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Vitamin C does not prevent or cure the common cold

A major review of the evidence has found that taking vitamin C supplements does not prevent people catching colds, and doesn’t cure them, either, although it might help your cold clear up slightly sooner.
By Grant Stewart

BMJ Group News

What do we know already?

vitamin c pills

The common cold is a major cause of illness, and of time off work and school. It’s not usually serious, and it clears up by itself. But the symptoms can be unpleasant and exhausting.

There are about 200 viruses than can cause cold symptoms, and there isn’t much doctors can do about them. Antibiotics are useless against colds - antibiotics fight bacteria but can’t help against viruses. Over-the-counter treatments like paracetamol and decongestants can treat some of the symptoms, but they aren’t a cure.

Doctors have been looking at whether vitamin C helps prevent and treat colds for about 70 years, and studies have found different results. This review looked at 29 studies containing a total of 11,300 people. The studies compared people who took vitamin C to prevent and treat colds with others who took a dummy, or ‘placebo’ treatment. The researchers looked at:

  • How many people in each group had at least one cold
  • How long people’s colds lasted, and
  • How severe their colds were.

What does the new study say?

The review found that taking regular vitamin C supplements did not stop people from catching a cold.

Some of the studies in the review did find that taking vitamin C might help prevent some people catching a cold while doing brief periods of heavy physical exercise. These studies looked at marathon runners, skiers, and soldiers on exercise in countries with sub-zero temperatures. They found that people in these conditions who had been taking vitamin C were about half as likely to catch a cold as those taking a placebo.

The researchers did find that taking vitamin C regularly might help colds clear up sooner, but not by much. For example, taking vitamin C might mean that your cold would last for nine days rather than 10. But this only worked for people who had been taking vitamin C before they caught a cold. Taking vitamin C to treat a cold after people had caught one made no difference to how long it lasted.

Vitamin C did help to make some of the symptoms of colds less severe. But again, this only worked in people who had been taking supplements regularly before they caught a cold. Taking vitamin C once people already had a cold made no difference to how severe their symptoms were.

How reliable is the research?

This kind of study is called a systematic review. Researchers take the best evidence they can find from smaller studies, and pool the results to give the biggest, most accurate picture possible. It is the most reliable type of research we have.

What does this mean for me?

It’s unlikely that vitamin C supplements will do you any harm. But they’re not likely to stop you catching a cold. If you tend to catch colds a lot, it’s possible that your cold might be slightly shorter and less severe if you take vitamin C regularly. But, sadly, the general message is the same as ever: still no cure - or prevention - for the common cold.

Published on February 01, 2013

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