The Vitamin D and Psoriasis Study

INTERVENTION: 200,000 IU of vitamin D3 in capsule form at baseline, then 1 x 100,000 IU per month for the next 11 months. CONDITION: Psoriasis vulgaris PRIMARY OUTCOME: Change in Psoriasis Area and Severity Index (PASI) scores in treatment group compared to placebo group. Change in serum 25(OH)D levels and PASI scores according to different vitamin D receptor genetic polymorphisms. SECONDARY OUTCOME: Change in inflammatory marker levels in the treatment group compared to the placebo group. Quality of life as assessed using the Dermatology Life Quality Index questionnaire. INCLUSION CRITERIA: Medically diagnosed psoriasis vulgaris