Abstract
Sunlight exposure plays an important role in human health, impacting processes such as mood, blood pressure regulation, and vitamin D(3) production. Solar ultraviolet B radiation initiates vitamin D(3) synthesis in the skin, which is subsequently metabolized into its biologically active form. UVB exposure plays a key role in enabling vitamin D(3) 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 D(3) synthesis, the epidemiology of skin cancer, and the protective roles of vitamin D(3)'s photoproducts and its active metabolite, 1,25-dihydroxyvitamin D(3). Understanding these interconnections is critical for developing strategies that balance adequate sun-induced vitamin D(3) production with skin cancer prevention.