Vitamin C has long been associated with its ability to combat viruses, particularly the common cold. While some might dismiss this as a myth, studies have shown that taking vitamin C before coming down with a cold can reduce the severity of symptoms and even shorten the duration of the illness. However, most clinical trials indicate that vitamin C only reduces the duration of a cold by approximately 10 percent. So, if you typically suffer from a cold for 10 days, vitamin C might reduce that down to nine days. While this isn’t exactly “miracle cure” territory, it may be that these clinical trials were not using high enough dosages of vitamin C to properly study its full effects.
The More Vitamin C, the Better
Most clinical trials studying the effect of vitamin C on colds provide participants with modest doses of the vitamin – typically around 1 gram (1,000 mg) per day. Interestingly, trials that use a dosage higher than 1 gram tend to yield better results. Researchers from the University of Helsinki in Finland decided to analyze two randomized trials that compared the effects of different doses of vitamin C on the common cold.
The first trial they examined compared the effect of 3 grams of vitamin C per day with the effect of 6 grams per day, finding that the 6 grams of vitamin C per day shortened the duration of colds by twice as much as 3 grams per day. Individuals who took 6 grams recovered 17 percent more rapidly than those who didn’t take any. The second study analyzed had similar findings, with one key difference: this time, researchers compared the effect of 4 grams of vitamin C per day with the effect of 8 grams per day. Again, a doubled dose produced double the effectiveness, with individuals taking 8 grams of vitamin C shortening the length of their cold by 19 percent.
These studies demonstrate that there is a dose-response relationship between vitamin C and the common cold – the more vitamin C you take, the better the results. Consequently, it may be possible that doses exceeding 8 grams per day could fight colds even more effectively. While additional research is required to confirm this, researchers do suggest that 8 grams of vitamin C should be sufficient to see a significant improvement in your cold symptoms.
Dr. Harri Hemilä from the University of Helsinki, who performed the analysis, said, “Given the consistent effect of vitamin C on the duration of colds, and its safety and low cost, it would be worthwhile for individual common cold patients to test whether therapeutic 8 g/day vitamin C is beneficial for them. Self-dosing of vitamin C must be started as soon as possible after the onset of common cold symptoms to be most effective.”
A Warning About High Doses of Vitamin C
If you’re thinking of increasing your vitamin C dose next time you have a cold, be cautious. While high doses of vitamin C are unlikely to pose any serious health risks (Linus Pauling, for example, took 18,000 mg of vitamin C daily and lived to be 93), it can cause diarrhea, nausea, and in rare cases, kidney stones.
If you’re looking for another vitamin to help make your colds less miserable and less frequent, consider exploring the cold-fighting properties of vitamin D too.
