The purpose of this research is to study whether vitamin D supplement can improve clinical outcome (PASI score) in psoriasis vulgaris with vitamin D insufficiency and deficiency.

While psoriasis is not a lethal disease, the disease itself can impact patients' quality of life. Nowadays there are several researches on vitamin D functions. Recently review article of vitamin D deficiency by Holick MF., stated that vitamin D can play a role in decreasing the risk of osteoporosis and other chronic diseases such as malignancy, autoimmune disease, infectious disease, cardiovascular disease, and psoriasis. Moreover, vitamin D effects on keratinocyte by decreasing abnormal cell proliferation, differentiation, apoptosis and controlling immunological process via the suppression of T-cell activation, regulation of cytokine secretion patterns, induction of regulatory T-cell, modulation of T-cell proliferation and interference with T-cell apoptosis.

Thus, our objective is to look for other alternative treatment, which may have less side effects and acceptable clinical outcomes.

Inclusion Criteria:

• Mild to moderately severe (PASI ≤ 10), chronic plaque type psoriasis vulgaris patient, who is a new case or has at least treatment-free period as following: 4 weeks for topical calcipotriol, topical corticosteroid or 8 weeks for systemic therapy (i.e. cyclosporine, acitretin, methotrexate) or 12 weeks for Psoralen Ultraviolet A (PUVA), phototherapy or biological treatment.
• Age 18-year-old to 70-year-old.
• Psoriasis vulgaris patient with vitamin D insufficiency or deficiency.

Exclusion Criteria:

• Pregnancy or Lactating mother.
• Subject with history of major gastrointestinal surgery or gastric bypass surgery.
• Subject with history of pustular psoriasis.
• Subject with active psoriatic arthritis.
• Subject with prior phototherapy within the past 3 months.
• Subject with history of hypocholesterolemia (serum cholesterol < 120 mg/dl) or primary hyperparathyroidism.
• Subject who regularly takes vitamin D supplement exceed 3,000 iu/day and high vitamin D diet, for example cod liver oil.
• Subject with liver disease, cystic fibrosis, Crohn's disease, celiac sprue, renal disease, pancreatic disease, and inflammatory bowel disease.
• Subject taking following medication: corticosteroid, orlistat, rifampicin, isoniazid, ketoconazole, statin, and cholestyramine.