January 27, 2010

Treating the common cold

Posted in Misc at 07:59 by graham

Will Vitamin C really prevent or cure your cold?

What about Echinacea?

The best way to find out is to follow these simple steps:

  1. Gather 2000 people who have the common cold
  2. Split them randomly into two groups of 1000
  3. Give vitamin C to one group, and a sugar pill (the placebo) to the other
  4. Make sure the people receiving the pills and those dispensing the pills don’t know which is which (to make your trial double-blind)
  5. Wait a bit
  6. See if the Vitamin C group gets over their colder faster than the other group

You will of conducted a double-blind placebo controlled scientific trial.

Luckily for us, we don’t have to do it ourselves. Several of these trials have already been done. Enough trials, in fact, that one can do a Meta analysis, a statistical review and summary of all the trials.

A comprehensive meta analysis, by an unbiased organization, is the gold standard of scientific inquiry; it is our best chance of knowing the truth.

The Cochrane Collaboration is an international not for profit organisation set up 15 years ago to create transparent, systematic, unbiased reviews of the medical literature on everything from drugs, through surgery, to community interventions. And I have a cold. I read their review to find out whether Vitamin C or Echinacea would be effective in treating it.

Vitamin C

Here is the review of research on Vitamin C for preventing and treating the common cold.

Thirty trials involving 11,350 participants suggest that regular ingestion of vitamin C has no effect on common cold incidence in the ordinary population. It reduced the duration and severity of common cold symptoms slightly, although the magnitude of the effect was so small its clinical usefulness is doubtful. Nevertheless, in six trials with participants exposed to short periods of extreme physical or cold stress or both (including marathon runners and skiers) vitamin C reduced the common cold risk by half. The failure of vitamin C supplementation to reduce the incidence of colds in the normal population indicates that routine mega-dose prophylaxis is not rationally justified for community use. But evidence suggests that it could be justified in people exposed to brief periods of severe physical exercise or cold environments.


Here is their review of research on Echinacea for preventing and treating the common cold.

Echinacea preparations tested in clinical trials differ greatly. There is some evidence that preparations based on the aerial parts of E. purpurea might be effective for the early treatment of colds in adults but the results are not fully consistent. Beneficial effects of other Echinacea preparations, and Echinacea used for preventative purposes might exist but have not been shown in independently replicated, rigorous RCTs.

Get well soon!

1 Comment »

  1. Jeremy said,

    February 3, 2010 at 17:49

    I love this, what a great way to get research summaries.

    Though I do object to this statement:

    “A comprehensive meta analysis, by an unbiased organization.”

    The social scientist in me rejects the notion of even the most empirical of examinations being unbiased.

    Check out Thomas Kuhn, and his study of scientific paradigms, and the subjectivity of science.

    Okay, done being contrarian. Nice find. I do agree it’s much better than reading a single study. Though presumably a single study has been peer reviewed by people who should know about all of the studies.

    This is much more transparent though, no presumptions, they tell you what the studies are, and defend their assumptions.

    I wonder if publicly available meta-analysis is a replacement to the peer review process? Because it is more transparent…

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