D2-derived from plant sources

D3-derived from animal sources

Function: It promotes calcium and phosphorous absorption from intestines, increases calcium deposition into bones, mobilizes calcium and phosphorous from bones. It prevents certain cancers and is required for proper thyroid function.

Sources: Cod liver oil, cold-water fish (salmon, herring, sardines, mackerel), milk (fortified with vitamin D), egg yolk, small amounts in dark-green leafy vegetables and mushrooms. Sunlight is converted into vitamin D.

Optimal Intake: 400 to 800 IU

Deficiency Signs: Rickets-softening of the skull bones, bowing of the legs, spinal curvature, a contracted pelvis, abnormal enlargement of the head, and an increased joint space; delayed tooth eruption; osteoporosis

Toxicity: Nausea, anorexia, weakness, headache, digestive disturbance, kidney damage, calcification of soft tissues, and hypercalcemia