| Methods |
Double‐blind RCT. Regular supplementation trial. Duration 40 days |
| Participants |
UK adults. 121 vitamin C; 123 placebo |
| Interventions |
1 g/d vitamin C |
| Outcomes |
Incidence (Analysis 1.1) |
| Notes |
— |
| 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 |
"tablets or matching lactose dummies" |
