The Ugly Truth about Vitamin C for the Common Cold

It is an unfortunate and uncomfortable reality that we are headed deep into cold and flu season.  While the flu can be prevented with a simple shot, the cold is another beast entirely.  Despite decades of research, no one has been able to come up with a cure, or even a decent treatment option that can consistently outperform placebo. But that doesn't stop products from being marketed as immune boosters to prevent or shorten the length of your cold. 

Why consider Vitamin C?

The human body is an impressively complex collection of systems that work together to keep you healthy and happy.  When going to war with cold viruses, your immune system mounts attacks on three different fronts. We won't get into the dirty details of those here, but it is worth mentioning that Vitamin C plays a crucial role in two of those three fronts. Therefore, it seems to make sense that taking supplemental Vitamin C can 'boost' your immune system and help your body to win its battles against the evil cold virus. As a medication, Vitamin C is relatively cheap and has few side effects making it an easy option to consider when faced with the early symptoms of a cold.

Let’s go deeper (into the data)

Research shows that this easy solution isn’t really a solution at all. Study after study has shown that if you take Vitamin C only when you notice cold symptoms starting, it has no effect on your cold.  Daily dosing of vitamin C (meaning you've taken it for at least 28 days in a row prior to cold season starting) has been shown to reduce the length of cold symptoms by 8% (which if consider the average duration of symptoms is 10 days, results in you getting over your cold symptoms approximately 20 hours sooner.)  Not a lot of return on your investment if you ask me.

Who does Vitamin C work for?

In an effort to find some positive effects of Vitamin C, researchers looked closely at different characteristics of the people participating in the studies.  When looking at athletes, an interesting trend appeared. When marathoners, triathletes, and bodybuilders were given daily vitamin C supplements, their risk of catching a cold was cut in half!  This amazing reduction in cold symptoms was thought to be due to the fact that strenuous exercise causes the body to use up its stores of Vitamin C. This lack of Vitamin C means that athletes’ immune systems aren’t performing as well and puts them at a greater risk of catching colds as well as other illnesses. By supplementing with daily Vitamin C, they get back to the immune system of the rest of the population and experience a reduction in the number of colds.

End Game

Based on the data, I wouldn't recommend buying any of those flashy products claiming to reduce your chances of getting a cold with the power of Vitamin C. Unless you are super athletic or in some other manner Vitamin C deficient and therefore catching more colds than the average person. But even then, just buy a simple supplement of Vitamin C, take 1 g per day, start now and keep taking it until it's tulip season, or keep going all year long if you like. Oh, and it should go without saying, but please always wash your hands so you can prevent yourself from catching someone's nasty cold in the first place.


  • Douglas, R., Chalker, E., & Treacy, B. (1998). Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews. doi:10.1002/14651858.cd000980
  • Murphy, C., Etzel, J. V., & Ambizas, E. M. (2017). Sorting Out Supplements for the Common Cold. U.S. Pharmacist, 41(4), 8-10.Vitamin C treatment for Common cold

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