| Methods |
Placebo‐controlled alternative‐allocation trial. Therapeutic trial |
| Participants |
US college students. 179 vitamin C, 119 placebo; 206 with nose colds and 92 with throat colds |
| Interventions |
1 g vitamin C at first examination at the start of the cold and then 1 g 24 hours later |
| Outcomes |
"Colds that did not develop" meaning that the cold lasted only a day. In contrast, those who still had symptoms on the next day were considered to have a cold. (Table 7) |
| Notes |
Alternate allocation is not consistent with the distribution of participants in the vitamin C and placebo groups |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Random sequence generation (selection bias) |
Unclear risk |
"alternately" |
| Allocation concealment (selection bias) |
Unclear risk |
? |
| Blinding of participants and personnel (performance bias)
All outcomes |
Unclear risk |
"given... without knowledge on the subjects' part that placebos were being given." Indicates single‐blinding |
| Blinding of outcome assessment (detection bias)
All outcomes |
Low risk |
Subjects' observed outcome |
| Incomplete outcome data (attrition bias)
All outcomes |
Unclear risk |
? |
| Vitamin C and placebo indistinguishable? |
Low risk |
"citric acid as a placebo" |
