Quick guide to Vitamin D
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- the absorption and use of calcium and phosphorus, which are vital for functions such as the development of bones and teeth
- healthy nervous and immune systems
- regulation of some hormones
- normal cell growth and maturation
Absorption and metabolism
Vitamin D requires fat for absorption. It is also made in the skin.
Deficiency
Deficiency in children leads to rickets in which bones lose calcium and become soft and curved. In adults, symptoms include bone pain and tenderness, and muscle weakness. Deficiency may also increase the risk of osteoporosis, arthritis and cancer.
Sources
Good sources include fortified milk, oily fish, liver and eggs.
Daily recommended dietary intakes
- Men 200 IU
- (over 50) - 400 IU
- (over 70) - 600 IU
- Women - 200 IU
- (over 50) - 400 IU
- (over 70) - 600 IU
- Pregnancy - 200 IU
- Lactation - 200 IU
Toxic effects of excess intake
These include symptoms of unusual thirst, sore eyes, itching skin, vomiting, diarrhea, and eventually, calcium deposits in the blood vessels, lungs and kidney.
Therapeutic uses of supplements
Supplements have been used to treat osteoporosis and osteoarthritis in elderly people. Synthetic vitamin D analogues are used to treat psoriasis.
Interactions
Cholestyramine, anticonvulsants, alcohol and mineral oil interfere with the action of vitamin D.