| Methods |
Double‐blind RCT. 2 x 2 factorial: regular supplementation and therapeutic vitamin C. Duration 9 months. We compared 3 different arms with the placebo arm. This is regular supplementation arm |
| Participants |
USA, employees of the NIH. 44 vitamin C; 46 placebo |
| Interventions |
3 g/d vitamin C |
| Outcomes |
Duration (Analysis 2.1) |
| Notes |
The authors believed that the benefits observed were attributable to the breaking of the patient blind: "we discovered that some of the volunteers had tasted the contents of their capsules and professed to know whether they were taking the ascorbic acid or the placebo". However, their interpretation was later shown to be erroneous, seeHemilä 1996a, Hemilä 2006a, Hemilä 2006c
|
| 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? |
Unclear risk |
See Notes |
