Vitamin C and the common cold: a double-blind trial

Area of Science:

• Nutrition Science
• Public Health
• Clinical Trials

Background:

• The common cold remains a significant public health concern with substantial economic impact.
• Vitamin C (ascorbic acid) has long been popularly believed to prevent or treat colds, but scientific evidence remains debated.
• Large-scale, rigorous trials are needed to clarify the efficacy of vitamin C supplementation for cold symptoms.

Purpose of the Study:

• To evaluate the effectiveness of daily one-gram vitamin C supplementation in reducing the frequency and duration of common colds.
• To assess the impact of vitamin C on illness-related disability and the proportion of subjects remaining illness-free.

Main Methods:

• A large-scale, double-blind, placebo-controlled trial was conducted.
• Participants were randomized to receive either one gram of vitamin C daily or a placebo.
• Outcomes measured included cold frequency, duration, days of sickness, and days of disability.

Main Results:

• No statistically significant reduction in the average number of colds or days of sickness per subject was observed.
• A statistically significant increase in the number of subjects remaining illness-free was found in the vitamin C group (P <0.05).
• Vitamin C supplementation led to a highly significant reduction (P <0.001) in total disability days (approximately 30%), primarily due to fewer constitutional symptoms.

Conclusions:

• While daily vitamin C supplementation at one gram did not significantly reduce cold incidence or duration, it enhanced resistance to illness and markedly decreased disability.
• The findings suggest vitamin C may play a role in mitigating the severity of acute illnesses, particularly constitutional symptoms, irrespective of respiratory involvement.