Effect of vitamin C on common cold: randomized controlled trial.
OBJECTIVE
To investigate the relationship between the common cold and vitamin C supplementation.


METHODS
A double-blind, 5-year randomized controlled trial.


METHODS
A village in Akita prefecture, one of the regions in Japan with the highest mortality from gastric cancer.


METHODS
Participants in annual screening programs for circulatory diseases conducted under the National Health and Welfare Services Law for the Aged, and diagnosed as having atrophic gastritis. Of the 439 eligible subjects, 144 and 161 were assigned to receive 50 or 500 mg of vitamin C, respectively, after protocol amendment. During the supplementation phase, 61 dropped out, and 244 completed the trial.


METHODS
Daily vitamin C supplementation of 50 mg (low-dose group) or 500 mg (high-dose group).


RESULTS
Total number of common colds (per 1000 person-months) was 21.3 and 17.1 for the low- and high-dose groups, respectively. After adjustment for several factors, the relative risks (95% confidence interval (CI)) of suffering from a common cold three or more times during the survey period was 0.34 (0.12-0.97) for the high-dose group. No apparent reduction was seen for the severity and duration of the common cold.


CONCLUSIONS
A randomized, controlled 5-year trial suggests that vitamin C supplementation significantly reduces the frequency of the common cold but had no apparent effect on the duration or severity of the common cold. However, considering several limitations due to protocol amendment, the findings should be interpreted with caution.
Sasazuki
S
S
Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Chuo-ku, Tokyo, Japan. ssasazuk@gan2.res.ncc.go.jp
Sasaki
S
S
Tsubono
Y
Y
Okubo
S
S
Hayashi
M
M
Tsugane
S
S
D000328:Adult; D000368:Aged; D000975:Antioxidants / Q000008:administration & dosage / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D003139:Common Cold / Q000453:epidemiology*; D016001:Confidence Intervals; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012720:Severity of Illness Index; D013997:Time Factors
D000975:Antioxidants; D001205:Ascorbic Acid