Facts

Vitamin D is a fat-soluble vitamin acquired either by ingestion or exposure to sunlight. Often referred to as the "sunshine vitamin" because the sun's ultraviolet rays activate a form of cholesterol found in the skin, which it then converts to vitamin D.1

Functions

	Vitamin D aids in the absorption of calcium from the intestinal tract and the absorption and assimilation of phosphorous.
	Especially important for children, it is necessary for the normal growth and development of teeth and bones.2
	It is also necessary for: regulation of the heartbeat, prevention of osteoporosis. It also enhances immunity and is necessary for thyroid function and normal blood clotting.2

Requirements
The Recommended Daily Allowance has been set at 5 µg for Vitamin D.


Signs of Deficiency
Severe deficiency can cause rickets in children and osteomalacia, a similar disorder in adults, osteoporosis. Less severe symptoms include: loss of appetite, diarrhoea, insomnia and visual problems.2

Signs of Toxicity
Large intakes of vitamin D over an extended period of time can cause: headache, nausea, weakness and, in severe cases, calcification of soft tissue and mental retardation.


Note:
According to Mildred Seelig, M.D., Master of the American College of Nutrition and MRI's consultant, dietary imbalances such as a high ratio of vitamin D, phosphate and fat can increase one's susceptibility to developing a magnesium deficiency. "Later in infancy and in childhood, a low dietary magnesium to vitamin D ratio might contribute, as well, to more generalised atherosclerosis, hyperlipidemia, hypercalcemia, and hypertension."3


Current Research

Cancer
Vitamin D may be helpful in the prevention and treatment of some forms of cancer. Calcitrol, the active form of vitamin D, has been shown to inhibit the growth of human melanoma (skin cancer), leukemia, breast, lymphoma and colon cancer cells.4 In one study that spanned nearly 20 years, the risk of dying from colourectal cancer was inversely associated with vitamin D and calcium consumption.5 5

Cardiovascular Disease
According to investigators at Brigham and Women's Hospital in Boston, Mass., vitamin D deficiency in post-menopausal women is linked with an increased risk of fracture. In a group of women with osteoporosis hospitalised with a hip fracture, researchers found that 50 % were found to be deficient in vitamin D.6

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