title: Sunlight, ultraviolet radiation, vitamin D and skin cancer: how much sunlight do we need?
abstract: Vitamin D is the sunshine vitamin for good reason. During exposure to sunlight, the UV B photons enter the skin and photolyze 7-dehydrocholesterol to previtamin D3 which in turn is isomerized by the body's temperature to vitamin D3. Most humans have depended on sun for their vitamin D requirement. Skin pigment, sunscreen use, aging, time of day, season and latitude dramatically affect previtamin 13 synthesis. Vitamin D deficiency was thought to have been conquered, but it is now recognized that more than 50% of the world's population is at risk for vitamin D deficiency. This deficiency is in part due to the inadequate fortification of foods with vitamin D and the misconception that a healthy diet contains an adequate amount of vitamin D. Vitamin D deficiency causes growth retardation and rickets in children and will precipitate and exacerbate osteopenia, osteoporosis and increase risk of fracture in adults. The vitamin D deficiency has been associated pandemic with other serious consequences including increased risk of common cancers, autoimmune diseases, infectious diseases and cardiovascular disease. There needs to be a renewed appreciation of the beneficial effect of moderate sunlight for providing all humans with their vitamin D requirement for health.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Holick
mesh_terms: D000375:Aging / Q000378:metabolism*; D001851:Bone Diseases, Metabolic / Q000378:metabolism / Q000517:prevention & control; D002762:Cholecalciferol / Q000031:analogs & derivatives / Q000378:metabolism; D003684:Dehydrocholesterols / Q000378:metabolism; D006801:Humans; D010024:Osteoporosis / Q000378:metabolism / Q000517:prevention & control; D010782:Photolysis; D012279:Rickets / Q000378:metabolism / Q000517:prevention & control; D012867:Skin / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D012878:Skin Neoplasms / Q000378:metabolism* / Q000517:prevention & control; D012880:Skin Pigmentation / Q000528:radiation effects; D013472:Sunlight; D013473:Sunscreening Agents / Q000009:adverse effects; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000008:administration & dosage / Q000378:metabolism*; D014808:Vitamin D Deficiency / Q000178:diet therapy / Q000378:metabolism*
chemical_list: D003684:Dehydrocholesterols; D013473:Sunscreening Agents; D014807:Vitamin D; D002762:Cholecalciferol; C016705:7-dehydrocholesterol; C025168:previtamin D(3)