Will Extra Vitamin C Prevent Colds?

This year, some people suffered from summer colds, although these respiratory infections appear to be more common in other seasons. Every winter, millions of people suffer with congestion, coughs, fever and other symptoms of the common cold. They may lose days from work. (If they don’t take time off, they spread the virus causing the cold to many other individuals.) But is there a way to prevent colds? Many people are interested in the potential of vitamin C.

Vitamin C Stopped Cold Short

Q. Around 1980 I was working at a major ad agency in Tucson. We had a big presentation for a possible new client scheduled for the next day when it was obvious to all that I was coming down with a cold. The office manager sent me home with some homework.

I was to take 1000 mg of vitamin C each hour. She said this was the “prescription” her own doctor had given her and that it stopped her cold in its tracks. I did as I’d been told (except I took 500 mg each half hour). That afternoon she called to check on me, and I told her that I felt fantastic. No more cold.

I have taken this vitamin C dosage at the first sign of cold symptoms ever since. I have not come down with a cold in so many years that I cannot even recall my last cold.

A. Linus Pauling proposed that ascorbic acid could be helpful in treating colds in his book, Vitamin C and the Common Cold (1970). Since then, scientists have been arguing about whether this might be true.

An article in the Polish Archives of Internal Medicine (Jan. 30, 2025) summarizes the evidence from randomized controlled trials.  According to the research, vitamin C rarely prevents colds. However, taking at least one gram daily can significantly shorten the duration of a cold and reduce the severity of the symptoms. Higher doses appear to work better.

Years of Using Vitamin C Against the Common Cold

Q. I have been taking vitamin C since I was 17 years old. My boyfriend at that time suggested it helps prevent the common cold.

I am much older now and still taking it. Colds are rare, but if I get one, I take 1000 mg vitamin C every four hours. It works every time, shortening the time I have symptoms. Sometimes when I feel symptoms coming on, I take vitamin C, and I don’t get the cold at all.

PS. I gave my children vitamin C when they were little, and they also rarely got colds.

A. The Nobel Prize-winning chemist, Dr. Linus Pauling, published his little paperback book, Vitamin C and the Common Cold, in 1970. Over the last 5 decades, scientists have argued about his premise that ascorbic acid is helpful against respiratory infections.

One of the more comprehensive reviews was published earlier this year in the Polish Archives of Internal Medicine (Jan. 30, 2025). The authors concluded that vitamin C can reduce the severity and duration of cold symptoms. They have less evidence that people taking vitamin C could avoid colds.

They state, however:

“…if a person suffers from frequent colds, it is reasonable to test individually whether he or she may benefit from vitamin C supplementation during the winter.”

This reader is not alone. Many others have used vitamin C to speed recovery from colds. Some are convinced that this helps them avoid infection as well.

Does Vitamin C Prevent Colds?

Q. My wife and I have been taking extra vitamin C after each meal for more than a dozen years. Despite being around people with colds, we have had none. We’ve had no side effects from the vitamin C.

A. Health professionals generally dismiss vitamin C to prevent colds. A review of 29 trials of vitamin C for colds concluded that vitamin C doesn’t seem to prevent colds for most people but it consistently reduces their duration and severity (Cochrane Database of Systematic Reviews, Jan. 31, 2013). Perhaps that is because vitamin C can increase the activity of the immune system (Journal of Biological Regulators and Homeostatic Agents, Apr-June, 2013).

More than 200 different viruses can cause cold symptoms, so we’re not surprised that vitamin C might not work against all of them. Along with vitamin C, zinc also enhances immunity and can help reduce the duration of cold symptoms (Annals of Nutrition & Metabolism, 2006). Two preliminary studies showed that supplementation with 1000 mg vitamin C and 10 mg zinc reduced the duration of runny nose significantly more than placebo (Journal of International Medical Research, 2012).

Was Vitamin C to Prevent Colds Disproven?

More than a decade ago, we got this question and responded to it.

Q. When the nurse in my doctor’s office asked me what supplements I take, I mentioned vitamin C and told him that I up the dose if I feel a cold coming on. He laughed and said that had been disproven ages ago.

I am convinced it works for me. What do you say?

A. Taking vitamin C for preventing colds has been controversial for decades, ever since Linus Pauling recommended this strategy back in 1970. Since then there have been numerous studies but only limited evidence that this vitamin actually prevents colds.

Studies among marathon runners and people under severe winter conditions show that vitamin C cuts the risk of a cold in half under these circumstances (Cochrane Database of Systematic Reviews, Jan. 31, 2013). Other research indicates that people taking vitamin C regularly, as you do, are sick for fewer days if they catch a cold.

For more information about a variety of strategies to treat cold symptoms, including ginger or elderberry tea, vitamin D and zinc, we offer our Guide to Colds, Coughs & the Flu. Vitamin C used in this way does not appear to have serious adverse effects, though some people may find that at high doses it causes diarrhea. At the time we first answered this question, we had not seen Dr. Hemilä’s research on the topic, which it makes it clear we should not dismiss vitamin C for treating colds.

Other Natural Treatments for Colds

We have written previously about other ways of preventing colds, especially handwashing and sanitizing surfaces that could spread cold viruses. Analysis of 34 clinical trials show that the Chinese herb Andrographis paniculata and a preparation of ivy, primrose and thyme are far better than placebo for controlling coughs from colds (Forschende Komplementarmedizin, online Dec. 14, 2015).  You’ll find a variety of other natural cold fighters in our eGuide to Colds, Coughs and the Flu.

If you wish to hear more about vitamin C to prevent colds, you could listen to our interview with Dr. Hemilä and Dr. Cullen, who has studied the use of high-dose IV vitamin C against cancer. It is Show 1431: Vitamin C Studies on Colds & Cancer Vindicate Linus Pauling.