Vitamin C and the Common Cold

The prevention and treatment of the common cold has been one of the most popular and tested applications of high-dose Vitamin C. While mainstream sources point to limited efficacy, the in-depth studies show the highest doses tend to produce the best results — and with a focused regimen for both prevention and treatment it can be easy to experiment on a personal basis. That’s a conclusion that can be somewhat difficult to parse from the published reports, however, particularly when simplified for popular consumption.

As an example, Harri Hemilä of the University of Helsinki in Finland, has led a periodically updated research review titled “Vitamin C for preventing and treating the common cold (Review)” that is one of the most comprehensive examinations of the topic available. Despite signals of stronger results from higher doses , the study’s somewhat ambiguous conclusions point to a reluctance to support an absolute recommendation for high-dose supplementation.

“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, yet vitamin C may be useful for people exposed to brief periods of severe physical exercise,” the study says. “Regular supplementation trials have shown that vitamin C reduces the duration of colds, but this was not replicated in the few therapeutic trials that have been carried out. Nevertheless, given the consistent effect of vitamin C on the duration and severity of colds in the regular supplementation studies, and the low cost and safety, it may be worthwhile for common cold patients to test on an individual basis whether therapeutic vitamin C is beneficial for them.”

In a published response to the study dating to 2005, researcher Steve Hickey — one of the most prominent advocates of high-dosage Vitamin C — pointed out what he saw as a critical flaw — that none of the studies focused on timing the doses to ensure a consistently high level of Vitamin C in the blood.

“Douglas and Hemila have not shown that vitamin C is ineffective against the common cold, unless the doses used are both inadequate and inappropriate,” Hickey wrote. “They have, however, made clear that the previous 65 years of research has been based on a range of doses that are too small and too infrequent. Thus, the research to date may grossly underestimate the therapeutic value of vitamin C. Tests of appropriate dose levels and timing regimes are urgently required..”

Hemilä responded with a comment that went into more detail of Vitamin C’s impact than the published conclusion, highlighting the impact of higher doses.