Vitamin C for preventing and treating the common cold.

Area of Science:

• Nutrition Science
• Public Health
• Clinical Trials

Background:

• The efficacy of Vitamin C (ascorbic acid) in preventing and treating the common cold has been debated for seven decades.
• Previous research presents conflicting evidence regarding Vitamin C's role in managing cold symptoms.

Purpose of the Study:

• To evaluate the effectiveness of Vitamin C supplementation in reducing the incidence, duration, and severity of the common cold.
• To compare continuous daily supplementation versus therapy initiated at the onset of cold symptoms.

Main Methods:

• Systematic review and meta-analysis of placebo-controlled trials.
• Searched multiple databases (CENTRAL, MEDLINE, EMBASE, etc.) up to November 2012.
• Included trials using at least 0.2 g/day of Vitamin C, focusing on randomized, double-blind studies.

Main Results:

• Regular Vitamin C intake did not significantly reduce cold incidence in the general population (RR 0.97).
• However, it reduced cold duration by 8% in adults and 14% in children, and also decreased severity.
• A significant reduction in cold incidence (RR 0.48) was observed in individuals under extreme physical stress (e.g., marathon runners, soldiers).
• Therapeutic use of Vitamin C at symptom onset showed no consistent effect on duration or severity.

Conclusions:

• Routine Vitamin C supplementation is not recommended for preventing colds in the general population.
• Vitamin C may benefit individuals exposed to severe physical exercise by reducing cold incidence.
• Regular supplementation shortens cold duration and lessens severity, suggesting potential individual benefit for therapeutic use, though further trials are needed.