For adults with active plaque psoriasis, vitamin D supplementation does not affect psoriasis severity, according to a study published online March 29 in JAMA Dermatology.

Marita Jenssen, M.D., from the University Hospital of North Norway in Tromsø, and colleagues conducted a randomized clinical trial with two parallel groups performed through two winter seasons (2017 to 2018 and 2018 to 2019) to examine the effect of vitamin D supplementation on psoriasis severity. Participants were adults with active plaque psoriasis and 25-hydroxyvitamin D (25[OH]D) levels of less than 24 ng/mL who were randomly assigned to four months of vitamin D (cholecalciferol, 100,000 IU, loading dose, followed by 20,000 IU/week) or placebo.

Data were included for 122 participants: 60 and 62 were randomly assigned to the vitamin D and placebo groups, respectively; 120 (59 and 61, respectively) completed the study. The researchers found that the mean 25(OH)D levels were 29.7 and 12.0 ng/mL in the vitamin D and placebo groups, respectively. No significant between-group difference was seen in the change in Psoriasis Area and Severity Index (PASI) score. Furthermore, no significant difference was seen between the groups in the change in the Physician Global Assessment score, self-administered PASI, or Dermatology Life Quality Index. No intervention-related adverse events were reported.

"Based the findings of this randomized clinical trial, any large effect of vitamin D supplementation on psoriasis severity seems unlikely in those with mild disease (PASI <5)," the authors write.

One author disclosed financial ties to the pharmaceutical industry.