Vitamin C for preventing and treating the common cold

Area of Science:

• Nutrition Science
• Public Health
• Immunology

Background:

• Oral vitamin C (ascorbic acid) has been debated for decades regarding its effectiveness against the common cold.
• Despite controversy, public interest and usage of vitamin C for cold prevention and treatment remain high.

Purpose of the Study:

• To determine if daily oral vitamin C (≥200 mg) reduces common cold incidence, duration, or severity.
• To assess efficacy whether used as continuous prophylaxis or initiated after symptom onset.

Main Methods:

• Systematic review and meta-analysis of randomized controlled trials.
• Searched databases including CENTRAL, MEDLINE, and EMBASE up to June 2004.
• Included trials with ≥200 mg daily vitamin C, placebo comparison, and adequate outcome reporting.

Main Results:

• Prophylaxis with vitamin C did not significantly reduce cold incidence in the general population (RR 0.96).
• A subgroup of individuals under severe physical stress (e.g., marathon runners) showed a reduced incidence (RR 0.50).
• Vitamin C prophylaxis significantly reduced cold duration by 8% in adults and 13.5% in children, and severity.

Conclusions:

• Routine vitamin C prophylaxis is not recommended for the general population.
• Vitamin C may be beneficial for individuals facing extreme physical exercise or cold exposure.
• While not effective as a therapy initiated after cold onset, regular vitamin C intake appears to support respiratory defense mechanisms.