Does Vitamin C really help with a cold?

Ascorbic acid (or “Vitamin C” as it’s more commonly known) is an essential part of the human diet and is associated with the functioning of the human immune system. Because of the compound’s connection to immune function, there’s a long history of people taking Vitamin C supplements to prevent, mitigate, or shorten numerous illnesses. Of course, the number one sickness people try to treat with Vitamin C is the common cold. But, does Vitamin C really help with the common cold? The answer is complicated, but it’s mostly “no.”


Citrus fruits, like oranges, are high in Vitamin C.
(Image Credit: Evan Amos on English Wikipedia)

As we all know, scientists carry out experiments and studies in order to find relationships between an action and its outcome. Then, they publish their results. What many people don’t know is that, when scientists have published many studies on a particularly difficult issue, they actually start writing studies of the studies. These “meta-analyses” combine the results from dozens or even hundreds of studies in order to draw conclusions based on the findings of numerous experiments carried out by experts all around the world.

Interestingly, whether or not Vitamin C can help with a cold is an issue thorny enough to have resulted in the publication of numerous meta-analyses. A couple I took a look at are here:

These studies of studies actually divide the Vitamin C question into three sub-questions. We’ll consider each in turn.

1) Does taking Vitamin C regularly make you less likely to get a cold?

No. Adding a regular Vitamin C supplement to your diet does absolutely nothing to prevent the common cold. Hemila and Chalker’s conclusion is pretty clear…

The failure of vitamin C supplementation to reduce the incidence of colds in the general population indicates that routine vitamin C supplementation is not justified.

Interestingly, however, this may not hold true for people in extreme conditions. In the case of people exposed to very high levels of physical exertion in cold environments, Vitamin C may help prevent colds. Unless you’re going heli-skiing, however, your daily dose of ascorbic acid probably isn’t going to do much for you.

2) Does taking Vitamin C after you get a cold help get rid of it?

No. Again, Hemila and Chalker were pretty clear…

No consistent effect of vitamin C was seen on the duration or severity of colds in the therapeutic [taken after onset of symptoms] trials.

3) So, does Vitamin C do anything?

Taking Vitamin C regularly won’t help you avoid a cold. And taking it once you get a cold won’t help the cold go away. But there’s at least some evidence that taking a regular Vitamin C supplement can help reduce the duration of the colds that you do get. Heimer et al. write:

We also found that regular vitamin C consumption may reduce the duration of cold symptoms in both adults and children.

The studies in question indicate that people who are taking Vitamin C regularly may experience colds that are 3 to 12% shorter than those experienced by the general population.


Legal Ramifications

Of course, the fact that Vitamin C has very little effect on colds has implications for those selling products containing Vitamin C. Many readers will remember the widespread popularity of a supplement called Airborne about 7 to 8 years ago. The supplement advertised itself as “created by a second grade schoolteacher,” which should have maybe caused people to question its scientific credibility…


You know, this stuff.

So, in 2008, the makers of Airborne got slapped with a $23.3 million settlement in a class-action lawsuit. Whoops! Turns out, there was no credible evidence that Vitamin C (or anything else in the tablets) had any ability to prevent or treat colds – which is exactly what Airborne was advertised to do. And, to make matters worse, levels of Vitamin C in the tablets were so high that they put people taking the supplement according to the directions at risk of developing kidney stones. Whoops again!

The Bottom Line

Vitamin C will not prevent a cold. It will not get rid of a cold if you start taking it after you become ill.  But, if you take Vitamin C regularly, your colds might be slightly shorter… If you were taking Vitamin C regularly before your cold started, you might be able to knock one day off of a ten day cold. It’s not much, but it’s something!

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