Bucher A, White N. Am J Lifestyle Med. 2016 Feb 9;10(3):181-183
During the winter months, absenteeism or decreased productivity at work or school can often be attributed to symptoms of the common cold. Many people seek over-the-counter (OTC) products for their symptoms, and some of the commonly purchased products are those with high-dose supplements of vitamin C (ascorbic acid). The common cold causes enormous morbidity worldwide, and it is important to know the effects of vitamin C for both preventive and therapeutic purposes to correctly recommend the proper OTC product for these symptoms. The purpose of this article is to review the current data on the relationship between vitamin C and immune function, specifically, the utility of vitamin C supplementation in the prevention and treatment of the common cold.
Resource from https://www.ncbi.nlm.nih.gov/pubmed/30202272
While data do show a decreased severity and duration of colds when vitamin C is consumed at doses at or above 0.2 g/day, it is most reasonable for patients to obtain this from their diet, considering supplementation did not decrease the overall incidence of colds in the general population. Regular supplementation may have a place in special populations, specifically those under high physical stress and those with marginal vitamin C status.
Overall, while there is a wide variety of data available, there is a lack of consistency, and further study is necessary to provide clarity on the utility of vitamin C for therapeutic purposes. Given the low cost and relative safety of vitamin C supplementation, it is not unreasonable for patients experiencing cold symptoms to see for themselves if therapeutic vitamin C is beneficial, but they should know that the data behind its use are largely inconsistent. It appears the greatest potential for benefit of vitamin C in treating the common cold occurs when supplementation is initiated within 24 hours of symptom onset at high doses (~8 g daily) and when therapy is continued for at least 5 days.
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