Vitamin C for preventing and treating the common cold

  • Comment
  • Review
  • Intervention




Vitamin C (ascorbic acid) in preventing and treating the common cold has been a subject of controversy for 60 years.


To discover whether oral doses of 0.2 g per day or more of vitamin C reduce the incidence, duration or severity of the common cold when used as continuous prophylaxis (regularly every day) or as therapy after onset of symptoms.

Search methods

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, issue 1) which contains the Acute Respiratory Infections Group's Specialised Register, MEDLINE (2006 to February 2010) and EMBASE (2006 to February 2010).

Selection criteria

We excluded trials if a dose less than 0.2 g per day of vitamin C was used, or if there was no placebo comparison. We did not restrict to randomised controlled trials (RCTs).

Data collection and analysis

Two reviewers independently extracted data. 'Incidence' of colds during prophylaxis was assessed as the proportion of participants experiencing one or more colds during the study period. 'Duration' was the mean days of illness of cold episodes.

Main results

Twenty-nine trial comparisons involving 11,306 participants contributed to the meta-analysis on the risk ratio (RR) of developing a cold whilst taking prophylactic vitamin C. In the general community trials, involving 10,708 participants, the pooled RR was 0.97 (95% confidence interval (CI) 0.94 to 1.00). Five trials involving a total of 598 marathon runners, skiers and soldiers on subarctic exercises yielded a pooled RR of 0.48 (95% CI 0.35 to 0.64).

Twenty-nine comparisons examined the effect of prophylactic vitamin C on common cold duration (9649 episodes). In adults the duration of colds was reduced by 8% (3% to 12%), and in children by 13% (6% to 21%). The severity of colds was significantly reduced in the prophylaxis trials.

Seven trial comparisons examined the effect of therapeutic vitamin C (3249 episodes). No consistent differences from the placebo group were seen in the duration or severity of colds.

Authors' conclusions

The failure of vitamin C supplementation to reduce the incidence of colds in the general population indicates that routine prophylaxis is not justified. Vitamin C could be useful for people exposed to brief periods of severe physical exercise. While the prophylaxis trials have consistently shown that vitamin C reduces the duration and alleviates the symptoms of colds, this was not replicated in the few therapeutic trials that have been carried out. Further therapeutic RCTs are warranted.




維生素C(ascorbic acid)對感冒的預防與治療的功能這60年來未有定論。




我們搜尋Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, issue 1),它包含了Acute Respiratory Infections Group's Specialised Register、 MEDLINE (2006年 −2010年2月) 及 EMBASE (2006年 −2010年2月)。






共有29個試驗、 11,306位受試者被囊括在針對預防性投予維生素C對發生感冒的相對危險性之綜合分析中。在社區試驗、包含 10,708位受試者,其pooled RR為0.97(95%CI 0.94−1.00)。5個試驗,受試者是598位馬拉松運動員、滑雪選手、在近極地受訓的士兵,其相對風險為0.48(95%信賴區間為0.35 – 0.64)。 29個比較組檢驗了“感冒持續時間”,對預防性投予維生素C對發生感冒的綜合分析中,有9649人次的感冒被囊括進來分析,結果發現預防性給予維生素在成人及小孩都有縮短病程的效果;在成人可縮短8%的病程(95%信賴區間為3%12%),在小孩可縮短13%的病程(95%信賴區間為6%21%),而感冒的嚴重度顯著下降。 在出現感冒症狀才開始服用維生素C的部份,有7個試驗、3249 個人次的感冒被囊括進來,分析其病程,結果跟服用安慰劑的對照組並沒有顯著的差異。


一般人補充為他命C並無法預防感冒發生,因此常規服用並不合理。維他命C對於短時間短暫暴露於嚴峻的體能活動者有幫助。 儘管預防性試驗一向顯示維他命C對於縮短感冒流程及舒緩症狀有效,不過該效果卻無法同樣出現在治療性試驗上。尚待進一步的隨機對照試驗證明。



此翻譯計畫由臺灣國家衛生研究院(National Health Research Institutes, Taiwan)統籌。


維生素C對感冒的預防與治療。 雖然一般人對感冒的症狀很熟悉,”感冒“這個名詞並未被定義為某個特殊疾病。它是西方國家一般民眾就醫、或讓人無法正常上學上班的主因。它通常是呼吸道病毒所致,抗生素的治療是無效的,其他可能治療的方式將引起公共衛生方面的重大注意。 自從維生素C在1930年代被分離出來,就被建議用於呼吸道感染;到1970年代,諾貝爾講得主Linus Pauling根據早期的研究,提出大劑量的維生素C跟安慰劑比較可減少感冒的發生率的說法,維生素C的服用自此更廣受歡迎。從此之後進行了超過24個新試驗。維他命C被廣為販售,並且用作預防及治療藥劑。本文獻回顧只囊括有服用安慰劑可做對照組的試驗,且每天受試者須服用大> = 0.2g的維生素C。一般人常規補充為他命C並無法影響感冒發生。不過可以溫和、但持續縮短感冒病程及嚴重度。 5個受試者為短時間暴露在嚴峻的體能壓力者 (包含馬拉松選手與滑雪者)的試驗顯示維他命C可以減少一半感冒的風險。 至於針對治療性服用維生素C的研究則顯示,在感冒症狀出現後才開始服用者,對感冒持續的時間或嚴重程度並沒有一致的結果。然而治療性試驗數量太少;而且雖然預防性使用維他命C對於兒童有很大效果,但其中沒有一個是以兒童為檢驗對象。有一個大型的試驗報導,在症狀發生時開始服用8g的維生素C可能有效;另外兩個試驗則報導連續服用五天是有益的。 需要更多的試驗以確認治療性維他命C效用,意謂著一旦出現感冒症狀需立刻投與維他命C。

Plain language summary

Vitamin C for preventing and treating the common cold

The term 'the common cold' does not denote a precisely defined disease, yet the characteristics of this illness are familiar to most people. It is a major cause of visits to a doctor in Western countries and of absenteeism from work and school. It is usually caused by respiratory viruses for which antibiotics are useless. Other potential treatment options are of substantial public health interest.

Since vitamin C was isolated in the 1930s it has been proposed for respiratory infections. It became particularly popular in the 1970s when Nobel laureate Linus Pauling concluded from earlier placebo-controlled trials that vitamin C would prevent and alleviate the common cold. Over two dozen new trials were undertaken thereafter. Vitamin C has been widely sold and used as both a preventive and therapeutic agent.

This review is restricted to placebo-controlled trials testing 0.2 g per day or more of vitamin C. Regular ingestion of vitamin C had no effect on common cold incidence in the ordinary population. However, it had a modest but consistent effect in reducing the duration and severity of common cold symptoms. In five trials with participants exposed to short periods of extreme physical stress (including marathon runners and skiers) vitamin C halved the common cold risk.

Trials of high doses of vitamin C administered therapeutically, starting after the onset of symptoms, showed no consistent effect on either duration or severity of common cold symptoms. However, only a few therapeutic trials have been carried out, and none have examined children, although the effect of prophylactic vitamin C has been greater in children. One large trial with adults reported equivocal benefit from an 8 g therapeutic dose at the onset of symptoms, and two trials using five-day supplementation reported benefit. More trials are necessary to settle the possible role of therapeutic vitamin C, meaning administration immediately after the onset of symptoms.