Functions of Vitamin D
Vitamin D helps regulate levels of calcium and phosphorus in blood. Vitamin D is necessary for the absorption of calcium from the intestinal tract reducing its urinary loss, and for the assimilation of phosphorus which is required in bone formation. The vitamin aids in the synthesis of enzymes in the mucous membranes that are involved in the transport of calcium. Since it affects growth of cells, adequate Vitamin D has been linked to reduction of breast, colon and prostate cancer. Vitamin D is involved in cell reproduction, blood cell formation, and enhances the immune system. It is needed for regulating glucose.
Deficiency disorders of Vitamin D
Long term deficiency of Vitamin D affects skeletal system. In children, deficiency of Vitamin D leads to rickets where bones weaken and bow under pressure. In adults, Vitamin D deficiency causes osteomalacia or soft bones and osteoporosis.
Disorders due to excess intake of Vitamin D
Excessive amounts may cause a rise of calcium and phosphorus in the blood and excessive excretion of calcium in the urine. This may lead to calcification of soft tissues and of the walls of the blood vessels and kidney tubules, a condition called hypercalcemia. Too much vitamin D for prolonged periods can result in weight loss, headaches, and kidney stones.
Sources of Vitamin D
Dietary sources of vitamin D are egg yolks, butter, fortified milk, fatty fish species including –catfish, salmon, mackerel, sardines, tuna, eel, and fish livers or oil, mushrooms. After absorption, vitamin D is transported to the liver for storage and deposits are found in the skin, brain, spleen, and bones.