Skin cancer and vitamins: In theory and practice.

Skin cancers are common malignant tumors with an increasing incidence worldwide. The major types are cutaneous malignant melanoma and keratinocytic tumors, such as basal cell carcinoma and cutaneous squamous cell carcinoma. The first treatment of choice is complete surgical removal, but nonsurgical treatment options and primary prevention may be requested. Vitamins may play a role in skin cancer prevention, because they are capable of reducing the deteriorating effects of sunlight (UV and visible light and infrared radiation) by scavenging reactive oxygen species. Patients with skin cancer are often undersupplied with certain vitamins such as vitamins C and D. Vitamin deficiency increases the risk for the primary development of skin cancer. Supplementation of certain vitamins supports conventional drug therapy in immunosuppressed patients and in those with advanced tumors under checkpoint inhibitor treatment. Supranormal vitamin C is prooxidative and prevents metastasis in animal models of cutaneous malignant melanoma.