Vitamin D (or calciferol) is a fat-soluble vitamin. It is a generic term and refers to a group of fat-soluble compounds with a four-ring cholesterol structure. Dermal synthesis, under the action of UV-B light on the skin, is the main natural source of this vitamin, as very few foods contain vitamin D naturally (fatty fish, such as salmon, tuna, sardines, trout, are the exception). This vitamin D, whether derived from the diet or dermal synthesis, is biologically inactive. It is […]