Vitamin D aids in the absorption of calcium and phosphorous and in the regulation of bone mineralization.
Vitamin D is a hormone and a prehormone. Much of the needed amount of vitamin D can be acquired through sunlight, which converts precursors into the active form. In the body, vitamin D3 is converted into its hormonal forms; 1, 25 dihydroxy D3 and 24, 25 dihydroxy D3 through a process occurring in the liver and then kidneys, which performs the regulatory functions involved in bone mineralization. As in vitamin A, vitamin D is absorbed with fat.
Dietary sources of vitamin D include fatty fish, eggs, liver, butter and fortified milk and margarine.
In infants and young children, vitamin D deficiency may lead to rickets, a condition resulting in bone deformities.
In adults, deficiency may result in osteomalacia, a demineralization of bone affecting the spine, pelvis and legs.