Vitamin D and Psoriasis

Vitamin D is one of the few conditions where the compound is genuinely first-line therapy. Topical vitamin D analogues (calcipotriene, calcitriol) are standard-of-care for mild-to-moderate plaque psoriasis, and narrowband UVB phototherapy leverages the same pathway. The role of oral cholecalciferol as an adjunct is more modest but supportive.

How vitamin D works in psoriasis

Psoriasis is a Th17-driven autoimmune condition characterised by keratinocyte hyperproliferation. Active 1,25-dihydroxyvitamin D binds to VDR in keratinocytes, inhibiting proliferation, promoting differentiation, and dampening the local inflammatory response. Topical calcipotriene delivers this activity directly to the plaque without raising serum calcium.

Topical calcipotriene / calcitriol

Calcipotriene 0.005% ointment or cream, applied twice daily to plaques, produces clearance in ~50–60% of patients over 8 weeks — comparable to mid-potency topical corticosteroids but without steroid side effects. Combination products with a corticosteroid (calcipotriene + betamethasone) are the current first-line topical approach in most guidelines.

Narrowband UVB phototherapy

Narrowband UVB at 311 nm is close to the peak vitamin-D-producing wavelength (297 nm) and is one of the most effective non-biologic psoriasis treatments — 80%+ clearance in moderate-to-severe plaque psoriasis over 12 weeks. It works through both direct immunosuppression and cutaneous vitamin D synthesis; patients often see substantial rises in serum 25(OH)D.

Oral cholecalciferol as adjunct

Psoriasis patients are commonly vitamin D deficient. Meta-analyses of oral supplementation (typically 1,000–4,000 IU/day cholecalciferol) show modest reductions in PASI (Psoriasis Area and Severity Index) — average 3–5 points over 12 weeks. This is small compared to topical calcipotriene or phototherapy, but low-cost and low-risk.

Atopic dermatitis (eczema)

Eczema patients also have lower average 25(OH)D than controls, and correcting deficiency modestly reduces eczema severity in randomised trials, particularly in children. The effect is smaller than for psoriasis. Vitamin D is not a substitute for standard eczema therapy (emollients, topical steroids or calcineurin inhibitors) but is a safe adjunct.

Practical approach

• For psoriasis: prescription topical calcipotriene (usually with a corticosteroid) is first-line for limited disease. Consult a dermatologist.
• Consider narrowband UVB phototherapy for moderate-to-severe cases; discuss with dermatologist.
• Test serum 25(OH)D and correct any deficiency with 2,000–4,000 IU/day cholecalciferol — adjunct, not primary therapy.
• For eczema: continue standard care; add cholecalciferol 1,000–2,000 IU/day if deficient.
• Sensible sun exposure (short, non-burning midday sessions) may help both conditions but must be balanced against long-term skin cancer risk.