Cochrane LibraryCommon ColdExerciseVitamins

Here’s what we know about vitamin C and the common cold

150px-Ascorbic_acid_structureVitamin C (ascorbic acid) for preventing and treating the common cold has been a subject of controversy for 70 years.

Now, The Cochrane Library has reviewed the data.

First, the details.

  • 29 studies involving 11,306 participants contributed to the meta-analysis on the risk of developing a cold while taking vitamin C regularly.
  • 31 comparisons examined the effect of regular vitamin C use on common cold duration (9745 episodes).
  • The majority of included studies were randomized, double-blind — neither the researchers nor patients knew the treatment given.

And, the results.

  • Regular ingestion of vitamin C had no effect on common cold incidence in the ordinary population.
  • Regular supplementation of at least 1 gram of vitamin C daily had a modest but consistent effect in reducing the duration of common cold symptoms in adults (8%) and in children (18%).
  • In participants exposed to short periods of extreme physical stress (including marathon runners and skiers) vitamin C reduce the common cold risk by up to half in some but not all studies.
  • No adverse effects of vitamin C were reported.

The bottom line?

Based on what we know it appears there is no evidence that regular supplementation of vitamin C reduces the chance of coming down with a common cold, although it may reduce the duration and severity of illness.

The effect on people in extreme exercise situations is inconsistent.

2/14/13 09:06 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.