PATHOLOGY

Detailed explanation-1: -In the presence of sunlight, a form of vitamin D3 called cholecalciferol is synthesized from a derivative of the steroid cholesterol in the skin. The liver converts cholecalciferol to calcidiol, which is then converted to calcitriol (the active chemical form of the vitamin) in the kidneys.

Detailed explanation-2: -The epidermis is the major source of vitamin D for the body. Under the influence of sunlight (ultraviolet radiation, action spectrum 280–320nM or UVB) 7-dehydrocholesterol in the epidermis is converted to vitamin D.

Detailed explanation-3: -Because it’s so easily absorbed by the skin, many cosmetic manufacturers use this ingredient as a skin conditioner and moisturizer, especially in SPF products, which limit the body’s UVB exposure and, consequently, its vitamin D3 production.

Detailed explanation-4: -The skin is responsible for producing vitamin D. During exposure to sunlight, ultraviolet radiation penetrates into the epidermis and photolyzes provitamin D3 to previtamin D3. Previtamin D3 can either isomerize to vitamin D3 or be photolyzed to lymisterol and tachysterol.

Detailed explanation-5: -Most of this UVB radiation is absorbed in the epidermis and as a result when exposed to sunlight most of the vitamin D3 that is produced in the skin is made in the living cells in the epidermis.