Definition
Vitamin D is a precursor to a steroid hormone that regulates calcium metabolism and affect mineralization of bone tissue.
In addition, regulates the vitamin D hormone cell division in many tissues, including skin and immune system.
The vitamin can be produced in the skin by injection of sufficient UVB radiation from the sun, or consumed by a limited number of sources in the diet: fatty fish, fish liver oil (cod liver oil), and milk, margarine and butter added vitamin D. In the winter months can be little or no vitamin D produced in skin in Norway because inadequate doses of UVB reaching the Earth's surface. Classical consequences of severe vitamin D deficiency is rickets in children and osteomalacia in adults, which provides soft bones, pain and weakness. Vitamin D status is measured by the concentration of 25-hydroxyvitamin D in serum or plasma. There is no general consensus on what constitutes optimal vitamin D status and where to set limits for deficiency, but a common definition is to regard levels below 12.5 nmol / l as severe vitamin D deficiency consistent with rickets, under 25 nmol / l (moderate) vitamin D deficiency, and below 50 nmol / l vitamin D insufficiency or insufficient vitamin D status.
Deficiency disease resulting from severe vitamin D deficiency is rickets in children and osteomalacia in adults. Milder vitamin D deficiency in adults may also contribute to loss of bone mass with osteopenia and osteoporosis to follow, leading to increased risk of fracture. These conditions are classified by WHO as risk conditions, and not as a disease. Recent studies have also shown that vitamin D deficiency in young can increase fat storage process and break down muscle.
Risk Factors
Known risk factors for vitamin D deficiency are:
Migration to northern latitudes
Season (winter half year)
Stay indoors and in the shade
Clothing, covering of skin
Melaninpigmentering (dark color)
Low intake of vitamin D-containing foods or supplements
Prolonged exclusive breast milk feeding