Background/Aim: Vitamin D has anti-proliferative, pro-differentiative and immunomodulating effects. We aimed to determine whether raising serum 25(OH)D through vitamin D3 supplementation improves psoriasis.
Methods: In a randomised (2:1), double-blind, placebo-controlled trial, 101 participants >18y with plaque psoriasis took 200,000 International Units (IU) of cholecalciferol at baseline then 100,000 IU/month for 11 months (n=67), or placebo (n=34). Psoriasis Area and Severity Index (PASI) and serum 25(OH)D concentration were assessed at baseline, 3m, 6m, 9m and 12m. Primary outcomes were a) difference in PASI between groups over time, and b) the relationship between PASI and 25(OH)D over time, assessed by linear mixed models adjusted for confounding/individual factors.
Results: There was a significant inverse relationship between 25(OH)D and PASI. Elevating serum 25(OH)D by increments from 25 – 125nmol/L was associated with mild decreases in PASI (estimated range of decrease 0 – 2.6; P=0.002). PASI did not differ by group (P=0.62, group*time P=0.54), and an improvement in PASI of 50% or higher was achieved by 11.9% of treatment and 11.8% of placebo. However, mean 25(OH)D significantly increased from baseline at 3m for treatment (b = 33 [95% CI 28 – 38] nmol/L, P<0.001) and 6m for placebo (b = 24 [95% CI 17 – 30] nmol/L, P<0.001), possibly confounding these results.
Conclusion: At a population level, elevating serum 25(OH)D is associated with improved psoriasis. Estimated improvements were mild at 25(OH)D concentrations in this study and may not be clinically significant; higher concentrations could have greater benefit.
Funding sources: Lottery Health Research, Massey University