamin C do not reduce the risk of a cold. But they found the duration of any cold that did develop was shortened, though "only by about half a day in adults, and slightly more in children", Douglas notes.

Extreme physical stress

However, people suffering extreme physical stress through exertion or freezing temperatures did benefit substantially from taking vitamin C. Studies of skiers, soldiers and marathon runners suggest that regular vitamin C can slash their incidence of colds in half. Pauling was heavily influenced by a ski school study, in particular.

"I don't understand why - but it does seem there is a small subset of people who do seem to have substantial prevention benefit from taking vitamin C, when for the general population it's zilch," Douglas says.

As well as considering the effect of regular daily does, the pair also looked at whether starting to take vitamin C as soon as a symptoms appeared could shorten a cold. They found no evidence that it could, except for in one study which involved a huge 8 gram dose on the first day of symptoms.

"For all except this 8 gram group, the evidence is quite unimpressive that taking largish doses makes any difference at all once a cold has started," says Douglas.

Journal reference: PLoS Medicine (Vol 2(6), p e68)

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[abdulhakeem]

Scientists go cold on vitamin C

June 28, 2005
By Mark Henderson, Science Correspondent

ONE of the most enduring health notions has been exposed as a myth: research has found that vitamin C will do nothing to stop you catching a cold.


A review of 55 studies has shown that even large regular doses of the vitamin do not reduce the risk of contracting a common cold.

People who took daily doses of up to 2g of vitamin C — 33 times more than the recommended daily amount — caught colds at the same rate as those who took an inert placebo instead, the analysis shows.

The findings, by Robert Douglas, of the Australian National University in Canberra, and Harri Hemilä, of the University of Helsinki, suggest that enthusiasm for vitamin C supplements to stave off winter colds is misplaced. “The lack of effect of prophylactic vitamin C supplementation on the incidence of common cold in normal populations throws doubt on the utility of this wide practice,” the authors said.

The scientists did find some evidence that people who took regular vitamin C suffered slightly shorter colds than those who take placebos, though the clinical significance was judged questionable. There was also a preventive effect on people who engage in extreme exertion in cold weather, such as soldiers, skiers and marathon runners, though it was impossible to draw conclusions from this for general health.

Vitamin C became fashion-able as a means of preventing colds in the 1970s, after the Nobel Prizewinning chemist Linus Pauling published his book Vitamin C and the Common Cold. Dr Pauling proposed that large doses of vitamin C would protect against colds and cut their duration.

His advice is followed by millions. It is one of the biggest elements of a supplement market worth £350 million a year in Britain.

Evidence for the preventive worth of vitamin C, however, has always been sparse, and the new survey suggests that such an effect does not actually exist.

Dr Douglas and Dr Hemilä undertook the investigation for the Cochrane Review, which attempts to combine the evidence from many high-quality studies to provide an overall picture of which medical treatments work. Their findings appear today in the journal Public Library of Science Medicine.

They identified 55 controlled studies of sufficient rigour, of which 23 dealt explicitly with vitamin C supplements and cold prevention. For the general population, they found that this regime brought no benefits. Vitamin C is also little use for stopping a cold, the review suggests: in seven studies, no consistent benefit was found.

One of the trials, however, did find that a very large dose of vitamin C — of 8g — on the first day of cold symptoms appeared to shorten its duration. Those results, the scientists said, were “tantalising and deserve further investigation”

http://www.timesonline.co.uk/article/0,,2-1671812,00.html