What role does Vitamin D 25-OH play in Haut?

Vitamin D (25-OH) plays a key role in skin health. It is synthesized in the skin via UVB exposure and regulates keratinocyte differentiation, barrier integrity, and cutaneous immune function. Deficiency is linked to dry skin, psoriasis, acne, and impaired wound healing. However, evidence for direct causal effects on specific skin conditions from randomized trials is limited; most data come from observational or mechanistic studies. A 25-OH level below 30 ng/mL is often considered suboptimal, but supplementation solely for skin benefits is not strongly supported. Always consult a dermatologist before using vitamin D supplements for skin issues. The provided context lacks direct studies on vitamin D and skin, so the evidence is rated as mechanistic/unclear.