Does vitamin c prevent colds
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The Role of Vitamin C in Preventing and Treating the Common Cold
Vitamin C and Cold Incidence
The question of whether vitamin C can prevent the common cold has been a topic of debate for decades. Multiple studies have investigated this, with mixed results. A comprehensive review of 30 trials found that long-term daily supplementation with high doses of vitamin C (up to 1 gram daily) did not consistently reduce the incidence of colds in the general population1. Similarly, another meta-analysis involving 11,306 participants concluded that routine vitamin C supplementation does not significantly reduce the risk of developing a cold in the general community3. However, there is evidence suggesting that vitamin C may reduce the incidence of colds in specific groups exposed to extreme physical stress, such as marathon runners, skiers, and soldiers in sub-arctic conditions, with a pooled relative risk (RR) of 0.502 4.
Vitamin C and Cold Duration
While vitamin C may not prevent colds in the general population, it appears to have a modest effect on reducing the duration of cold symptoms. Several studies have shown that regular vitamin C supplementation can shorten the duration of colds by approximately 8% in adults and up to 14% in children2 3 4. This reduction translates to about half a symptom day per cold episode1. A meta-analysis of nine randomized controlled trials also found that extra doses of vitamin C at the onset of cold symptoms could further reduce the duration of the cold6.
Vitamin C and Cold Severity
The severity of cold symptoms can also be influenced by vitamin C intake. Regular supplementation has been shown to reduce the severity of colds, as measured by days confined indoors, off work or school, and symptom severity scores2 3. One study reported that volunteers taking vitamin C had significantly fewer days with severe symptoms compared to those taking a placebo5. However, when vitamin C is taken only after the onset of cold symptoms, the evidence for its effectiveness in reducing severity is less consistent2 4.
Therapeutic Use of Vitamin C
The therapeutic use of vitamin C, meaning its administration after the onset of cold symptoms, has shown mixed results. Some studies indicate no significant difference from placebo in reducing the duration or severity of colds when vitamin C is used therapeutically2 3 4. However, there is some evidence suggesting that very high doses (up to 8 grams daily) may offer some benefit, although this finding is not universally supported10.
Conclusion
In summary, while routine vitamin C supplementation does not appear to prevent the common cold in the general population, it may be beneficial for individuals exposed to extreme physical stress. Regular vitamin C intake can modestly reduce the duration and severity of cold symptoms. The therapeutic use of vitamin C after the onset of symptoms shows less consistent benefits, and further research is needed to clarify its role. Given its low cost and safety, individuals may consider testing vitamin C supplementation on a personal basis to see if it offers them any benefit.
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Most relevant research papers on this topic
Vitamin C for preventing and treating the common cold.
Long-term daily supplementation with high doses of vitamin C does not prevent colds, but may slightly reduce the duration of cold symptoms.
Systematic Review
Highly CitedVitamin C for preventing and treating the common cold.
Oral vitamin C in doses of 200 mg or more daily reduces the incidence, duration, and severity of common colds when used as continuous prophylaxis or after the onset of symptoms.
Meta-AnalysisHighly CitedVitamin C for preventing and treating the common cold.
Vitamin C supplementation does not reduce the incidence of colds in the general population, but may be useful for people exposed to brief periods of severe physical exercise.
Meta-Analysis
Very Rigorous JournalVitamin C for preventing and treating the common cold.
Vitamin C supplementation fails to reduce common cold incidence in the general population, but may be beneficial for people exposed to brief periods of severe physical exercise or cold environments.
Meta-AnalysisPreventing the common cold with a vitamin C supplement: A double-blind, placebo-controlled survey
A well-tolerated vitamin C supplement may help prevent common colds and shorten the duration of symptoms, with volunteers reporting increased satisfaction compared to previous forms of vitamin C.
RCTExtra Dose of Vitamin C Based on a Daily Supplementation Shortens the Common Cold: A Meta-Analysis of 9 Randomized Controlled Trials
Extra doses of vitamin C, despite routine supplementation, may help reduce the duration of colds and relieve symptoms, such as chest pain, fever, and chills.
Meta-Analysis
Rigorous JournalHighly CitedA CONTROLLED CLINICAL TRIAL OF ASCORBIC ACID FOR THE COMMON COLD
High doses of vitamin C can reduce the frequency and severity of colds in healthy, middle-class individuals, but their effectiveness in preventing colds remains unclear.
RCTCommon cold and vitamin C.
Vitamin C reduces symptom association and severity of colds in girls, but does not benefit boys at a daily dose of 500 mg, with a more pronounced effect during catarrhal colds.
RCTDoes vitamin C prevent the common cold?
Consumption of vitamin C does not prevent the incidence of common cold.
Meta-AnalysisVitamin C and Infections
Vitamin C may alleviate or prevent infections caused by bacteria, viruses, and protozoa, and may shorten the duration of colds in physically active individuals.
Literature ReviewVery Rigorous JournalHighly Cited