| Methods |
Double‐blind RCT. Regular supplementation trial. Duration 2 to 3 weeks |
| Participants |
Canadian male military recruits during subarctic winter exercises. 56 vitamin C; 56 placebo |
| Interventions |
1 g/d vitamin C |
| Outcomes |
Incidence (Analysis 1.1) and duration (Analysis 2.1) |
| Notes |
Personal communication from Manny Radomski (12 September 2009): "Tent group commanders [who were responsible for distributing the pills and recording the distribution] did not know what was in the vials... We [the authors] collected the data by symptoms on T‐scan cards. We did not 'break the code' until after all cards had been assessed." |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Random sequence generation (selection bias) |
Low risk |
Randomised |
| Allocation concealment (selection bias) |
Low risk |
Double‐blind |
| Blinding of participants and personnel (performance bias)
All outcomes |
Low risk |
Double‐blind |
| Blinding of outcome assessment (detection bias)
All outcomes |
Low risk |
Double‐blind |
| Incomplete outcome data (attrition bias)
All outcomes |
Low risk |
|
| Vitamin C and placebo indistinguishable? |
Low risk |
Personal communication (Radomski 12 September 2009): "Vitamin C and placebo were in identical capsules, so taste did not enter into the equation... In our pre‐briefing to the troops, we believe that we told the troops that they would all be getting vitamin C but at different doses." |
