Vitamin D is one of the fat-soluble vitamins, along with A, E, and K. Its metabolites can be classified into two families, the cholecalciferols and ergocalciferols. Cholecalciferol (vitamin D3), is the parent of the naturally occurring family and is produced in the skin on exposure to sunlight. The UVB portion of sunlight (290 to 315 nm) converts 7-dehydrocholesterol (provitamin D3) to vitamin D3, cholecalciferol. The liver converts D3 to 25-hydroxycalciferol (25-OH-D). The main function of vitamin D in the body deals with calcium absorption, transport, deposition and metabolism. Decreased levels can result in symptoms involving disturbed calcium use, nerve and muscle impairment, soft or fragile bones, or if severe enough, in the classic disease called rickets. An excellent source of vitamin D is sunshine on skin, 15 to 20 minutes a day. Other sources of vitamin D are butter, eggs, milk, cod liver oil and cold water fish.