Vitamin D has the properties of both a vitamin and a hormone and is a fat-soluble vitamin which means that it is absorbed through the intestinal tract by means of lipids. Vitamin D is required for the absorption and utilization of calcium and phosphorus

Uses
Vitamin D is important for growth and it is especially important for the normal development and growth of bones and teeth in children. Vitamin D, similar to most other vitamins, has a multitude of uses. Vitamin D is important for protection against muscle weakness and the regulation of the heartbeat. However a deficiency of vitamin D can cause rickets in children and osteomalacia, which is a similar disease, in adults. This is however only in severe cases. In less severe cases a deficiency could be characterized by a loss of appetite, soreness in the mouth and throat, diarrhoea, insomnia, visual problems and unexplained weight loss. Children nowadays are becoming more and more deficient in vitamin D as they have a lack of outdoor activity and more aversion to drinking milk. There are various forms of vitamin D and unfortunately, the form that we intake from food or supplements is not fully active. This means that it requires conversion by the liver and then the kidneys in order for it to become fully active. This is why people with liver or kidney problems often have a deficiency of vitamin D and are therefore at higher risk of osteoporosis.

Sources
Vitamin D can be found naturally in fish liver oils, dairy products and eggs. Some other things that contain vitamin d are shiitake and chanterelle mushrooms, oysters, salmon, sardines, mackerel, butter and herbs like alfalfa, nettle, horsetail and parsley. Vitamin D, unlike vitamin C, is produced by the body in response to sunlight on the skin.