Plasma 25(OH)D concentrations
An ANCOVA was performed to examine for an association between the final level of log transformed 25(OH)D and treatment group adjusting for the baseline log transformed plasma 25(OH)D concentration. The p-value for an interaction between baseline level and group was p = 0.2. The interaction was removed and the model was refitted. The model estimate, accounting for screening 25(OH)D level, was that, on average, the final plasma 25(OH)D concentrations were 2.66 times higher (95% CI: 1.98, 3.56) in the treatment group compared to the placebo group. Tables providing details regarding the ANOVA analyses are presented in Additional file 