(written as vitamin D)A fat-soluble vitamin (calciferol) whose main function is regulating calcium and phosphate metabolism (bone formation and repair). It is not normally present in nature but its precursors or provitamins, vitamin D2 and D3 are found in milk, cheese, eggs, butter, margarine (fortified) and especially oily sea fish. These provitamins are converted in the body to vitamin D by the action of sunlight. Lack of vitamin D causes rickets (deformation of the bones) in children and liability to fracture in adults. The vitamin is toxic in excess, 30,000 IU for adults and 2,000 IU for children.
- noun a vitamin which is soluble in fat and is found in butter, eggs and fish. It is also produced by the skin when exposed to sunlight. It helps in the formation of bones, and lack of it causes rickets in children.