Illuminating the Connection: Cutaneous Vitamin D₃ Synthesis and Its Role in Skin Cancer Prevention

Sunlight exposure plays an important role in human health, impacting processes such as mood, blood pressure regulation, and vitamin D₃ production. Solar ultraviolet B radiation initiates vitamin D₃ synthesis in the skin, which is subsequently metabolized into its biologically active form. UVB exposure plays a key role in enabling vitamin D₃ synthesis, but it can also contribute to skin carcinogenesis, creating a complex interplay between its beneficial and harmful effects. Vitamin D deficiency, affecting over half the global population, is linked to a range of chronic diseases, including cancers, cardiovascular conditions, and autoimmune disorders. Simultaneously, excessive solar UVB exposure increases the risk of non-melanoma and melanoma skin cancers through mechanisms involving DNA damage and oxidative stress. This review examines the dual role of UVB radiation in health and disease, focusing on the mechanisms of cutaneous vitamin D₃ synthesis, the epidemiology of skin cancer, and the protective roles of vitamin D₃'s photoproducts and its active metabolite, 1,25-dihydroxyvitamin D₃. Understanding these interconnections is critical for developing strategies that balance adequate sun-induced vitamin D₃ production with skin cancer prevention.