Vitamin D, ultraviolets and skin cancer The vitamin D supply is fundamental for the prevention of falls and fractures in aged people, among other effects. UVB triggers vitamin D synthesis in the skin. This relationship has recently gained attention both with the general public and with health care professionals. Some authors suggest a relaxation of UV protection measures, while others even advocate regular sunlight exposure in order to increase cutaneous vitamin D synthesis. However, the UV irradiation responsible for vitamin D synthesis also is a known carcinogen. UV exposure is an insufficient and harmful method to increase vitamin D synthesis. Oral supplementation is the recommended way to prevent and cure vitamin D deficiency.